Question 1

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

Accepted Answer

It leads to a reduction or elimination of the normal activity of the gene product.

Question 2

In snapdragons, a cross between a red-flowered plant ($$R^R) $$and a white-flowered plant ($$R^W) $$produces pink-flowered offspring. What type of inheritance does this illustrate?

Accepted Answer

Incomplete dominance

Question 3

A person with the genotype $$I^A I^B$$ for the ABO blood group will have which blood type?

Accepted Answer

Type AB

Question 4

Which of the following statements about codominance is correct?

Accepted Answer

Both alleles are fully expressed in the heterozygote.

Question 5

A woman with the Bombay phenotype is genetically $$I^A I^B$$ but has blood type O. What is the molecular explanation for this?

Accepted Answer

She is homozygous for a mutation in the FUT1 gene, preventing the production of the H substance.

Question 6

Which of the following genotypes would result in a lethal phenotype in mice with the agouti gene?

Accepted Answer

$$A^Y A^Y$$

Question 7

If two heterozygous snapdragons ($$R^R R^W) $$are crossed, what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

$$1:2:1 ($$red:pink:white)

Question 8

Which of the following is true regarding essential genes?

Accepted Answer

A single wild-type allele is sufficient for survival if the other allele is mutated.

Question 9

A man with blood type AB and a woman with blood type O have a child. What is the probability that the child will have blood type B?

Accepted Answer

$$0.5$$

Question 10

Which of the following best describes a neutral mutation?

Accepted Answer

It does not affect the phenotype or evolutionary fitness of the organism.

Question 11

In a dihybrid cross involving two gene pairs, both showing independent assortment, what is the expected phenotypic ratio in the F2 generation if both traits show complete dominance?

Accepted Answer

$$9:3:3:1$$

Question 12

Which of the following is an example of a dominant lethal allele in humans?

Accepted Answer

Huntington disease

Question 13

A geneticist uses the notation $$e^+ to $$represent an allele. What does this notation indicate?

Accepted Answer

A wild-type allele

Question 14

Which of the following best explains the threshold effect observed in Tay-Sachs disease?

Accepted Answer

A normal phenotype is observed as long as a certain minimum level of gene product is produced.

Question 15

Which of the following is true about multiple alleles?

Accepted Answer

They involve three or more alleles of the same gene in a population.

Question 16

In the context of gene interaction, which of the following statements is correct?

Accepted Answer

A single phenotype can be affected by more than one set of genes.

Question 17

A cross between two yellow mice ($$A^Y A) $$produces offspring in a 2:1 ratio of yellow to agouti. What explains the absence of some expected genotypes?

Accepted Answer

The $$A^Y$$ allele is dominant for color but recessive lethal when homozygous.

Question 18

Which of the following is the correct representation for a heterozygous wild-type and mutant allele in Drosophila using standard genetic notation?

Accepted Answer

$$e^+ / e$$

Question 19

If a trait shows incomplete dominance, what would be the expected genotypic and phenotypic ratios in the F2 generation from a cross between two heterozygotes?

Accepted Answer

Genotypic ratio $$1:2:1$$, phenotypic ratio $$1:2:1$$

Question 20

Which of the following best describes the inheritance pattern of the MN blood group in humans?

Accepted Answer

Codominance

Extensions of Mendelian Genetics: Key Concepts and Applications

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