Name:

Laboratory Exercise GeneticsMendel’s Principles: Define the following phrases & terms.

1. The principle of segregation.

2. The principle of independent assortment. Explain the scientific evidence which

supports this model

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Vocabulary for Medelian Genetics

1. gamete

2. gene

3. allele

4. dominant allele

5. recessive allele

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6. phenotype

7. genotype

8. homozygous

9. heterozygous

10. reciprocal cross________________________________________________________

11. prue breeding line______________________________________________________

12. Fx__________________________________________________________________

13. Model Organism_______________________________________________________

Genetics Problems

1. Monohybrid Cross.

a. Curled ears in cats is caused by a mutated gene and has been developed into a breed, known as the American Curl. A cat with curled ears was mated with a cat

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with normal ears and all of the offspring have curled ears. Is this trait dominant or recessive? What is the genotype of the curled eared cat?

b. If one of the kittens from the above cross was mated to a cat normal ears what percentage of the offspring will have curled ears?

c. In horses chestnut (red) color is recessive to spotted. If a heterozygous spotted male is crossed to a chestnut female what is the genotypic and phenotypic ratio of the offspring.

d. Congenital night blindness is caused by a dominant autosomal allele B. A man is

heterozygous for night blindness. What is his genotype?____________ Is he

night blind?___________. His wife is normal for the trait. What is her

genotype__________. What is the probability that their first born child will have

night blindness? __________.What is the probability that their second born child

will have night blindness?_________.

e. A man is homozygous for night blindness. What is his genotype? ___________

His wife is normal. What proportion of their children will have night

blindness______________. What proportion of their grandchildren will have

night blindness if all children marry normal spouses?_________

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2. Test Crossa. In pea plants purple flowers (P_) is dominant to white flowers (p_) and tall (T_) is

dominant to short (t_). You have a purple flowered tall plant but you do not know the genotype of this plant.

i. Draw out the Punnett square if this plant is homozygous

ii. Draw out the Punnett square if this plant is heterozygous

b. Short hair is dominant to long hair. If a short-haired animal of unknown origin is crossed with a long-haired animal and they produce one long-haired and one short-haired offspring what is your conclusion about the genotype of the short haired animal.

c. The results of a testcross reveal that all offspring resemble the parent being tested. That parent is _______________________

3. Dihybrid Crossa. In guinea pigs rough coat is dominant over smooth coat and black coat color is

dominant over white coat color. These genes are located on separate chromosomes.

i. Cross a homozygous rough-coated black male with a homozygous smooth-coated white female what is the only phenotype of F1 _______________

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ii. Cross two individuals from F1. Draw out the complete Punnett Square.

Gametes

iii. Proportion of F2 with their parent genotype__________________

iv. Proportion of F2 with their parents phenotype________________

v. Proportion of F2 with their grandmothers genotype_____________

vi. Proportion of F2 with their grandfathers genotype_______________

b. Guinea pigs can also vary in the color of their paws. The allele for red paws is incompletely dominant over white paws. A male guinea pig that has pink paws and black fur Bb is crossed with a female with pink paws and white fur

i. Draw out the Punnett Square

ii. What ratio is Black fur and Red paws_______________

iii. What ratio is Black fur and pink paws_______________

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iv. What ratio is black fur and white paws_______________

v. What ratio is white fur and red paws_________________

vi. What ratio is white fur and pink paws________________

vii. What ratio is white fur and white paws________________

4. Sex Linked Traitsa. Suppose a red-green colorblind woman marries a man with normal color vision.

Draw the Punnett Square

i. What % of the sons will be colorblind____________

ii. What % of the daughters will be colorblind__________

iii. What % of the daugters will be carriers____________

b. Now suppose that one of the daughters from the above cross marries and has children with a normal color vision man. Draw the Punnett Square

i. What % of the daughter will be color blind_____________

ii. What % of the daughters will be carriers________________

iii. What % of the offspring will be affected______________

iv. Are affected individuals male or females_______________

c. In cats B allele produces black fur and b produces orange fur. This gene is X linked. If both alleles are present calico cats are produced. A calico cat has 2 calico kittens, 1 male black kitten, and 1 female orange kitten. Draw the Punnett Square and determine the genotype of the father

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i. What is the genotype of the mother__________phenotype____________

ii. What is the genotype of the father____________phenotype___________

d. What is the best characterization is this genei. Dominant

ii. Recessiveiii. Codominant iv. Incomplete dominance

e. Muscular dystrophies in humans is an X-linked recessive disorder. A woman who is a carrier for this trait has children with a man who is normal. Draw the Punnett square.

i. What is the probability of a son born to them being afflicted with

DMD__________

ii. What is the probability of a daughter being afflicted?___________

iii. What combination of parents must occur for a daughter to have DMD?

Assume at least one parent is unaffected_________&________

f. A normal male marries a normal woman. The man’s father had albinism (aa), but no one in his family had hemophilia. The woman’s mother had albinism and her father had hemophilia. Give the genotypes of the male:_____________ and the female____________

i. List the gametes for the male___________________________

ii. List the gametes for the female_________________________

iii. Draw a Punnett square below for this male and female

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iv. What fraction of the offspring may have hemophilia_________

v. Are they male or female or both_________________________

vi. What fraction of the offspring may have albinism___________

vii. Are they male or female or both_________________________

viii. What fraction of the offspring may have both hemophilia and albinism

5. Codominancea. In the case of disputed paternity Ms. A is type A blood and her child is type O

blood. Two potential fathers are Mr. X with type A blood and Mr. Y with type AB blood. Draw the Punnett square.

i. Who is the father________________

ii. What is Ms. A genotype ______________

If a child belonged to blood type O, he or she could not have been produced by which set of parents?a. Type A mother and type B fatherb. Type A mother and type O fatherc. Type AB mother and type O fatherd. Type O mother and type O fathere. Type O mother and type B father

6. Incomplete Dominancea. In snap dragons R is red flowers and r is white flowers. Heterozygotes show

incomplete dominance. What is the typical genotypic ratio of a cross between two heterozygotes?______________

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b. In terms of gene expression and the production of enzymes explain the mechanism for how incomplete dominance can exist. Under what conditions do heterozygotes assume a dominant phenotype?

7. Explain why the ability to carry oxygen is a polymorphic trait in the human population. How did so many copies of this gene arise in evolution?

8. What is pleiotropy? How does one mutated gene product in sickle cell disease cause pleiotropic effects?

9. Epistasisa. Coat color in mice is determined by two genes which show epistasis. Pigment is

only produced when the N allele is present. Individuals of the nn genotype have no color (white). If color is present it is determined by one of two alleles. Agouti (irregularly patterned barred fur – grizzled appearance) is dominant to black coats.

i. Cross two completely homozygous parents for both traits

ii. Now cross two individuals from F1. Draw the Punnett Square for F2

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A yellow Labrador retriever of the genotype AA ee was crossed with a brown retriever of the genotype aa EE. What would their F1 offspring look like?

a. all yellowb. all brownc. all blackd. 1/2 yellow, 1/2 browne. 1/2 yellow, 1/2 black

10. How does a quantitative trait differ from a discrete trait?

11. Linkage Maps – Separate handout given on Friday 12. Pedigree analysis

13. Label all the genotypes for the following pedigree.

a. Is this trait dominant or recessive?

b. How do you know?

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14. Albinism in humans is caused by the inheritance of a pair of recessive autosomal alleles (aa). Use the given family pedigree to solve the following problems.

a. What are the genotypes of IV1, IV3, IV4, and IV11? _____.

b. What are the genotypes of III2, III3, III7, and III8? _____

c. Assuming II4 is AA, what is the probability that III4 is heterozygous for albinism?

_____%

d. What is the probability that IV6 is homozygous for normal pigmentation? _____%

15. Label the genotypes for this pedigree of an X-linked recessive disorder (red-green colorblindness).

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I

II

III

IV

1 2

1 2 3 4 5 6

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1 2 3 4 5 6

7 8 9 10 11 12 13 14 15 16 17 18

16. Is the following pedigree autosomal recessive, autosomal dominant or X-linked recessive?

a. How do you know?

b. Label the genotypes.

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If all the offspring of a cross had the genotype Aa Bb, the parents of the cross would most likely bea. AA BB aa bb.b. AA bb aa BB.c. Aa Bb Aa Bb.d. Aa bb aa Bb.e. either AA BB x aa bb or AA bb x aa BB.

How many different types of gametes could an Aa Bb Cc individual produce? (Ignore crossing over.)a. 6b. 8c. 9d. 12e. 16

How many different genotypes are produced in the cross Aa Bb Cc Aa Bb Cc?a. 8b. 9c. 12d. 27e. 30

What fraction of the time will the cross of Aa Bb Cc with Aa Bb Cc produce an offspring of genotype aa bb cc?a. 1/64b. 1/32c. 3/64d. 1/16e. 9/64

What fraction of the time will the cross of Aa Bb Cc with Aa Bb Cc produce an offspring that expresses the dominant traits A and B and cc (A_ B_ cc)?a. 1/32b. 3/64c. 1/16d. 9/64e. 27/64

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