Download File - Ms. Mathiot`s 7th Grade Science Class

Your Name_________________________________________
Period_________
Teacher_________________________
Today’s Date___________________________
Genetics
This packet will be practice in the
following 7th Grade Standards:
 I can distinguish between inherited and learned traits
 I can explain how inherited traits are passed from generation to generation
 I can describe the relationships among phenotype, genotype, chromosomes, and
genes.
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Genetics Unit Vocabulary
Unit Vocabulary List – Keep track of all of the unit’s vocabulary words as we go. Define the
ones already on the chart, and add any other ones that seem tricky
Term
DNA
Allele
Gene
Chromosome
Dominant
Recessive
Phenotype
Genotype
Heterozygous
Homozygous
Definition
Sketch
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An Inventory of My Traits – Survey
A trait is ___________________________________________________________________________________________________
______________________________________________________________________________________________________________
Some of our traits are determined by our experiences and environment. Many of our traits are
determined by genes, sections of DNA that code for proteins, which control traits. There are
millions of different genes and billions of different combinations, which is why we’re all unique!
Below is a list of several common genetic traits. Take the survey to find out
what combination you have!
1. I have detached earlobes
Yes
No
2. I can roll my tongue
Yes
No
3. I have dimples
Yes
No
4. I like spicy foods
Yes
No
5. I am great at sports
Yes
No
6. I have a cleft chin
Yes
No
7. I clasp my hands left over right
Yes
No
8. I have a ‘widow’s peak’
Yes
No
9. I am good at Math
Yes
No
10. I have freckles
Yes
No
11. I can taste PTC
Yes
No
Consider the Following:
1. Do you have any of these traits in common with other people in your family? Which ones?
2. Just because you have traits in common with your family, does it always mean they were inherited on your
genes? Explain
3. Which of these traits do you think are inherited?
4. Which of these traits do you think are learned?
5. Do you think any of these traits are a combination of inherited & learned?
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Tongue Roll
a) Possible Phenotypes
b) My Phenotype
c) Alleles for this trait
d) Possible Genotypes
e) My Genotype
-Please complete the remaining for 2 more genetic traits we learned about in class.
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Intro to Genetics
Think about the things that make you who you are; physical traits such as eye color, hair
color, height, etc.; abilities such as intelligence, problem solving, strength or speed; and
personality traits such as sense of humor or kindness. Some traits are determined by your
environment, some traits are determined by your genes, while other traits are a combination
of your genes and your environment working together. Scientists are still unraveling
many of the questions about what makes us who we are, but a good starting point is an
understanding of basic genetics.
Genetics & Heredity
A gene is a piece of information about an organism that is determined by a
sequence of DNA. Genes are passed on from parent to offspring. The
passing of genes from one generation to the next is called heredity.
Genetics is the branch of science that studies genes and heredity.
DNA, and therefore genes, is found on structures called chromosomes.
Humans have 23 pairs of chromosomes for a total of 46, found
in the nucleus of body cells. Chromosomes come in pairs because
for each chromosome we inherit one from our mother and one
from our father. When we inherit chromosomes from our parents,
we inherit the genes that are on them.
It is estimated that humans have about 21,000 genes. See the table below for other organisms.
Organism Number of
Chromosomes
Fruit Fly 8
Yeast
16
Rice
24
Dog
78
Mouse
40
Human
46
Number of
Genes
13,600
6,275
46,000
25,000
23,000
21,000
Genes & Proteins
As you know, a gene is a sequence of DNA. The gene that is coded for by a stretch of DNA then
allows for a certain type of protein to be made. The protein that is made will determine the
hereditary characteristics of the organism such as blood type and hair, eye, and skin color. But
many of the proteins determined by genes simply guide the growth and development of your
cells, ensuring that the right structures are made, that cells divide properly, and the correct
chemical reactions can occur. Unfortunately, there are many examples of genes that code for
proteins that do not allow for proper cell functions, which may result in a genetic disorder such as
cystic fibrosis or higher risk for diseases such as cancer.
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Alleles
Each of your genes is actually made of 2 sets of information, because for every
gene you get a set of information from your mom and a set of information
from your dad (Remember that chromosomes come in pairs, and genes are
on chromosomes. . . so each gene is made of a pair of information) Each set of
information that makes a gene is called an allele. An allele is sometimes
defined as an alternative form of a gene. You inherit one allele for each gene
from your mom and the other allele for the gene from your dad. What you
will look like is then determined by the interaction between the two alleles
(more on that later!)
For example, the gene that determines whether or not you have a hitchhiker’s
thumb is made of a set of information from your mom and a set of information
from your dad . The alleles, or alternative gene forms, for type of thumb
would be hitchhiker thumb or straight thumb. What type of thumb do you have?
What type of thumb do your parents have? If your thumb is not the same as your
parents, how can that be? Can we know what alleles they passed on to you? To really
understand what is going on, we need to learn a little bit more.
Dominant & Recessive
Some alleles that make up a gene pair are known as dominant alleles while others are known as
recessive alleles. A dominant allele will always be expressed if it is part of the allele pair. On the
other hand, a recessive allele will be hidden by a dominant allele when they are paired up.
Recessive alleles can only be expressed if there are two recessives in the pair.
For example, a straight thumb is dominant to a hitchhiker’s thumb. To communicate information
about alleles, we use uppercase letters for dominant traits and lowercase letters for recessive traits.
*In this example T=straight thumb t=hitchhiker’s thumb.
*The possible allele combinations you could have are TT, Tt, or tt.
*Since “TT” and “Tt” both contain a dominant allele, the person would express the dominant allele and
have a straight thumb. Notice that the recessive “t” is masked by the dominant in the “Tt” combination.
*However, the “tt” does not contain a dominant allele, and therefore the recessive would be expressed.
This person would have a hitchhiker’s thumb.
Notice that a person can have information in their genes that does not show up in them! If you have
a straight thumb, you could be “carrying” hitchhiker’s thumb without knowing it because it doesn’t
show up in you. Some important vocabulary words to add at this point are genotype and
phenotype. Your genotype is the information that is in your genes. . .in other words the letter
combination of the 2 alleles. Genotypes are either called homozygous if the 2 alleles are the same
(TT or tt) or heterozygous if the 2 alleles are different (Tt). Your phenotype is the physical
characteristic that shows up in you. You can see your phenotype but you can’t see your genotype
Finally . . .
Dominant does not mean you are more likely to pass the dominant allele on to your offspring. No matter
what your 2 alleles are, you have a 50% chance of passing each on (but we will learn more about that later).
Dominant traits are not always more common in the population either, but students often think this is the
case. For example, extra fingers is a dominant trait but it is quite rare.
We will also learn about some cases where there can be 2 dominant alleles that pair up in a circumstance
called co-dominance and cases where the 2 alleles mix together in a circumstance called incomplete
dominance. There is still a lot to learn about Genetics!
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Intro to Genetics:
Topic
Genetics &
Heredity
Genes &
Proteins
Alleles
Dominant
and
Recessive
Information I Know
Information I Learned
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Notes-Genes & Alleles
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Extension: Is Dominant More Common?
1) What to do: Choose 3 traits from the traits we just examined in the
‘Inventory of My Genetic Traits’
-Widow’s Peak
-Tongue Roll
-One other single-gene trait of your choice (Examples: Hitchhiker’s thumb, Attached vs.
Free Earlobes, Cleft chin, Dimples)
2) Create one or more data tables to show the WHOLE CLASS’S results for
each of those 5 traits. Your data table(s) might include fractions and/or
decimals, and then a percentage calculation for each trait.
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3) Create a bar graph below to show your results. “Trait” should be on the X-axis and
“Percent” should be on the Y-axis. Please color-code the dominant trait in red and the
recessive trait in blue.
Follow-Up Questions
1) From your data, would you conclude that dominant means more common in the
population? Explain using specific data.
2) Explain 2 ways in which this investigation could be improved or changed to
explore whether dominant means more common.
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Research Challenge-Find out about dominant traits that are
uncommon. Write about them on the back page of the packet or present your findings with the class
Dominant & Recessive
Dominant
Is
Is Not
Examples
a)
b)
c)
Is
Recessive
Examples
a)
b)
c)
Is Not
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Notes- Meiosis
1) The purpose of meiosis is :
2) Like mitosis, meiosis is a process of ____________________________________________________. However,
unlike mitosis, meiosis begins with a cell with ______________________________ and ends with four cells
each with ___________________________________________
4) Meiosis and sexual reproduction create diversity when ________________________________________________
____________________________________ and when ___________________________________________________________
How It Looks
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Probability
Prediction: What are the chances each time you flip a coin that you get
heads? What are the chances you get tails?
Try It:
Flip a coin once, twice, then ten times.
-Did your prediction work out?
-Why or why not?
-What if you flip the coin more than ten times?
(Please pick up a set of instructions for the rest of the assignment)
Data Table:
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Notes-Punnett Squares
pg. 13
-A punnett square is:
-The _____________________________________________________________must be
known.
-Punnett Squares predict_______________________, not ___________________
Examples:
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Punnett Square Practice Problems
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Incomplete & Co-dominance
Barnyard Genetics Drawing:
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Video or Article Notes:
In this unit, we may watch some video clips or read some articles about genetics topics such as DNA
testing, genetically modified food, and genetic engineering. Please save this page for notes.
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Fun Stuff!
Genetics Word Search
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Ultra-Super-Challenge Punnett Square!
Truffula Trees
A green-leaved truffula tree is crossed with a striped-leaved truffula tree. All of the
offspring are green-leaved. Make a punnett square showing the potential genotypes
and phenotypes you could get if you crossed two of these OFFSPRING together!