Question 1

Gregor Mendel observed a 3:1 ratio of dominant to recessive phenotypes in the F2 generation of pea plants. Which of the following best explains this observation?

Accepted Answer

Each plant inherits two alleles for each trait, and alleles segregate independently during gamete formation.

Question 2

Which of the following equations represents the expected genotypic ratio in the F2 generation for a monohybrid cross according to Mendelian genetics?

Accepted Answer

$$1:2:1$$

Question 3

A diploid cell with genotype AaBb undergoes meiosis. Assuming independent assortment, what is the expected ratio of gamete genotypes produced?

Accepted Answer

$$1:1:1:1$$ \ (AB:Ab:aB:ab)$

Question 4

Which stage of the cell cycle is responsible for DNA replication?

Accepted Answer

S phase

Question 5

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Sister chromatids are identical copies formed after DNA replication; homologous chromosomes are similar but may carry different alleles.

Question 6

Which of the following is a real-world example of incomplete dominance?

Accepted Answer

Snapdragon flower color, where crossing red and white yields pink offspring

Question 7

A cross between two yellow mice (genotype $$A^Y a) $$produces a 2:1 ratio of yellow to agouti offspring. What is the most likely explanation for this result?

Accepted Answer

The yellow allele is lethal when homozygous ($$A^Y A^Y$$ individuals die).

Question 8

Which of the following best describes codominance, as seen in human blood types?

Accepted Answer

Both alleles are fully expressed in the heterozygote.

Question 9

A woman with blood type AB ($$I^A I^B) $$and a man with blood type O ($$ii) $$have children. What are the possible blood types of their children?

Accepted Answer

A and B only

Question 10

Which of the following is an example of a conditional allele?

Accepted Answer

The Himalayan allele in rabbits, which produces pigment only at low temperatures

Question 11

In Morgan’s experiments with Drosophila, why did reciprocal crosses between red-eyed and white-eyed flies yield different results?

Accepted Answer

The white gene is X-linked, so inheritance depends on the sex of the parent carrying the allele.

Question 12

Which of the following best defines penetrance?

Accepted Answer

The percentage of individuals with a mutant genotype who show the mutant phenotype.

Question 13

A geneticist observes that all individuals with genotype bb do not show the same severity of the mutant phenotype. What is this phenomenon called?

Accepted Answer

Variable expressivity

Question 14

Which of the following is true about the products of mitosis and meiosis?

Accepted Answer

Mitosis produces two identical diploid cells; meiosis produces four genetically different haploid cells.

Question 15

Which of the following best explains why Siamese cats have darker fur on their extremities?

Accepted Answer

A temperature-sensitive allele produces pigment only in cooler areas of the body.

Question 16

Which of the following is an example of a sex-influenced trait?

Accepted Answer

The bearded phenotype in goats, which is dominant in males but recessive in females

Question 17

Which of the following best describes the molecular explanation for Mendelian complete dominance?

Accepted Answer

The dominant allele produces enough functional protein to mask the effect of the recessive allele.

Question 18

A population of cats with white fur and blue eyes shows that about 40% are born deaf. What genetic concept does this illustrate?

Accepted Answer

Pleiotropy

Question 19

Which of the following is a key feature of Mendel’s seven pea plant traits that made them ideal for studying inheritance patterns?

Accepted Answer

Each trait showed complete dominance and 100% penetrance.

Question 20

Which of the following best describes the law of independent assortment?

Accepted Answer

Alleles for different traits segregate independently into gametes during meiosis.

Transmission Genetics and Modifications to Mendelian Inheritance

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