Question 1

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

Accepted Answer

Each plant has two copies of a factor (gene), and alleles segregate randomly during gamete formation.

Question 2

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 maternal and paternal versions that may carry different alleles.

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 phase of the cell cycle is responsible for DNA replication?

Accepted Answer

S phase

Question 5

In a cross between two heterozygous snapdragon plants (Pp), where P shows incomplete dominance over p, what phenotypic ratio is expected in the offspring?

Accepted Answer

$$1:2:1$$ \ (purple: violet: white)

Question 6

A woman with blood type AB and a man with blood type O have children. Which blood types are possible for their children?

Accepted Answer

A and B only

Question 7

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 8

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

Accepted Answer

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

Question 9

Which of the following is an example of codominance?

Accepted Answer

A person with genotype $$I^A I^B$$ has both A and B antigens on their red blood cells.

Question 10

A geneticist observes that not all individuals with the genotype bb show the mutant phenotype, and those that do show varying severity. What genetic concepts are being observed?

Accepted Answer

Incomplete penetrance and variable expressivity

Question 11

Which of the following statements about X-linked inheritance is correct?

Accepted Answer

A male with an X-linked recessive allele will express the trait if his mother carries the allele.

Question 12

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 13

Which of the following is a real-world example of a conditional allele?

Accepted Answer

The Himalayan allele for rabbit coat color, which is temperature-sensitive

Question 14

A trait is only expressed in males, even though the gene is autosomal. This is an example of:

Accepted Answer

Sex-limited trait

Question 15

Which of the following best explains why the F1 generation in Morgan’s white-eyed fruit fly cross all had red eyes, but only males had white eyes in the F2 generation?

Accepted Answer

The white gene is X-linked, and males only have one X chromosome.

Question 16

Which of the following is NOT a modification to simple Mendelian inheritance?

Accepted Answer

Complete dominance with 100% penetrance

Question 17

A population of cats with white fur and blue eyes shows that about 40% are born deaf. This is an example of:

Accepted Answer

Pleiotropy

Question 18

Which of the following best describes the outcome of mitosis in a diploid organism?

Accepted Answer

Two genetically identical diploid cells

Question 19

Which of the following is true about the behavior of chromosomes during meiosis and Mendel’s laws?

Accepted Answer

Chromosome behavior during meiosis explains Mendel’s laws of segregation and independent assortment.

Question 20

A gene shows variable expressivity. Which of the following would you expect to observe in a population?

Accepted Answer

Individuals with the mutant genotype show a range of phenotypic severity.

Transmission Genetics and Modifications to Mendelian Inheritance

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