Download Heredity in Rabbits

`
Activity: Heredity in Rabbits
Background Information:
Rabbits are small, furry animals with several distinct traits or characteristics, such as long back legs and
long ears. Traits are passed from parents to their off spring during reproduction. Each offspring receives
half of its genetic information or DNA from each parent.
A gene is a section of DNA that carries information for a specific trait, such as coat color. Genes come
in pairs, and one allele or form of the gene comes from each parent. The pair of alleles that carry
information for a trait are represented by two letters, called the genotype. Alleles can be dominant or
recessive. If a dominant allele is present, then the dominant trait will be seen in the offspring. A
dominate trait is represented by a capital letter. A recessive allele is only seen in the offspring if both
alleles are represented by a lowercase letter.
The phenotype is the expression of the trait or how the offspring looks. This activity investigates how
the trait of fur is passed from parent to offspring.
Allele
Genotype
Phenotype
B = black
BB
Bb
bb
Black
Black
White
b=white
Materials: pictures of black and white rabbits, 2 lunch size paper bags – one labeled Mom, the other
labeled Dad, 5 black beans and 5 white navy beans put into each bag, 2 small cups
1. Work with a partner. One person chooses the mother’s allele for color, and the other person chooses
the father’s allele for color.
2. Without looking into the bag, choose a bean for each trial. Record a capital B each time a black bean
is chosen and record a lowercase b each time a white bean is chosen by each person. Keep selecting
gene pairs for ten trials.
3. Record the two letters in the genotype column, recording the capital B first if it’s present.
4. Record the color of the offspring in the phenotype column.
`
Data Table:
Trial
Mother’s
Allele
Father’s
Allele
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Questions:
1. What genotype combinations resulted from the 10 trails?
2. What phenotypes resulted from 10 trials?
3. What phenotypes resulted from the genotype bb?
4. Does any other genotype result in white fur?
5. What genotype resulted in the phenotype of black fur?
Genotype
Phenotype
`
6. The rabbit parents shown in the diagram below are homozygous which means both alleles are the
same in their genotype. What are the genotypes of the parents?
7. If an organism has two different alleles for the same trait, it is called heterozygous. Are the four
offspring homozygous or heterozygous?
X
B
Bb
B
b
Bb
Bb
b
Bb
`
Another way to predict possible combinations of alleles in offspring is to use a Punnett Square.
Punnett Squares:
A Punnett Square is a chart used to predict the probability that certain traits will pass from parents to
offspring during reproduction. It shows the probability that each four offspring will receive a certain
combination of genes from the parents. To set up a Punnett Square, draw a large square, and divide it
into 4 square sections. Each square represents an offspring.
Allele Key
B=black
b=white
8. What are the genotypes of the rabbit offspring?
`
9. Calculate the probability of rabbit offspring for each genotype:
Example:
Probability =
Probability =
Probability =
Probability =
number of squares with AA
_______________________________________
Total number of squares in the Punnett Square (4)
= 1/4 =
25%
number of squares BB
_______________________________________
Total number of squares in the Punnett Square
=
=
%
number of squares Bb
_______________________________________
Total number of squares in the Punnett Square
=
=
%
number of squares bb
_______________________________________
Total number of squares in the Punnett Square
=
=
%
--------------------------------------------------------------------------------------------------------------------------10. What percentage of the offspring is homozygous for black fur?
11. What percentage of the offspring is heterozygous for black fur?
12. What percentage of the offspring is homozygous for white fur?
13. Would it be likely to observe the same pattern of genotypes in the offspring when two homozygous
parents are crossed? What is the pattern?
`
The presence of hair on the middle section of the fingers (H) is a dominant trait in humans. Two parents
with this dominant trait have children. Some of the children have this trait, and some children do not.
Which of the following Punnett squares shows the genotypes of the parents and children in this family?
Answer the question and place your answer choice here:
Explain your answer:
Glossy leaves are smooth and shiny. What percent of offspring from the cross shown above will have
glossy leaves?
A
B
C
D
0%
25%
50%
100%
Answer the question and place your answer choice here:
Explain your answer: