Question 1

Which of the following best describes the chromosomal sex determination system in birds?

Accepted Answer

Females are heterogametic (ZW), males are homogametic (ZZ)

Question 2

In Drosophila melanogaster, what is the sexual phenotype of an individual with the genotype $$XXY$$ and two sets of autosomes ($$AA$$)?

Accepted Answer

Female

Question 3

A woman who is heterozygous for X-linked color blindness ($$X^+X^c) $$has children with a man who is color blind ($$X^cY). $$What is the probability that their son will be color blind?

Accepted Answer

$$0.25$$

Question 4

Which of the following statements about X chromosome inactivation in mammals is CORRECT?

Accepted Answer

Inactivation occurs randomly and early in development, and all but one X chromosome is inactivated in each cell

Question 5

A cross between two yellow mice ($$Yy 	imes Yy) $$produces offspring in a $$2:1$$ ratio of yellow to non-yellow mice. Which genetic phenomenon explains this result?

Accepted Answer

Recessive lethal allele

Question 6

Which of the following best describes the inheritance pattern of mitochondrial DNA in humans?

Accepted Answer

Mitochondrial DNA is inherited only from the mother

Question 7

In a dihybrid cross involving two loci with independent assortment, what is the expected phenotypic ratio in the F2 generation if there is no gene interaction?

Accepted Answer

$$9:3:3:1$$

Question 8

A plant with genotype $$WwYy is $$crossed with another $$WwYy$$ plant. If white fruit color is dominant epistatic to yellow and green, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$12$$ white : $$3$$ yellow : $$1$$ green

Question 9

Which of the following is an example of codominance in humans?

Accepted Answer

ABO blood group, where $$I^A$$ and $$I^B$$ alleles are both expressed in $$I^A I^B$$ individuals

Question 10

A woman with blood type A ($$I^A I^i) $$and a man with blood type O ($$ii) $$have a child with blood type B. What does this suggest?

Accepted Answer

The man cannot be the biological father of the child

Question 11

Which of the following best describes penetrance?

Accepted Answer

The percentage of individuals with a particular genotype that express the expected phenotype

Question 12

In a complementation test, two true-breeding mutant plants are crossed and all offspring have the wild-type phenotype. What does this indicate?

Accepted Answer

The mutations are in different genes

Question 13

Which of the following is a feature of Y-linked inheritance in humans?

Accepted Answer

Traits are passed from fathers to all sons

Question 14

A tortoiseshell cat has patches of black and orange fur. Which genetic mechanism explains this phenotype?

Accepted Answer

Random X chromosome inactivation in heterozygous females

Question 15

Which of the following best describes genomic imprinting?

Accepted Answer

A gene is differentially expressed depending on whether it was inherited from the mother or the father

Question 16

In Labrador retrievers, coat color is determined by two genes: one for pigment color (B = black, b = brown) and one for pigment deposition (E = color, e = no color). What is the phenotype of a dog with genotype $$bb ee$$?

Accepted Answer

Yellow

Question 17

Which environmental factor can influence the phenotype of a genetically identical organism, as seen in hydrangea flower color?

Accepted Answer

Soil pH

Question 18

A temperature-sensitive allele in rabbits produces dark fur only at the extremities when raised at $$25^{\circ}C$ or below. What is this an example of?

Accepted Answer

Environmental impact on gene expression

Question 19

Which of the following is true about the SRY gene in humans?

Accepted Answer

It is located on the Y chromosome and determines male sex

Extensions to the Basic Principles of Heredity: Sex Determination, Sex-Linked Traits, and Gene Interactions

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