Exam 4 Review

Question 1

Mendel’s Law of Segregation says:

Answer 1

2 copies of genetic information for a trait, each will be passed onto 50% of gametes

Question 2

Crosses that result in 2:1 phenotypic ratio of offspring suggests;

Answer 2

lethal allele

Question 3

In dosage compensation, females have the same amount of X-linked gene products as males due to:

Answer 3

the inactivation of one X chromosome in all somatic cells of females

Question 4

How many Barr bodies would be found in an XXXY male have?

Answer 4

2

Question 5

Which sex chromosome condition is lethal?

Answer 5

YO

Question 6

Which of the following mechanisms of sex determination is found in nature?

Answer 6

chromosomal, geneic, environmental temperature

Question 7

A woman with type B blood has children with a man who has Type A blood. They are both heterozygous with respect to the I gene. All genotypes possible for the children are;

Answer 7

a. IaIb, Iai, Ibi, ii

Question 8

Ernest Hemingway is (at least partly) famous for the numerous polydactyl cats he kept at his home in Florida. You can still find polydactyl cats there today. Some cats have 6 toes on one foot, some have 6 toes on all four feet. Some even have 7 toes on one foot. Toe number here is a good example of.

Answer 8

expressivity

Question 9

If a single trait is controlled by two genes and a dihybrid cross gives a 9:3:3:1, it is likely that:

Answer 9

the two genes work in parallel pathways

Question 10

Two yellow carrots are crossed and give the following offspring: 42 oranges, 170 yellow, 14 white. What is the likely mode of inheritance controlling carrot color?

Answer 10

epistasis

Question 11

In ABO blood types Ia and Ib alleles are ________ to each other, and both are _______ to the I allele.

Answer 11

codominant, dominant

Question 12

Human gonads do not begin male or female differentiation until _____ weeks of embryonic development.

Answer 12

8

Question 13

Humans have ______ sets of autosomes and ____ sets of sex chromosome.

Answer 13

22; 1

Question 14

True or false; the Y-chromosome contains many more genes than the X-chromosome.

Answer 14

false

Question 15

What is the number of individuals with a genotype that express the expected phenotype.

Answer 15

Penetrance

Question 16

cytoplasmic inheritance

Answer 16

chloroplast gene determines the phenotype

Question 17

sex-limited trait

Answer 17

autosomal gene expressed in only one sex

Question 18

sex-influenced

Answer 18

autosomal gene more expressed in one sex

Question 19

genetic imprinting

Answer 19

gene expression affected by the sex of parent passing on the chromosome

Question 20

AaxAa ratio?

Answer 20

2:1, 3:1, 1:2:1

Question 21

AA x Aa ratio?

Answer 21

2:1, 1:1

Question 22

AaBb x AaBb

Answer 22

9:3:4, 9:6:1

Question 23

AaBb x aabb

Answer 23

1:1:1:1

Question 24

What causes the 9:3:4 ratio in Labrador retrievers.

Answer 24

It occurs because even if the black or brown pigment is present, if the ability to deposit the pigment isn’t dominant then the lab will be yellow. With B_ee, even though the black pigment is present it can’t be deposited.

Question 25

Compare complete, incomplete dominance, and co-dominance in terms of dosage.

Answer 25

Complete dominance occurs because one dose of the homozygous dominant produces the same phenotypes as one dose of the protein by the heterozygous alleles.
Incomplete dominance occurs because there is less dosage of proteins in the heterozygous than the homozygous protein dosage resulting in an intermediate phenotype.
Co-dominance occurs because 1 dose of both alleles are expressed resulting in a new combined phenotype.

Question 26

What are the requirements for typical male pattern development.

Answer 26

For typical male pattern development an X and Y chromosome is required. The Y chromosome has the SRY gene which initiates testosterone production. Testosterone is the male sex hormone which causes, the undifferentiated gonads to become testes and develops the Wolffian ducts, MIH is also required which is Mullerian inhibiting hormone which degrades the Müllerian ducts.

Question 27

Provide a genetic and hormonal explanation for androgen insensitivy syndrome in an X-Y female.

Answer 27

Androgen insensitivity in an XY female because there is a mutation in the androgen receptor (AR) gene which mutates the testosterone receptor making it unable to bind testosterone. This causes the Wolfian duct system to degrade and phenotypic female genetalia to form. MIH is still made though so the mullerian ducts still degrade resulting in a phenotypic female with no reproductive organs

Question 28

What are the reasons for autosomal recessive in a pedigree?

Answer 28

1. the trait skips a generation
2. two unaffected people have an affected kid