Download Genetics

FISH
Genetics
PART
A
Teacher’s Instructions:
1) This is the Part A of a three-part (A, B and C) project about fish genetics. Even If you do
not wish to complete the entire project, you may still use Part A as a stand-alone
activity.
2) Activate students’ prior knowledge by asking them the following questions:
“Have you ever been told that you...
A) have your mother’s/father’s eyes/nose?
B) look like your mother/father?
C) are tall like your grandmother/grandfather?
“Do you think fish look like their parents?”
3) Explain to students that they will complete a project (if you have decided to do so)
about Fish Genetics. This project is separated into Parts A, B and C. This hand out
contains the project details for Part A. Below is a summary of the entire project. Details
for Parts B and C can be found in PartB.pdf and PartC.pdf respectively
(visit http://www.gov.mb.ca/conservation/sustain/12.html).
Part A: Genes, Peas!
Students will learn about Mendel’s principles and genetic terminology.
Part B: Square Dance (grab your partner!)
Students will learn how to use Punnett squares and pedigree charts to
illustrate inheritance and solve problems.
Part C: Create a Fish
Students will use the knowledge they gained from parts A and B to create a
fish (an offspring fish from two parent fish).
4) To complete Part A, hand out pages 2 to 12 to each student.
5) Students will read the background information on pages 2 to 6.
6) Students will use the background information and references listed on page 7 to answer
the questions on pages 7 to 12.
7) Assessment: you may collect the question sheets or correct them in class. Answer
keys are provided on pages 13 to 15. You may also wish to display the genetics
time lines around the classroom.
white sucker
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FISH
Genetics
PART
A
PART A: Genes, Peas!
Objectives:
1) To be able to outline Mendel’s principles of inheritance, describing their importance to
the understanding of heredity.
2) To explain what is meant by the terms heterozygous and homozygous.
3) To distinguish between genotype and phenotype and use these terms appropriately
when discussing the outcomes of genetic crosses.
Tasks:
1) Read pages 2 to 6.
2) Complete the questions on pages 7 to 12 (use the resources listed on page 7).
Key Terms:
- allele: one of two (or more) alternative forms of a gene that give rise to alternative
characteristics for a specific hereditary trait (see diagram below).
- chromosome: a strand of DNA that carries genes (the genetic information of an organism).
Chromosomes are capable of replicating themselves with each cell division
(see diagram below).
- gene: a hereditary unit (made up of DNA) that occupies a specific location on a
chromosome. A gene determines a particular characteristic in an organism
(see diagram below).
- genetics: a branch of biology that deals with heredity and variation of organisms.
- genotype: the genetic makeup of an organism or a group of organisms (the actual alleles).
- heredity: the transmission of characteristics from parent to offspring.
- heterozygous: having 2 different alleles for a trait (e.g. Rr).
- hybrid: heterozygous or mixed.
- homozygous: having 2 identical alleles for a trait (e.g. RR or rr).
- phenotype: the expression of characteristics for a specific trait, the observable physical
or biochemical characteristics of an organism.
- purebred: homozygous.
Cell
Gene
DNA
Nucleus
R
r
Alleles
Chromosomes
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FISH
Genetics
PART
A
Background:
Gregor Mendel was born in 1822. His parents farmed but were very poor; they could
not afford to send Gregor to university. So, in 1843, Gregor decided to join a monastery.
Monastery life afforded Mendel time for his two passions: studying and gardening. Thus,
Mendel began to experiment with plant breeding.
First, Mendel studied pea plants and their characteristics. He noticed several
characteristics of traits in pea plants:
1) seed colour: yellow or green,
2) seed shape: round or wrinkled,
3) flower colour: white or coloured,
4) form of ripe pod: smooth or wrinkled,
5) colour of unripe pods: green or yellow,
6) position of flowers: side or end,
7) length of stem: long or short.
For his first experiment, he decided to crossbreed pea plants with round and wrinkled
seeds. He used purebred plants as “parent” plants. Mendel knew that the plants were
purebred because he grew them over several generations and they always produced
offspring with the same characteristic for the trait of seed shape. After crossing 2 purebred
plants and observing the offspring (seeds), he noticed that all of the seeds were round he could not find one wrinkled seed!
Purebred
Round
Parents
Offspring
Purebred
Wrinkled
Round
first generation
He noticed that one of the characteristics (round) appeared and the other characteristic (wrinkled) disappeared. He performed experiments with characteristics of other traits
and observed the same results. For example, when tall and short plants were crossed, all
the offspring were tall. Mendel used the term “dominant” for the characteristic that
appeared and the term “recessive” for the characteristic that did not appear. For pea
plants, round seeds and tall plants (long stem) are dominant characteristics while wrinkled
seeds and short plants (short stem) are recessive characteristics for stem length and seed
shape traits.
x
=
3
FISH
Genetics
PART
A
These results sparked Mendel’s curiosity. He decided to perform another experiment
which involved crossbreeding the plants from the first generation to see which characteristic would appear in the second generation offspring. Mendel discovered that the
second generation offspring had both round AND wrinkled seeds! The recessive characteristic had somehow reappeared. Mendel noticed that the ratio of round to wrinkled
seeds was 3:1.
Parents
Offspring
First Generation
Round
First Generation
Round
Round : Wrinkled (3:1)
second generation
Mendel performed this experiment again with the second generation offspring and
obtained the following results.
Parents
Offspring
Parents
Offspring
Second Generation
Wrinkled
Second Generation
Wrinkled
All Wrinkled
Second Generation
Round
third generation
Second Generation
Round
Round : Wrinkled (3:1)
third generation
Mendel continued to conduct similar experiments. During each experiment, he chose
only one trait to study. He collected data for thousands of pea plants. During the winter
he analyzed the data and made some conclusions:
- Since each trait can be expressed in different ways, there
must be two factors (alleles) that affect the expression of the
characteristics for that trait.
- One of the alleles is dominant (appears in heterozygotes/hybrids)
and one allele is recessive (is ‘masked’ or ‘hidden’ in heterozygotes/
hybrids)
- Each individual contains two alleles (either both dominant, both
recessive, or one of each) for each trait.
- The alleles must come from the parents. Offspring receive one
allele from each parent.
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FISH
Genetics
PART
A
Mendel also diagramed the results. Note: R = round (dominant), r = wrinkled (recessive).
Parents
RR rr
Rr Rr Rr Rr
Rr x Rr
RR Rr Rr rr
Purebred Round
RR
First Generation
Offspring
Parents
X
X
Purebred Wrinkled
rr
All Round
Rr
First Generation Round X First Generation Round
Rr
X
Rr
Second Generation
Offspring
Round : Wrinkled (3:1)
RR Rr rR : rr
Finally, Mendel formulated 3 principles of heredity:
1) Principle of Segregation: each trait is made up of two factors.
Each parent provides one factor of a characteristic for a trait.
Trait = shape of seed
Factors = round and wrinkled
2) Principle of Dominance: in a heterozygous/hybrid pairing, the allele that
is expressed in the phenotype is dominant. The allele that is not
expressed is recessive.
Trait = shape of seed
Expressed = round or wrinkled
Dominant = round
Recessive = wrinkled
3) Principle of Independent Assortment: each trait is determined separately
from other traits because chromosomes sort independently.
The shape of the seed (a trait) does not affect
the colour of the seed (another trait).
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FISH
Genetics
PART
A
Today we use terms such as genotype, phenotype, homozygous and heterozygous
when discussing genetics.
Genotype refers to the genes inherited by an offspring from its parents. For example,
the genotype for a pea plant with round seeds could be RR. The genotype could also
be Rr (or rR). The genotype for a pea plant with wrinkled seeds would be rr.
Phenotype refers to the appearance of a trait in an offspring. For example, you may
see a pea plant that has round seeds but you would be unable to tell (by observation
alone) what the genetic makeup (genotype) of that plant would be. Since round is
dominant, it would be impossible to tell if this particular pea plant had two dominant
alleles (RR), or a dominant allele and a recessive allele (Rr). The expression of a recessive
characteristic for a trait is the only case where the phenotype can be used to determine
the genotype. For example, if a pea plant has wrinkled seeds and it is known that wrinkled
seeds is recessive, then you would know that the genotype must be rr.
SEEDS
ROUND
WRINKLED
PHENOTYPE
GENOTYPE
RR
rR
Rr
rr
A genotype that has two like alleles is called homozygous. For example, the genotype
for wrinkled seeds is homozygous because it is rr. The genotype for round seeds is
homozygous only if it is RR. If the genotype for round seeds is rR or rR, then it is called
heterozygous - meaning that the alleles are different.
HOMOZYGOUS
RR
rr
HETEROZYGOUS
Rr
rR
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FISH
Genetics
PART
A
References:
History of Genetics Timeline by Jo Ann Lane. Available at:
http://www.accessexcellence.org/AE/AEPC/WWC/1994/geneticstln.html
Genetics in Context. Available at: http://www.esp.org/timeline/
Time line of the History of Genetics. Available at:
http://www.bio.davidson.edu/people/kahales/301Genetics/timeline.html
Variation and Mendel’s Laws. Available at:
http://www.mnsu.edu/emuseum/biology/evolution/genetics/mendelsvariation.html
Mendelian Genetics. Available at:
http://www.ndsu.nodak.edu/instruct/mcclean/plsc431/mendel/mendel1.htm
white sucker
channel catfish
Questions:
Use the background information and web resources (listed above) to complete the
following questions.
1) Complete the time line on pages 8 to 10. (Fill in the blanks.)
7
1600
1650
Robert
_______
discovers
the cell.
1665
1700
GENETICS TIME LINE
1754
Pierre
_________
suggests
species
transform
over time.
1750
Overlap
8
Overlap
_____
Lamarck
publishes
Philosopie
Zoologique
1800
1824
_________
discovers
that tissue
is made
from
living cells
1831
Charles
______
sets out
on his
voyage
on the
________
1833
Robert
______
discovers
the cell
nucleus
1850
1859
Darwin publishes
_____________
_____________
_____________
_____________
_____________
______
Mendel
formulates
the principles
of heredity.
1868
______
discovers
nuclein
(DNA)
______
Waldyer
names the
chromosome
1900
1927
Hermann
________
shows that
X-rays cause
mutation
GENETICS TIME LINE
_________ and
__________
discover the
structure
of DNA
___________
1950
Overlap
9
10
1985
Alec
________
develops a
method of
DNA
fingerprinting
1987
Genetically
engineered
plants first
developed.
1989
Seven cloned
calves are
born from the
same embryo.
2000
Your predictions for the field of genetics:
2050
GENETICS TIME LINE
FISH
Genetics
PART
A
2) Complete the following definitions:
Definition:
Word or Concept
Diagram:
Heterozygous
Synonym/Example
Definition:
Word or Concept
Diagram:
Homozygous
Synonym/Example
Definition:
Word or Concept
Diagram:
Phenotype
Synonym/Example
Definition:
Word or Concept
Diagram:
Genotype
Synonym/Example
Reference: Adapted from Simons, Sandra M. Strategies for Reading Nonfiction. Copyright © 1991 by Spring Street Press.
Used by permission of the publisher.
Source: Success for All Learners: A Handbook on Differentiating Instruction: A Resource for Kindergarten to Senior 4.(p. 6.36 and 6.101)
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FISH
Genetics
PART
A
3) Match each scenario with one of Mendel’s laws (select the law that matches the scenario
the best).
In white suckers, light grey colouring of the scales
A is dominant to dark grey scales. However, it is
possible for two light grey suckers to produce an
offspring with dark grey colouring.
Principle of Segregation
B
Many traits such as spots on body, length of barbels,
and colour of skin can be observed on catfish. It is
possible to see any combination of these traits in
individual catfish.
Principle of Independent
Assortment
Principle of Dominance
In humans, hairline shape (smooth or widow’s peak)
C is coded for by a single pair of genes. A man with
a widow’s peak has several children with a woman
who also has a widow’s peak and some of the
children have a smooth hairline.
4) Complete the following chart. The two characteristics for the colour of scales trait in
sucker fish are light and dark. Light (L) is dominant and dark (l) is recessive.
GENOTYPE
PHENOTYPE
HOMOZYGOUS or HETEROZYGOUS
LL
dark scales
heterozygous
white sucker
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FISH
Genetics
PART
A
Answer Key:
1) Time line:
1665 Robert Hooke discovers the cell.
1754 Pierre Maupertuis suggests species transform over time.
1809 Lamark publishes Philosopie Zoologique.
1824 Rene Dutrochet discovers that tissue is made from living cells.
1831 Charles Darwin sets out on his voyage on the Beagle.
1833 Robert Brown discovers the cell nucleus.
1859 Darwin publishes Origin of Species by Natural Selection.
1865 Mendel formulates the principles of heredity.
1868 Freidrich Miescher discovers nuclein (DNA).
1888 Waldyer names the chromosome.
1927 Hermann Muller shows that x-rays cause mutation.
1953 Crick and Watson discover the structure of DNA.
1985 Alec Jefferie develops a method of DNA fingerprinting.
1987 Genetically engineered plants first developed.
1989 Seven cloned calves are born from the same embryo.
Predictions:
- students should make a few predictions about major events or
discoveries in the field of genetics.
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FISH
Genetics
PART
A
2) Complete the following definitions:
Definition:
- having two
different alleles
for a trait
Word or Concept
Diagram:
Heterozygous
Rr
Synonym/Example
different
Definition:
- having two
identical alleles
for a trait
Word or Concept
Diagram:
Homozygous
RR
rr
Synonym/Example
same
Definition:
- the expression of a
specific trait, the
observable expression
of a characteristic for
a specific trait in an
organism
Definition:
- the genetic
makeup of
an organism
Word or Concept
Diagram:
Phenotype
Synonym/Example
appearance
Word or Concept
Genotype
Synonym/Example
genes
Diagram:
Rr
RR
rr
Reference: Adapted from Simons, Sandra M. Strategies for Reading Nonfiction. Copyright © 1991 by Spring Street Press.
Used by permission of the publisher.
Source: Success for All Learners: A Handbook on Differentiating Instruction: A Resource for Kindergarten to Senior 4.(p. 6.36 and 6.101)
14
FISH
Genetics
PART
A
3) Match each scenario with one of Mendel’s laws (select the law that matches the scenario
the best).
A
In white suckers, light grey colouring of the scales
is dominant to dark grey scales. However, it is
possible for two light grey suckers to produce an
offspring with dark grey colouring.
C Principle of Segregation
B
Many traits such as spots on body, length of barbels,
and colour of skin can be observed on catfish. It is
possible to see any combination of these traits in
individual catfish.
B Principle of Independent
Assortment
A Principle of Dominance
In humans, hairline shape (smooth or widow’s peak)
C is coded for by a single pair of genes. A man with
a widow’s peak has several children with a woman
who also has a widow’s peak and some of the
children have a smooth hairline.
4) Complete the following chart. The two characteristics for the colour of scales trait in
sucker fish are light and dark. Light (L) is dominant and dark (l) is recessive
GENOTYPE
PHENOTYPE
HOMOZYGOUS or HETEROZYGOUS
LL
light scales
homozygous
ll
dark scales
homozygous
Ll
light scales
heterozygous
white sucker
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