Question 1

A cross between two true-breeding snapdragon plants, one with red flowers and one with white flowers, produces F1 offspring with pink flowers. What type of dominance is illustrated by this result?

Accepted Answer

Incomplete dominance

Question 2

In a certain mouse population, a gene for coat color has three alleles: $$A$$, $$B$$, and $$C. $$How many possible genotypes can exist at this locus?

Accepted Answer

$$9$$

Question 3

A geneticist observes that a particular allele causes death when homozygous, but not when heterozygous. In a cross between two heterozygotes, the observed progeny ratio is 2:1 instead of the expected 3:1. What is the most likely explanation?

Accepted Answer

Lethal allele

Question 4

Which of the following best describes penetrance?

Accepted Answer

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

Question 5

A cross between two dihybrid pea plants ($$RrYy 	imes RrYy) $$produces offspring with a phenotypic ratio of 9:7 instead of the expected 9:3:3:1. What genetic phenomenon is most likely responsible for this result?

Accepted Answer

Duplicate recessive epistasis

Question 6

Which equation would you use to calculate the expected number of individuals with a specific phenotype in a dihybrid cross with a 9:3:3:1 ratio, if there are $$N$$ total progeny?

Accepted Answer

$$\frac{9}{16} 	imes N$$

Question 7

A researcher is studying a trait that is only expressed in males, even though both sexes carry the gene. What type of inheritance is this?

Accepted Answer

Sex-limiting inheritance

Question 8

Which of the following statements about cytoplasmic inheritance is correct?

Accepted Answer

It is typically inherited from the mother because the egg contributes most of the cytoplasm

Question 9

A child inherits a genetic disorder only if the defective allele is inherited from the mother, but not if inherited from the father. What is this phenomenon called?

Accepted Answer

Genomic imprinting

Question 10

Which of the following best describes epigenetics?

Accepted Answer

Changes in gene expression that do not involve changes to the DNA sequence

Question 11

A man with type AB blood and a woman with type O blood have children. What are the possible blood types of their children?

Accepted Answer

A and B only

Question 12

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both fur color and hearing in cats

Question 13

A trait is controlled by several genes, each contributing a small additive effect to the phenotype. What is this type of inheritance called?

Accepted Answer

Polygenic inheritance

Question 14

In a population, a gene shows 80% penetrance. If 100 individuals have the genotype, how many are expected to show the phenotype?

Accepted Answer

$$80$$

Question 15

Which of the following best distinguishes between sex-linked and sex-influenced inheritance?

Accepted Answer

Sex-linked genes are located on sex chromosomes, while sex-influenced genes are on autosomes but expressed differently in males and females

Question 16

A geneticist is analyzing a cross and finds that the phenotypic ratio among the offspring is 12:3:1. Which type of gene interaction is most likely responsible?

Accepted Answer

Dominant epistasis

Question 17

Which of the following is an example of a quantitative characteristic?

Accepted Answer

Height in humans

Question 18

A Himalayan rabbit has dark fur on its ears, nose, and feet, but white fur elsewhere. When raised in a warm environment, the dark fur is reduced. What does this demonstrate?

Accepted Answer

Gene-environment interaction

Question 19

Which of the following best describes the difference between expressivity and penetrance?

Accepted Answer

Penetrance is the percentage of individuals with a genotype showing the phenotype, while expressivity is the degree to which the phenotype is expressed

Question 20

In a dihybrid cross, you observe the following progeny numbers: 90, 30, 30, and 10. If the expected ratio is 9:3:3:1 and the total number of progeny is 160, what is the expected number for the smallest class?

Accepted Answer

$$10$$

Extensions and Modifications of Basic Principles in Genetics

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