Download Reproduction and Genetics

Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
Science Grade 07 Unit 11 Exemplar Lesson 01: Reproduction and Genetics
This lesson is one approach to teaching the State Standards associated with this unit. Districts are encouraged to customize this lesson by supplementing
with district-approved resources, materials, and activities to best meet the needs of learners. The duration for this lesson is only a recommendation, and
districts may modify the time frame to meet students’ needs. To better understand how your district may be implementing CSCOPE lessons, please contact
your child’s teacher. (For your convenience, please find linked the TEA Commissioner’s List of State Board of Education Approved Instructional Resources
and Midcycle State Adopted Instructional Materials.)
Lesson Synopsis
Students will define heredity, compare the results of offspring from sexual and asexual reproduction, and recognize that inherited traits of individuals are
governed in the genetic material found in genes.
TEKS
The Texas Essential Knowledge and Skills (TEKS) listed below are the standards adopted by the State Board of Education, which are required by Texas
law. Any standard that has a strike-through (e.g. sample phrase) indicates that portion of the standard is taught in a previous or subsequent unit. The
TEKS are available on the Texas Education Agency website at http://www.tea.state.tx.us/index2.aspx?id=6148.
7.14
Organisms and environments. The student knows that reproduction is a characteristic of living organisms and that the
instructions for traits are governed in the genetic material. The student is expected to:
7.14A Define heredity as the passage of genetic instructions from one generation to the next generation.
7.14B Compare the results of uniform or diverse offspring from sexual reproduction or asexual reproduction.
Supporting Standard
7.14C Recognize that inherited traits of individuals are governed in the genetic material found in the genes within
chromosomes in the nucleus.
Supporting Standard
Scientific Process TEKS
7.2
Scientific investigation and reasoning. The student uses scientific inquiry methods during laboratory and field
investigations. The student is expected to:
7.2D Construct tables and graphs, using repeated trials and means, to organize data and identify patterns.
7.2E Analyze data to formulate reasonable explanations, communicate valid conclusions supported by the data, and
predict trends.
7.3
Scientific investigation and reasoning. The student uses critical thinking, scientific reasoning, and problem solving to
make informed decisions and knows the contributions of relevant scientists. The student is expected to:
7.3A In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical
reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those
scientific explanations, so as to encourage critical thinking by the student.
7.3B Use models to represent aspects of the natural world such as human body systems and plant and animal cells.
7.3C Identify advantages and limitations of models such as size, scale, properties, and materials.
7.3D Relate the impact of research on scientific thought and society, including the history of science and contributions of
scientists as related to the content.
7.4
Scientific investigation and reasoning. The student knows how to use a variety of tools and safety equipment to conduct
science inquiry. The student is expected to:
7.4A Use appropriate tools to collect, record, and analyze information, including life science models, hand lens, stereoscopes, microscopes, beakers,
Petri dishes, microscope slides, graduated cylinders, test tubes, meter sticks, metric rulers, metric tape measures, timing devices, hot plates,
balances, thermometers, calculators, water test kits, computers, temperature and pH probes, collecting nets, insect traps, globes, digital
cameras, journals/notebooks, and other equipment as needed to teach the curriculum.
GETTING READY FOR INSTRUCTION
Performance Indicators
Grade 07 Science Unit 11 PI 01
Use a T-chart to compare the advantages and disadvantages of sexual and asexual reproduction. On the chart, define heredity, and describe the role of genes in passing
genetic material through generations.
Standard(s): 7.2D , 7.2E , 7.14A , 7.14B , 7.14C
ELPS ELPS.c.5B , ELPS.c.5C
Last Updated 04/24/13
page 1 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
Key Understandings
Genes determine traits.
— How do we get traits from our parents?
— How are genetic traits passed from one generation to the next?
— What forms of alleles exist?
— What is a dominant form of an allele?
— What is a recessive form of an allele?
All living things reproduce and pass traits to their offspring.
— How are the offspring of asexual reproduction and sexual reproduction alike and different?
— How is the Punnett square useful in predicting genetic combinations?
— What are some advantages and limitations of Punnett squares?
Vocabulary of Instruction
traits
gene
sexual reproduction
asexual reproduction
heredity
dominant trait
recessive trait
Punnett square
genotype
phenotype
DNA
chromosome
allele
Materials
article on Gregor Mendel (1 per student) – Optional
colored pencils
cover slips (1 per Station 3)
DNA model (1 per teacher) – Optional
locally adopted textbook, and/or other resources (various, per Station 1)
microscopes (1 per Station 3)
multi-colored yarn (2 m piece, 1 piece per teacher)
paper bags (30) (see Advance Preparation)
pink and blue paper (see Advance Preparation)
prepared yeast (see Advance Preparation, 2 mL per class, Station 3)
PTC paper (1 small piece per student)
slides (1 per Station 3)
sugar (1 mL per class, Station 3)
textbooks or campus based resources (per class)
timing device (1 per teacher)
toothpicks (1 per Station 3)
white paper
Attachments
All attachments associated with this lesson are referenced in the body of the lesson. Due to considerations for grading or student assessment,
attachments that are connected with Performance Indicators or serve as answer keys are available in the district site and are not accessible on the
public website.
Handout: ABC Traits (1 per group)
Handout: How do Genes Determine Traits? (1 per student)
Teacher Resource: How do Genes Determine Traits? KEY
Handout: Asexual Reproduction in Living Organisms (1 per student)
Teacher Resource: Asexual Reproduction in Living Organisms – Station Cards (1 per station)
Handout: Designer Baby (1 per pair of students)
Teacher Resource: Designer Baby Chromosomes (see Advance Preparation, 1 set per group)
Teacher Resource: PowerPoint: Punnett Square
Handout: Punnett Squares (1 per student)
Teacher Resource: Punnett Squares KEY
Resources
Suggested Websites:
Mitosis: The Division of Plant and Animal Cells: http://iknow.net/cell_div_education.html
Genetics Activity - Create The Kids. Exploring Nature Educational Resource: http://exploringnature.org/db/detail.php?dbID=22&detID=2289
Last Updated 04/24/13
page 2 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
"Mitosis: An Interactive Animation." Home of CELLS Alive! Web. 25 May 2011: http://www.cellsalive.com/mitosis.htm
Wildlife Fact Sheets: http://www.tpwd.state.tx.us/huntwild/wild/species/
Web Lab Directory: http://www2.edc.org/weblabs/WebLabDirectory1.html
Video on Pollination: http://www.neok12.com/Pollination.htm
Video on Fertilization in Plants: http://www.dnatube.com/video/11451/Process-of-plant-sexual-reproduction
Heredity and Traits: http://learn.genetics.utah.edu/content/begin/traits/
Genetics and DNA: http://sciencespot.net/Pages/kdzbiogen.html
Frayer Model: http://www.adlit.org/strategies/22369/
Advance Preparation
1. Prior to Day 2: Cut a piece of multicolored yarn into a 2 meter long section. If you don’t have multicolored yarn, consider marking a single color of
yarn with markers to be used as a model of genes on DNA.
2. Prior to Day 4:
Research and obtain an introductory level video on cells undergoing mitosis. You may wish to use the one at the following URL:
http://iknow.net/cell_div_education.html.
Secure student access to the computers/Internet, a textbook, and/or other resources for Explore/Explain II: Station 1 Research.
For Station 3, prepare the yeast to grow in a warm place by combining 2 mL of yeast with 1 mL of sugar and 4 mL of warm water (24–27oC) in a
Petri dish.
3. Prior to Day 5: Research and obtain a video clip showing pollination and fertilization. Students will use this information to organize notes on sexual
reproduction in their science notebooks. You may wish to use the one at the following URL: http://www.dnatube.com/video/11451/Process-of-plantsexual-reproduction.
4. Prior to Day 6: Prepare a class set of chromosomes by printing 34 copies of Handout: Designer Baby Chromosomes (17 on blue paper and 17
on pink paper). When cutting out the chromosomes, be sure to put an X and Y in blue for each male sack and an X and X in pink for each female
sack. You will discard the unused sex chromosome. Chromosomes will last longer if they are printed on cardstock and laminated. Create 15 sacks
for each gender, keeping the remaining chromosomes for replacements. On each paper bag, identify the pair number as well as a gender (See the
example below for reference.).
5. Prior to Day 7:
Arrange student access to computers/Internet and other campus based resources for research.
You may wish to download fact sheets from Texas Parks and Wildlife (http://www.tpwd.state.tx.us/huntwild/wild/species/); secure adopted textbooks
and/or have copies available for class use.
6. Prior to Day 9: Arrange for student computers/Internet access for research. Research and obtain a Punnett square simulation on the internet.
Check the website ahead of time to make sure that it is working properly. These activities will reinforce the work of Gregor Mendel Punnett squares.
All activities are may not be appropriate for this lesson. You may wish to use the one at the following URL: Genetic Web Lab website:
(http://www2.edc.org/weblabs/WebLabDirectory1.html). Alternatively, you may wish to print an article on Gregor Mendel.
7. Prepare attachment(s) as necessary.
Background Information
Prior to this lesson, in Grades 4 and 5, students learned the difference between inherited traits and learned behaviors. During this lesson, students continue to develop their
understanding that traits may be physical (e.g., hair color) or behavioral (e.g., birds nesting). Students also learn that in some organisms, all of the genes come from a single
parent (asexual reproduction), whereas in organisms that have sexes, half of the genes come from each parent (sexual reproduction). Additionally, students learn that in sexual
reproduction, a single specialized cell from a female merges with a specialized cell from a male. As the fertilized egg, carrying genetic information from each parent, multiplies to
form the complete organism with about a trillion cells, the same genetic information is copied in each cell. In asexual reproduction, the offspring are exact copies of the original
organism. After this lesson, students will apply these concepts as they explore genetic variations and adaptations.
STAAR Note: Student expectations 7.14B and 7.14C are both Supporting Standards that will be assessed on the STAAR Grade 8 Science Assessment. This is the last time that
sexual and asexual reproduction and the mechanisms for passing on inherited traits will be directly taught before the test. In addition, the content of this unit builds a foundation
for the material assessed in Reporting Category 2: Mechanisms of Genetics on the STAAR Biology Assessment.
For further information on genetics, please visit the following websites:
http://learn.genetics.utah.edu/content/begin/traits/
http://sciencespot.net/Pages/kdzbiogen.html
http://iknow.net/cell_div_education.html
Last Updated 04/24/13
page 3 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
INSTRUCTIONAL PROCEDURES
Instructional Procedures
ENGAGE – ABC Traits?
Notes for Teacher
NOTE: 1 Day = 30 minutes
Suggested Day 1
1. Ask/Say:
Materials:
What is a trait? Answers may vary.
A trait is a behavioral characteristic or physical attributes of an organism
that are expressed by genes and/or influenced by the environment.
timing device (1 per teacher)
Attachments:
2. Divide students into groups of 4–6.
Handout: ABC Traits (1 per group)
3. Distribute the Handout: ABC Traits to each group.
4. Say:
In past years, you have worked on developing an understanding of
inherited traits and learned behaviors. Right now, we are going to have a
competition to see which group remembers the most about inherited traits
and learned behaviors.
When I say begin, whoever has the paper will write an example of an
inherited trait or learned behavior in the square that corresponds with the
first letter of the word.
The examples do not have to be written in alphabetical order. (You may
write a word in box “H” first.) Also, more than one example can be written in
a box.
Once the first person has written an example of an inherited trait or
learned behavior, they will pass the paper to the next member of the team.
You are not allowed to pass the paper until you have written a word.
No talking is allowed. You may not help your group members. The
competition will continue for four minutes.
Any questions? Begin.
Instructional Notes:
Competition is a great motivator for children. Prior to the competition,
determine if there will be any reward for the team recording the most
traits.
Consider modeling an example to help students visualize the
concept of the competition.
Steps 9–11 are a review of 6.12D characteristics used to classify
organisms into Kingdoms and can be related to cell structure and
function.
STAAR Notes:
Student expectations 7.14B and 7.14C are both Supporting
Standards that will be assessed on the STAAR Grade 8 Science
5. Set the timer for four minutes, and monitor students as they compete.
Assessment. This is the last time that sexual and asexual
6. After the competition, instruct each team to look over their papers and circle the
examples that represent learned behaviors.
reproduction and the mechanisms for passing on inherited traits will
be directly taught before the test. In addition, the content of this unit
builds a foundation for the material assessed in Reporting Category
7. Collect the papers, and display them using a document camera. Point out several of
the inherited traits and learned behaviors. If you don’t have access to a document
camera, you can call on student volunteers to share traits.
2: Mechanisms of Genetics on the STAAR Biology Assessment.
Science Notebooks:
8. Ask:
Students draw a prokaryotic and eukaryotic cell in their science
Where did these traits come from? (Traits are inherited from the parents.)
notebooks. Students may also record examples of inherited traits
and learned behaviors as review.
9. Instruct students to draw a prokaryotic and eukaryotic cell in their science notebooks.
Students may need a review of these cells, so you may want to allow them to work on
this in partners.
10. Call on several students to identify the differences between the two cells. (Students
should know that prokaryotic cells do not have their genetic material contained in a
nucleus, but that the genetic material is still present in both types of cells.)
11. Ask:
What kingdoms of living organisms have prokaryotic cells? (Archaeabacteria
and Bacteria have prokaryotic cells.) What kingdoms belong in the Eukaryotic
domain? (Protists, Fungi, Plants, and Animals)
12. Say:
In this unit, we will focus on genetic material and how it is passed from one
generation to the next. We will learn that all living things reproduce and
pass traits to their offspring. We will also be learning what determines the
traits that are passed from one generation to the next.
EXPLORE/EXPLAIN I – How Do Genes Determine Traits?
Suggested Days 2 and 3
1. Ask:
Materials:
What determines which traits are passed from one generation to the next?
Last Updated 04/24/13
page 4 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
Accept all reasonable answers.
You know what traits are, but what is a gene? Students may offer possible
answers, but they do not have sufficient background at this time to accurately
describe genes.
2. Instruct students to look at their cell drawings from the previous day. Call on a student
to identify the difference between a prokaryotic and eukaryotic cell.
3. Hold up a 2 m piece of multi-colored yarn.
4. Say:
This yarn is a model of the amount of genetic material inside each one of a
person’s cells. The human body has 46 chromosomes, and if they were all
stretched out and connected end to end, they would be about 2 m long.
Other organisms have different amounts of chromosomes. The genetic
material is an organic compound called deoxyribonucleic acid (DNA). If
available, show students a model of DNA.
5. Ask:
multi-colored yarn (2 m piece, 1 piece per teacher)
DNA model (1 per teacher) – Optional
PTC paper (1 small piece per student)
Attachments:
Handout: How do Genes Determine Traits? (1 per
student)
Teacher Resource: How do Genes Determine
Traits? KEY
Instructional Notes:
During the PTC taste test, students who are tasters will probably
need to get a drink of water, so schedule this activity so it does not
interfere with instructional time.
The cleft chin is an example of an uncommon dominant trait. In
addition to the physical characteristics controlled by dominant
alleles, there are many traits that are not visible. One of these traits is
Where are genes located in a prokaryotic and eukaryotic cell?
Prokaryotic genetic material DNA is not bound within a nucleus. Eukaryotic genetic the ability to test a chemical called phenylthiocarbamide or PTC. If a
material, however, is contained within a nucleus within the cell and DNA is organized person has the dominant allele, PTC tastes very bitter. If the
into chromosomes.
genotype only contains the recessive alleles, the person will not
taste anything unusual.
6. Remind students that they studied organic compounds earlier in the year. Ask:
What elements does an organic compound contain (Organic compounds
contain carbon and other elements such as hydrogen, oxygen, nitrogen,
phosphorus, and sulfur. SPONCH?)
7. Inform students that a gene is a portion of DNA that contains information for a specific
trait. The segments of color on the yarn could represent genes on DNA.
8. Display the following terms on the board: gene, allele, dominant, and recessive.
If you have additional time, consider instructing students to create
Frayer Model diagrams for the terms from the activity.
Misconception:
Students may think that traits due to dominant alleles
are the most common in a population.
9. Project the following paragraph, and ask students to record important facts in their
science notebooks as someone reads them aloud.
Within the nucleus, genes occur in pairs. A gene is a segment of DNA
located on each chromosome. Each gene has a particular form. An allele is
a form of a gene. An allele can either be dominant or recessive. If a
dominant allele of a gene is present, the dominant trait will appear in an
organism. A capital letter is used to represent a dominant allele. In order
for a recessive trait to appear, both alleles of a gene must be recessive. A
lower case letter is used to represent a recessive allele.
10. Ask students to share their important facts with a partner.
STAAR Note:
This is the first time students have been introduced to concepts
relating to genetic material.
Check For Understanding:
Allowing students to create their own operational definitions for
academic vocabulary can assist in developing background. These
terms are introductory for Grade 7, so additional practice with the
terms may be in order.
11. After completing the activity, facilitate a discussion on the following questions. Illustrate
examples so students will have a visual image to assist with understanding the concept.
Science Notebooks:
What forms of alleles exist? There are two forms of a gene: a dominate allele
Students define the following terms in their science notebooks:
and a recessive allele.
gene, allele, dominant, recessive, genotype, and phenotype.
What is a dominant form an allele? The dominant form of an allele has
information for the dominant trait that is expressed. If the dominant allele is present
in the gene pair, the organism will show the dominant phenotype.
What is the recessive form of an allele? The recessive form of an allele has
information for the recessive trait that is expressed. When both genes in the pair are
recessive, the organism expresses the recessive phenotype.
12. Instruct students to record the following terms in their science notebooks: gene, allele,
dominant, and recessive.
13. Instruct students to work with a partner to define the terms in their own words. Circulate
among students to assist as necessary.
14. Ask students to share their definitions with another partner group. Allow students to
revise their definitions as needed.
15. Ask students to share their definitions with the entire class. Correct any misconceptions
as necessary.
Last Updated 04/24/13
page 5 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
16. Distribute the Handout: How do Genes Determine Traits? to each student.
17. Co-construct Part 1 with students: Check for understanding. Make sure that students
use different forms of the same letter for each trait. Point out examples of each trait.
18. Instruct students to complete Parts 2–3: Check for understanding.
19. Illustrate examples so students will have a visual image to assist with understanding the
concept.
20. Distribute a small piece of PTC paper to each student. Instruct students to place the
paper in their mouth to determine whether or not they taste the harmless chemicals on
the paper.
21. Ensure that students understand that if a person has the dominant allele, PTC tastes
very bitter. If the genotype only contains the recessive alleles, the person will not taste
anything unusual.
22. Repeat steps 10–13 above for the terms genotype and phenotype.
23. If you have additional time, consider instructing students to create Frayer Model
diagrams for the above terms. Students may need additional practice with the terms
from today’s activity as they are introductory for Grade 7.
EXPLORE/EXPLAIN II – How are Genes Passed to New Generations? Asexual Reproduction
1. Say/Ask:
Suggested Days 4 and 5
Materials:
Today, we will learn how living organisms reproduce and pass traits to their
offspring.
What are the two modes of reproduction: (Sexual and asexual reproduction)
We will begin studying asexual reproduction.
2. Instruct students to write the word asexual reproduction in their science notebooks. Ask
students to consider the parts of the word.
3. Say:
The prefix a­ means without; the root word “sexual” implies the union of an
egg and sperm cells (two parents).
locally adopted textbook, and/or other resources
(various, per Station 1)
microscopes (1 per Station 3)
slides (1 per Station 3)
cover slips (1 per Station 3)
toothpicks (1 per Station 3)
prepared yeast (see Advance Preparation, 2 mL per
class, Station 3)
sugar (1 mL per class, Station 3)
Attachments:
4. Ask students to note this information next to the term in their science notebooks.
5. Project and play a video of cells undergoing mitosis (see Advance Preparation).
Ask:
What process is being shown? (The purpose of the video is to see that asexual
reproduction can be accomplished by cell division. Students were briefly introduced
to the process of mitosis in a previous unit. They were not expected to learn it for
mastery.)
6. Inform students that there are many types of asexual reproduction including cell
division. They will be rotating through three stations to learn about the process of
asexual production. Note: To reduce group numbers, you may wish to create two sets
of stations.
7. Distribute the Handout: Asexual Reproduction in Living Organisms to each
student. Instruct students to rotate through the three stations at the teacher’s discretion
and record their answers the handout. Monitor students, and assist as needed.
8. At the end of the investigation, ask students to share reflections about how the
offspring compare to the parent in terms of traits and genetic material in asexual
reproduction. Discuss the types of asexual reproduction noted on the handout.
9. Quickly look over the student diagrams of asexual reproduction. Draw a diagram on the
board. Use a gene to show how the offspring have the same genotype as the parent.
Consider modeling with paper.
Handout: Asexual Reproduction in Living
Organisms (1 per student)
Teacher Resource: Asexual Reproduction in
Living Organisms – Station Cards (1 per station)
Instructional Notes:
Duplicate stations could be set up to accommodate large numbers
of students.
The mode of reproduction for organisms from various kingdoms
reviews Supporting Standard - 6.12D.
Misconceptions:
Students may think that sexual reproduction always
involves mating; therefore, plants cannot undergo
sexual reproduction.
Students may think that asexual reproduction is
restricted to microorganisms.
STAAR Note:
This is the first time students have been introduced to types of
reproduction.
Check For Understanding:
Ensure student understanding that asexual reproduction involves
10. Ask:
one parent and produces offspring identical to that parent. Consider
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page 6 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
What advantage would asexual reproduction offer an organism? (Asexual
reproduction does not involve finding a mate; it occurs fairly quickly.)
What disadvantages are there to asexual reproduction? (All of the offspring
have the same genetic makeup (genotype) of the parent. All of the offspring look
alike (phenotype). The offspring are uniform. There would not be biodiversity in the
population. Therefore, the chances of survival are less.)
an exit-ticket strategy to have students write down two important
ideas about asexual reproduction.
Science Notebooks:
Students define the term asexual reproduction in their science
notebooks.
11. Review the terms genotype and phenotype with students, if necessary.
12. Ask:
What would happen if the environmental conditions change and they do
not favor the trait(s) the organism had? (The species may become extinct since
all of them are genetically identical. Biodiversity increases the chances of survival.)
13. Instruct students to return to the term asexual reproduction in their science notebooks
and add a brief definition for the term that includes the following: asexual reproduction
involves one parent; produces offspring identical to that parent; and list advantages
and disadvantages of asexual reproduction.
EXPLORE/EXPLAIN III – How are Genes Passed to New Generations? Sexual Reproduction
1. Say:
Suggested Day 5 (continued)
Science Notebooks:
Today, we will continue to learn how living organisms reproduce and pass
traits to their offspring. The passing on of behavioral characteristics or
physical attributes genetically from one generation to another is known as
heredity.
Students organize notes in a table and diagram on sexual
reproduction. Students are also asked to record reflections.
2. Say:
There are two modes of reproduction: sexual and asexual. What are some
examples of asexual reproduction? (Vegetative propagation, budding, fission,
and spores are some ways organisms reproduce asexually.)
Earlier this year, you learned about the human reproductive system.
Humans use sexual reproduction to make offspring. However, many types
of organisms reproduce sexually.
3. Display a blank table similar to the following in order to assist students in taking notes
on the passage of genes to new generations through sexual reproduction. Instruct
students to draw the blank table in their science notebooks to diagram the major
components of sexual reproduction. The following is an example of a completed entry.
4. Play a video clip about pollination in plants or fertilization in animals (see Advance
Preparation).
5. Ask students to summarize the process of sexual reproduction in the table within their
science notebooks. Monitor for appropriate content.
6. Instruct students to work with a partner to discuss the notes they have recorded in their
tables. Monitor for appropriateness.
7. Project a blank table, and allow student volunteers to assist in filling completing it.
Correct any misconceptions, and discuss as needed.
8. Draw a diagram (see below) for sexual reproduction on the board. Use a set of alleles
to show the mixing of genes.
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page 7 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
9. Be sure to discuss the genotype and phenotype of the parents and offspring.
10. Instruct students to add the diagram to their science notebooks.
11. Ask students to use the notes that they have taken regarding asexual and sexual
reproduction to reflect on the following question in their science notebooks? After
allowing time for reflection, ask students to share out specific differences between the
two modes of reproduction.
How are the offspring of asexual reproduction and sexual reproduction
alike and different? In asexual reproduction, genetic material is donated from one
parent and the offspring are identical. However, in sexual reproduction, genetic
material is donated from two parents and the offspring have more genetic variation.
Asexual and sexual reproduction are alike in the following ways: both involve at least
one parent, both produce offspring, and both offspring are able to reproduce
themselves and are of the same species.
EXPLORE/EXPLAIN IV – Designer Babies
Suggested Day 6
1. Divide students into pairs for the following activity. Distribute a copy of the Handout:
Designer Baby to each pair.
2. Ask students to read the directions, and answer any questions they may have.
3. For each pair of students, distribute the chromosome sacks; a female sack to one
student and a male sack to the other (see Advance Preparation).
4. Instruct students to empty the sack onto the desk.
5. Say:
Materials:
paper bags (30) (see Advance Preparation)
pink and blue paper (see Advance Preparation)
white paper
colored pencils
Attachments:
Place the chromosomes face down, and count them to make sure that there
are 14. if you are missing any, double check in your sack before you raise
your hand to get a replacement.
The chromosomes on your desk represent the chromosomes in one cell of
your body. Humans have 46 chromosomes, and this model is limited by the
space on your desks. Therefore, we are working with less.
In order for reproduction to occur, the chromosome number must be
reduced by half. Egg and sperm cells only have half the number of
chromosomes. Otherwise, the offspring would have double the number of
chromosomes. This process is called meiosis, and it occurs in the ovaries
of females and the testes of males.
Pair your chromosomes up by size, keeping them face down on your desks.
Once you have paired them up, pick up one chromosome from each pair
and return them to the sack. (You should each have seven chromosomes
on your desks.)
After the gametes have formed through the meiosis process, fertilization
occurs.
Pair up the remaining male and female chromosomes, and turn them over
so you can see the offspring’s alleles.
Handout: Designer Baby (1 per pair of students)
Teacher Resource: Designer Baby Chromosomes
(see Advance Preparation, 1 set per group)
Instructional Notes:
Meiosis is only mentioned as background information. Students are
not expected to master mitosis or meiosis. This is intended to allow
students to connect to prior knowledge and as an introduction to
Biology concepts.
Check For Understanding:
Use student T-Charts and reflections as a formative assessment to
guide possible re-teaching.
Science Notebooks:
Students record reflections.
6. On a plain sheet of paper, instruct each pair of students to create a T-chart to record
the genotype and phenotype of the baby and sketch the facial features. Students may
wish to use color. Post the “babies” around the room.
7. Once the students have listed the genotype and phenotype, instruct them to return the
chromosomes to the correct sack.
Last Updated 04/24/13
page 8 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
8. Collect the sacks for reuse.
9. At the end of class, instruct students to observe the offspring with their partners and
then reflect individually in their notebooks about the variety of phenotypes that the
babies show.
Ask:
How do genetic combinations affect what an organism will look like? There
are three possible genetic combinations for a single gene trait (TT, Tt, or tt). If the
genetic combination includes a dominant allele, the organism will exhibit the
dominant trait.
ELABORATE I – Exploring Texas Species
Suggested Day 7
1. Instruct students to use the internet and/or campus based resources to research at
least five Texas species (see Advance Preparation). Optional factsheets are available
from Texas Parks and Wildlife: Website: "Wildlife Fact Sheets." Texas Parks & Wildlife
Department. http://www.tpwd.state.tx.us/huntwild/wild/species/
2. Students are primarily determining the reproductive strategy of the species, but this is
another opportunity to review food chains and biodiversity.
Materials:
locally adopted textbook, and/or other resources (per
class)
3. Using their science notebooks, instruct students to summarize their research in terms of
Science Notebooks:
how each species reproduces. Students should also describe the advantages and
Students summarize their research including the reproduction
disadvantages of each mode of reproduction.
process for each species including the advantages and
disadvantages of each mode of reproduction.
EXPLORE/EXPLAIN V – Punnett Squares
Suggested Day 8
1. Say:
Attachments:
Scientists use a model called a Punnett square to predict the outcome of a
particular combination of parent traits. They predict the potential
genotypes of the offspring of two parents with known genotypes.
2. Project the PowerPoint: Punnett Square.
Teacher Resource: PowerPoint: Punnett Square
Handout: Punnett Squares (1 per student)
Teacher Resource: Punnett Squares KEY
Instructional Note:
3. Demonstrate the steps of working through a Punnett square on a whiteboard or other
display. Demonstrate another square, and instruct students to record the steps in their
science notebooks.
4. Be sure to emphasize that the parents can contribute only one allele to the offspring.
5. Instruct students to complete the Handout: Punnett Squares (both the Punnett
Squares and Punnett Squares Practice pages). Monitor students, and assist them as
needed. Consider co-constructing the first one together or allow students to work in
partners on the first one.
Punnett Squares are included as a model in this lesson to assist
students in developing understanding of genetic combinations.
Science Notebooks:
Students record the steps for using a Punnett square in their
notebooks.
6. At the end of class,
Ask:
How is a Punnett square useful in predicting genetic combinations? Punnett
squares show the probability of an offspring inheriting a certain genotype.
What are the possible genetic combinations inherited from the parents?
There are three possible genotypes: both alleles/dominant; one dominant and one
recessive allele; or two recessive alleles.
What are some limitations and advantages of using a Punnett square model
to predict an offspring’s phenotype? Answers may vary
ELABORATE II – Gregor Mendel’s Work
Suggested Day 9
1. These activities reinforce the work of Gregor Mendel Punnett squares.
2. Provide a Punnett Square simulation for students to use (see Advance Preparation).
You may wish to use the one at the following URL: Genetics Web Lab Directory.
http://www2.edc.org/weblabs/WebLabDirectory1.html
Materials:
textbooks or campus based resources (per class)
article on Gregor Mendel (1 per student) – Optional
3. Optional- Group students (jigsaw grouping), or allow students to work individually.
Distribute an article about Gregor Mendel’s work to each student.
4. If using the Genetics Web Lab Directory listed above, instruct students to work on the
activity titled “Mendel’s Peas.”
Check For Understanding:
The Punnett Squares handout is an opportunity to check for
understanding.
5. If students complete the activity, you may wish to instruct them watch various genetics
videos. You may wish to use the one at the following URL:
http://www.neok12.com/Genetics.htm. You may wish to instruct students to record notes Instructional Notes:
Last Updated 04/24/13
page 9 of 25 Grade 7
Science
Unit: 11
Lesson: 01
Suggested Duration: 10 days
This activity will give students an understanding of the difficulty of
about each in their notebooks.
6. At the end of the class period, instruct students to summarize the work that Mendel
accomplished in their science notebooks.
Gregor Mendel’s work. It will also reinforce the idea of dominant and
recessive traits.
Optional: Jigsaw grouping strategies are helpful in engaging
students in reading and comprehending expository text.
Printout articles of Gregor Mendel’s work. and allow students to
complete the reading by conducting the jigsaw grouping strategies.
Consider highlighting important notes on the Article for ELL students
and others needing reading assistance.
Science Notebooks:
Students summarize Mendel’s accomplishments in their science
notebooks. Additionally, they may record notes from genetics videos.
EVALUATE – Performance Indicator
Suggested Day 10
Grade 07 Science Unit 11 PI 01
Use a T-chart to compare the advantages and disadvantages of sexual and asexual reproduction. On
the chart, define heredity, and describe the role of genes in passing genetic material through
generations.
Instructional Notes:
Inform students that they should INCLUDE the following in their Tcharts about Asexual and Sexual Reproduction: uniform or diverse
offspring and location of genetic material.
Standard(s): 7.2D , 7.2E , 7.14A , 7.14B , 7.14C
ELPS ELPS.c.5B , ELPS.c.5C
Consider setting clear expectations before allowing students to
complete the Performance Indicator. Some students may benefit
from a checklist.
1. Project the Performance Indicator on the board.
2. Share the Performance Indicator rubric or your expectations with students prior to
students beginning the assessment.
3. Answer any questions students may have regarding the assessment. Some students
may benefit from an actual model to assist them in building their T-chart.
4. Instruct students to draw a T­chart on their paper. Label the left side “Asexual
Reproduction” and the right side “Sexual Reproduction.” Under each column, describe
the advantages and disadvantages of each mode of reproduction. Remind students to
use genes in describing the two modes of reproduction and the role of genes in
passing genetic material through generations.
5. Instruct students to refer to their science notebook to assist them in the construction of
the T-chart.
Last Updated 04/24/13
page 10 of 25 Grade 7
Science
Unit: 11 Lesson: 01
ABC Traits
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
XYZ
©2012, TESCCC
01/21/13
page 1 of 1
Grade 7
Science
Unit: 11 Lesson: 01
How Do Genes Determine Traits?
Genes determine traits. An allele is a form of a gene. Each gene occurs in pairs. Each gene may
occur in one of two forms, either dominant or recessive alleles. Complete the following to practice,
understanding how scientists work with alleles. Most traits are the result of several genes, but we will
practice with some that are thought to be controlled by a single gene.
Part 1: Symbolizing Alleles
In the table below, several traits are listed. The two forms of the gene are listed. Scientists use two
forms of the same letter to represent the two alleles. A dominant allele is represented by a capital
letter. A recessive allele is represented by a lower case letter. They usually write the first letter from
the dominant allele and then the recessive allele.
Complete the table:
Trait
Handedness
Hair line
Ear lobes
Hand folding
Chin features
Toes
PTC
Dominant Allele
Right handed
Widow’s peak
Free or unattached
Left thumb on top
Cleft chin
Second toe longer than
big toe
Can taste PTC
Symbol
R
Recessive Allele
Left handed
Straight hairline
Attached
Right thumb on top
No cleft
Second toe not longer than big
toe
Can’t taste PTC
Symbol
r
Part 2: Determining the Phenotype
Genes come in pairs. There are three possible combinations (genotype) of alleles in each pair. If a
dominant allele is present, the dominant trait will appear in an organism. In order for a recessive trait
to be expressed, both alleles of a gene pair must be recessive.
In the table below, identify the expression of the gene, or how the gene is shown, in the organism.
The expression of a gene is called a phenotype. The genotype is the possible combinations of
alleles in a gene.
Genotype (combination)
RR
Ww
FF
cc
Tt
rr
©2012, TESCCC
Phenotype (expression of gene)
The person will be right handed.
01/21/13
page 1 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Part 3: Determining the Genotype
The genotype refers to the alleles in the gene pair. There are three possible combinations. If an
organism expresses a dominant trait, there are two possible genotypes.
Fill in the table below with the possible genotypes for each phenotype.
Genotype (combination)
WW or Ww
Phenotype (expression of gene)
A person with a widow’s peak
A person with a longer second toe
A person with attached ear lobes
A left handed person
A person whose left thumb is on top when they fold their hands
A person with no cleft on their chin
There are many other traits in living organisms. Gregor Mendel (the father of genetics) conducted
experiments on the traits of pea plants.
Every organism has traits that are controlled by their genes. Some traits are controlled by just one
gene pair. However, there are many traits that are controlled by more than one pair of genes (e.g.,
eye color and blood type).
©2012, TESCCC
01/21/13
page 2 of 2
Grade 7
Science
Unit: 11 Lesson: 01
How Do Genes Determine Traits? KEY
Genes determine traits. An allele is a form of a gene. Each gene occurs in pairs. Each gene may
occur in one of two forms, either dominant or recessive alleles. Complete the following to practice,
understanding how scientists work with alleles. Most traits are the result of several genes, but we will
practice with some that are thought to be controlled by a single gene.
Part 1: Symbolizing Alleles
In the table below, several traits are listed. The two forms of the gene are listed. Scientists use two
forms of the same letter to represent the two alleles. A dominant allele is represented by a capital
letter. A recessive allele is represented by a lower case letter. They usually write the first letter from
the dominant allele and then the recessive allele.
Complete the table:
Trait
Handedness
Hair line
Ear lobes
Hand folding
Chin features
Toes
Dominant Allele
Symbol
Recessive Allele
Symbol
Right handed
R
Left handed
r
Widow’s peak
Straight hairline
W
w
Free or unattached
Attached
F
f
Left thumb on top
Right thumb on top
L
l
Cleft chin
No cleft
C
c
Second toe longer than
Second toe not longer than big
S
s
big toe
toe
PTC
Can taste PTC
Can’t taste PTC
T
t
 The letter used is not as important as the form of the same letter being used. If a student
used a T for the toe, it is acceptable as long as they use a t for the recessive allele.
Part 2: Determining the Phenotype
Genes come in pairs. There are three possible combinations (genotype) of alleles in each pair.
If a dominant allele is present the dominant trait will appear in an organism. In order for a recessive
trait to be expressed, both alleles of a gene pair must be recessive.
In the table below, identify the expression of the gene, or how the gene is shown, in the organism.
The expression of a gene is called a phenotype. The genotype is the possible combinations of
alleles in a gene.
Genotype
RR
Ww
FF
cc
Tt
rr
©2012, TESCCC
Phenotype
The person will be right handed.
The person will have a widow’s peak hairline.
The person will have unattached ear lobes.
The person will not have a cleft chin.
The person will be able to taste PTC paper.
The person will be left handed.
01/21/13
page 1 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Part 3: Determining the Genotype
The genotype refers to the alleles in the gene pair. There are three possible combinations. If an
organism expresses a dominant trait, there are two possible genotypes.
Fill in the table below with the possible genotypes for each phenotype.
Genotype
WW or Ww
SS or Ss
ff
rr
LL or Ll
cc
Phenotype
A person with a widow’s peak
A person with a longer second toe
A person with attached ear lobes
A left handed person
A person whose left thumb is on top when they fold their hand
A person with no cleft on their chin
There are many other traits in living organisms. Gregor Mendel (the father of genetics) conducted
experiments on the traits of pea plants.
Every organism has traits that are controlled by their genes. Some traits are controlled by just one
gene pair. However, there are many traits that are controlled by more than one pair of genes (e.g.,
eye color and blood type).
©2012, TESCCC
01/21/13
page 2 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Asexual Reproduction in Living Organisms
Station 1: In order to review the domains and kingdoms of living organisms, fill in the chart below.
Leave the examples blank until you have rotated through each station. You may find examples while
conducting the investigation.
©2012, TESCCC
01/21/13
page 1 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Station 2 : Types of Asexual Reproduction
Add the organisms listed on the chart to the proper list of examples above.
What are the three main types of asexual reproduction?
What do all three types of asexual reproduction have in common with each other?
How will the offspring compare to the parent in terms of traits and genetic material?
Diagram the process of asexual reproduction.
Station 3: Asexual Reproduction in Yeast
Draw the yeast budding.
High Power
©2012, TESCCC
01/21/13
page 2 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Asexual Reproduction in Living Organisms
Station 1
Use the Internet, textbook, and/or other reference material to identify the
domains and kingdoms of living organisms.
Complete the Part 1 chart on your handout.
©2012, TESCCC
01/21/13
page 1 of 3
Grade 7
Science
Unit: 11 Lesson: 01
Asexual Reproduction in Living Organisms
Station 2
Read the following table:
Organism
Type of Asexual
Reproduction
Description
Bacteria
Fission
Bacteria are unicellular prokaryotes that
reproduce by splitting into two new cells.
Spider plant
Vegetative
propagation
Spider plants produce new plants from roots or
runners. The root or runner can be placed in
water or soil to produce another plant. This
process is sometimes referred to as “cuttings”.
Cyanobacteria
Fission
Cyanobacteria is a unicellular prokaryote that
reproduces by splitting into two new cells.
Protists
Fission
Protists are unicellular, eukaryotic organisms that
reproduce by splitting in two.
Hydra
Budding
Hydra reproduces through cell division to form a
bud that is an identical copy of its single parent.
The bud eventually separates from the parent and
becomes independent.
Strawberries
Vegetative
propagation
Strawberries reproduce from runners or roots.
Strawberries also reproduce sexually.
Fungi
Spores
Mold and mushrooms asexually produce spores,
which are packets of cells that leave the parent
and grow in a new location.
Answer the questions on your handout.
©2012, TESCCC
01/21/13
page 2 of 3
Grade 7
Science
Unit: 11 Lesson: 01
Asexual Reproduction in Living Organisms
Station 3
Materials:

microscope

prepared yeast (in Petri dish)

microscope slide

cover slip

toothpick

water

paper towels
Procedure:
1. Smear a sample of yeast on a microscope slide with a toothpick.
2. Cover with a cover slip.
3. Use the microscope to focus properly on high power.
4. Record illustrations of the yeast budding.
5. Rinse the slide and cover slip. Dry thoroughly.
©2012, TESCCC
01/21/13
page 3 of 3
Grade 7
Science
Unit: 11 Lesson: 01
Designer Baby
Allele from
Mother
Allele from
Father
Genotype of
Baby
Phenotype of Baby
Widow’s Peak
Hair Color
Ear Lobes
Dimples
Curly Hair
Freckles
Gender
Draw the traits onto the outline below.
©2012, TESCCC
01/21/13
page 1 of 1
Grade 7
Science
Unit: 11 Lesson: 01
Designer Baby Chromosomes
No
Red Hair
No
Widow’s
Peak
Widow’s
Peak
Make 34 copies - 17 blue and 17 pink. Cut them apart, and put them into paper sacks marked male and female.
d D C c
No Dimples
©2012, TESCCC
Dimples
Curly
Hair
01/21/13
Straight
Hair
No
Freckles
Free Ear
Lobes
Freckles
Attached
Ear Lobes
Red Hair
e E
page 1 of 1
Grade 7
Science
Unit: 11 Lesson: 01
Punnett Squares
1. Draw a tic-tac-toe square on your paper.
2. Label the top left corner as male ♂/ female♀
♀
♂
(Although it does not matter which gender is where, it makes it easier
to determine any errors in the process.)
♂
♀
3. Identify the male genotype, and place one allele in each
box across the top.
T
t
T
t
4. Identify the female genotype, and write the alleles
down the left side.
♂
T
T
TT
t
Tt
♀
t
Tt
5. Determine the results of the cross.
tt
6. Record the possible genotypes and phenotypes of the offspring.
Genotype:
1 TT
1 Tt
1 tt
Phenotype: 3 Tall/1 short
©2012, TESCCC
01/21/13
page 1 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Punnett Squares Practice
Key
Dominant Trait
Recessive Trait
T- Tongue roller
t- Non-roller
F- Free ear lobes
f- Attached lobes
D- Dimples
d- No dimples
Q- Curly hair
q- Straight hair
1. A cross between a TT ♂ tongue roller and a Tt ♀ tongue roller.
Male Alleles _____ or _____
♀
♂
Female Alleles _____ or _____
Possible Offspring - Genotype: ____________________
____________________
Phenotype: ____________________
2. A cross between a male with attached ear lobes and a female who shows the recessive trait for ear lobes.
(Draw the Punnett square, and fill it in. Remember to include the offspring’s genotype and phenotype.)
3. A cross between a dimpled Dd ♂ and a Dd ♀.
4. A cross between a Qq male and a QQ female.
©2012, TESCCC
01/21/13
page 2 of 2
Grade 7
Science
Unit: 11 Lesson: 01
Punnett Squares KEY
Key
Dominant Trait
Recessive Trait
T- Tongue roller
t- Non-roller
F- Free ear lobes
f- Attached lobes
D- Dimples
d- No dimples
Q- Curly hair
q- Straight hair
1. A cross between a TT ♂ tongue roller and a Tt ♀ tongue roller.
Male Alleles T or T
♂
T
T
TT
t
Tt
♀
Female Alleles T or t
Possible Offspring - Genotype: 2 TT and 2 Tt
Phenotype: 4 tongue rollers
T
TT
Tt
2. A cross between a male with attached ear lobes and a female who shows the recessive trait for ear lobes.
(Draw the Punnett Square and fill it in. Remember to include the offspring’s genotype and phenotype.)
All four offspring possibilities will have attached ear lobes and have the
♀
ff genotype.
3. A cross between a dimpled Dd ♂ and a Dd ♀.
♀
The genotypes of the possible offspring will be:
♂
D
d
D
DD
Dd
d
Dd
♂
f
f
f
ff
ff
f
ff
ff
1 DD, 2 Dd, and 1 dd.
The phenotypes will be three dimpled and one
non-dimpled.
dd
♀
4. A cross between a Qq male and a QQ female.
There are two possible genotypes - 2 QQ and 2 Qq.
♂
Q
q
Q
QQ
Qq
Q
QQ
Qq
All offspring will have curly hair.
©2012, TESCCC
01/21/13
page 1 of 1