Question 1

Which of the following best explains why Mendel observed 3:1 and 9:3:3:1 ratios in his mono- and di-hybrid crosses?

Accepted Answer

He only observed two alleles at each locus and all loci assorted independently.

Question 2

A cross between two snapdragons, one red (RR) and one white (rr), produces pink (Rr) offspring. What type of inheritance does this demonstrate?

Accepted Answer

Incomplete dominance

Question 3

In Tay-Sachs disease, heterozygotes have approximately 50% of normal enzyme activity, but do not show symptoms. Which genetic concept does this illustrate?

Accepted Answer

Threshold effect

Question 4

Which of the following is true about codominance?

Accepted Answer

Both alleles in a heterozygote are fully and distinctly expressed.

Question 5

A woman with the Bombay phenotype has genotype hh at the FUT1 locus. What is the consequence for her ABO blood group antigens?

Accepted Answer

She cannot produce A or B antigens, regardless of her ABO genotype.

Question 6

If two yellow mice (genotype $$A^Y A) $$are crossed, what is the expected ratio of yellow to non-yellow offspring, given that $$A^Y A^Y is $$lethal?

Accepted Answer

$$2:1$$ yellow to non-yellow

Question 7

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

Accepted Answer

A mutation that eliminates the activity of the wild-type gene product.

Question 8

In the ABO blood group system, which genotype(s) can produce type O blood?

Accepted Answer

ii

Question 9

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

Accepted Answer

Huntington disease

Question 10

A cross between two MN blood type parents (genotype $$L^M L^N) $$can produce offspring with which possible blood types?

Accepted Answer

M, MN, and N

Question 11

Which of the following scenarios best illustrates gene interaction?

Accepted Answer

Multiple genes contribute to the development of the inner ear, and mutations in any of them can cause hereditary deafness.

Question 12

Which of the following is NOT a reason Mendel observed simple ratios in his experiments?

Accepted Answer

He studied traits influenced by multiple genes and environmental factors.

Question 13

Which of the following is true about multiple alleles?

Accepted Answer

They can only be studied in populations, not individuals.

Question 14

Which formula represents the expected genotypic ratio for a monohybrid cross showing incomplete dominance?

Accepted Answer

$$1:2:1$$

Question 15

Which of the following best describes epistasis?

Accepted Answer

The effect of one gene is dependent on the presence of one or more 'modifier genes' at different loci.

Question 16

A geneticist observes a 2:1 ratio in the offspring of a cross. Which scenario is most likely responsible for this ratio?

Accepted Answer

A recessive lethal allele eliminates one genotype from the population.

Question 17

Which of the following is a neutral mutation?

Accepted Answer

A mutation that does not change the phenotype or evolutionary fitness.

Question 18

Which of the following is true about wild-type alleles?

Accepted Answer

They occur most frequently in nature and are usually, but not always, dominant.

Question 19

Which equation represents the expected phenotypic ratio for a dihybrid cross with independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 20

Which of the following is an example of a heterogeneous trait?

Accepted Answer

Hereditary deafness caused by mutations in any of several different genes.

Extensions of Mendelian Genetics: Beyond Simple Inheritance Patterns

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