Question 1

Which of the following best describes the genetic mechanism underlying the Bombay phenotype in human ABO blood groups?

Accepted Answer

A mutation in the FUT1 gene prevents the formation of the H substance, masking the expression of ABO alleles.

Question 2

In a cross between two heterozygous snapdragons (Rr), where R is the allele for red flowers and r is the allele for white flowers, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

1 red : 2 pink : 1 white

Question 3

Which equation describes the proportion of F2 individuals expressing either extreme phenotype in a polygenic trait controlled by n gene pairs?

Accepted Answer

$$\frac{1}{4^n}$$

Question 4

A mouse with genotype 'bb' at the coat color locus is albino regardless of its genotype at the 'A' locus. This is an example of:

Accepted Answer

Recessive epistasis

Question 5

Which of the following best explains why Huntington's disease is inherited as a dominant lethal allele but persists in human populations?

Accepted Answer

The disease manifests after reproductive age, allowing carriers to pass on the allele before symptoms appear.

Question 6

In Drosophila, the 'e' allele causes an ebony body color, while the wild-type allele 'e+' results in gray. What is the phenotype of an 'e+/e' heterozygote?

Accepted Answer

Gray

Question 7

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causing cardiac anomalies, lens dislocation, and increased bone length in Marfan syndrome.

Question 8

Pattern baldness in humans is an example of:

Accepted Answer

Sex-influenced inheritance

Question 9

A cross between two AaBb individuals for two independent traits, where both traits show simple dominance, will result in which phenotypic ratio in the F2 generation?

Accepted Answer

9:3:3:1

Question 10

Which of the following best describes codominance?

Accepted Answer

Both alleles are fully expressed in the heterozygote, resulting in distinct detectable products.

Question 11

In a complementation analysis, two Drosophila mutants with the same phenotype are crossed. All offspring have normal wings. What does this indicate?

Accepted Answer

The mutations are in different genes (genic effect).

Question 12

Which of the following best describes penetrance?

Accepted Answer

The probability that a disease phenotype will be present when the genotype is present.

Question 13

A cross between two AaBb individuals for two traits, where one trait shows dominant epistasis, will result in which phenotypic ratio?

Accepted Answer

12:3:1

Question 14

Which of the following is a real-world example of a nutritional mutation affecting phenotype?

Accepted Answer

Phenylketonuria (PKU) can be managed by altering diet to restore normal phenotype.

Question 15

Which equation represents the probability of observing a recessive phenotype in the F2 generation of a monohybrid cross?

Accepted Answer

$$\frac{1}{4}$$

Question 16

Which of the following best describes genetic anticipation?

Accepted Answer

Symptoms of a genetic disorder appear at an earlier age and with increased severity in successive generations.

Question 17

In the context of genetic imprinting, which statement is correct?

Accepted Answer

The phenotypic effect of an allele depends on which parent it is inherited from.

Question 18

Which of the following is an example of environmental influence on phenotype?

Accepted Answer

The dark fur patches in Himalayan rabbits are due to a temperature-sensitive allele.

Question 19

Which of the following best describes the effect of a loss-of-function mutation?

Accepted Answer

The mutation causes a reduction or complete loss of the specific wild-type function.

Question 20

In a dihybrid cross involving complementary gene interaction, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

9:7

Extensions of Mendelian Genetics: Comprehensive Study Guide

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