Question 1

Which of the following best describes incomplete dominance?

Accepted Answer

The phenotype of the heterozygote is intermediate between the phenotypes of the two homozygotes.

Question 2

A cross between two yellow mice (Yy × Yy) produces offspring in a 2:1 ratio of yellow to non-yellow mice. What is the most likely explanation for this ratio?

Accepted Answer

A recessive lethal allele

Question 3

Which of the following statements about penetrance is correct?

Accepted Answer

Penetrance is the percentage of individuals with a particular genotype who express the expected phenotype.

Question 4

In the ABO blood group system, which genotype(s) result in blood type AB?

Accepted Answer

$$I^A I^B$$

Question 5

A woman with genotype $$hh I^A I^A at $$the H and ABO loci has which blood phenotype?

Accepted Answer

Type O (Bombay phenotype)

Question 6

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects coat color, obesity, and lethality in mice

Question 7

In duplicate recessive epistasis, what phenotypic ratio is expected in the F2 generation from a dihybrid cross ($$AaBb 	imes AaBb$$)?

Accepted Answer

$$9:7$$

Question 8

Which of the following best explains why mitochondrial diseases often show variable expression among siblings?

Accepted Answer

Mitochondria segregate randomly during cell division, leading to different proportions of mutant and wild-type mitochondria in cells.

Question 9

A goat with genotype $$B^+B^b is $$bearded if male but beardless if female. This is an example of:

Accepted Answer

Sex-influenced inheritance

Question 10

Which of the following is true about genomic imprinting?

Accepted Answer

Expression of an allele depends on whether it was inherited from the mother or the father.

Question 11

A Siamese cat has dark fur on its extremities due to a temperature-sensitive allele. What is the molecular basis for this phenotype?

Accepted Answer

The enzyme responsible for pigment production is only active at lower temperatures.

Question 12

Which of the following crosses would you use to perform a complementation test?

Accepted Answer

Cross two individuals with the same phenotype to see if their offspring are wild-type.

Question 13

Which of the following is a characteristic of cytoplasmically inherited traits?

Accepted Answer

They are usually inherited from the maternal parent.

Question 14

A phenocopy is best described as:

Accepted Answer

A phenotype caused by an environmental agent that mimics a genetic mutation.

Question 15

In a dihybrid cross ($$AaBb 	imes AaBb) $$showing dominant epistasis, what is the expected phenotypic ratio?

Accepted Answer

$$12:3:1$$

Question 16

Which of the following best describes a compound heterozygote?

Accepted Answer

An individual with two different mutant alleles at a locus.

Question 17

A snail's shell coiling direction is determined by the genotype of its mother, not its own genotype. This is an example of:

Accepted Answer

Genetic maternal effect

Question 18

Which of the following is a real-world application of pronuclear transfer in humans?

Accepted Answer

To prevent the transmission of mitochondrial genetic diseases

Question 19

Which of the following best describes codominance?

Accepted Answer

Both alleles in the heterozygote are fully expressed.

Question 20

Which of the following is an example of a quantitative (polygenic) characteristic?

Accepted Answer

Height in humans

Extensions and Modifications of Basic Principles in Genetics

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