Question 1

Which of the following statements best describes the chromosome theory of inheritance?

Accepted Answer

Genes are located on chromosomes, and the behavior of chromosomes during meiosis accounts for inheritance patterns.

Question 2

In Morgan’s experiments with Drosophila, why did only male flies have white eyes in the F2 generation when a white-eyed male was crossed with a red-eyed female?

Accepted Answer

The gene for eye color is located on the X chromosome, and males have only one X chromosome.

Question 3

Which of the following best explains why X-linked recessive disorders are more common in males than in females?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will cause the disorder.

Question 4

A woman who is heterozygous for the X-linked gene for color blindness (X	extsuperscript{N}X	extsuperscript{n}) marries a man with normal vision (X	extsuperscript{N}Y). What is the probability that their son will be color blind?

Accepted Answer

$$\frac{1}{2}$$

Question 5

Which process is responsible for the production of recombinant chromosomes in linked genes?

Accepted Answer

Crossing over during prophase I of meiosis

Question 6

If two genes are 10 map units apart on a chromosome, what is the expected recombination frequency between them?

Accepted Answer

$$10\%$$

Question 7

A child is born with Down syndrome. Which chromosomal abnormality is most likely responsible?

Accepted Answer

Trisomy 21

Question 8

Which of the following chromosomal alterations results in a segment of a chromosome being repeated?

Accepted Answer

Duplication

Question 9

A female mammal is heterozygous for a gene on the X chromosome. Due to X inactivation, what is the expected result in her somatic cells?

Accepted Answer

She will be a mosaic, with some cells expressing one allele and some expressing the other.

Question 10

Which of the following best describes genomic imprinting?

Accepted Answer

The expression of an allele depends on whether it is inherited from the mother or the father.

Question 11

A plant with a triploid (3n) chromosome number is an example of which genetic phenomenon?

Accepted Answer

Polyploidy

Question 12

Which of the following is a real-life example of a disorder caused by a chromosomal translocation?

Accepted Answer

Chronic myelogenous leukemia (CML)

Question 13

A woman with mitochondrial myopathy has children with a healthy man. What is the expected inheritance pattern for this disorder?

Accepted Answer

All of her children may inherit the disorder, regardless of sex.

Question 14

Which of the following best explains why genes that are far apart on the same chromosome can have a recombination frequency near 50%?

Accepted Answer

Multiple crossovers can occur between them, making them behave as if they are on different chromosomes.

Question 15

A male with Klinefelter syndrome has which of the following sex chromosome compositions?

Accepted Answer

XXY

Question 16

Which of the following is NOT a possible result of nondisjunction during meiosis?

Accepted Answer

A zygote with the normal diploid number of chromosomes

Question 17

Which of the following statements about linked genes is correct?

Accepted Answer

They tend to be inherited together because they are located near each other on the same chromosome.

Question 18

A testcross between a dihybrid fruit fly (b+ vg+/b vg) and a double mutant (b vg/b vg) yields 85% parental-type offspring and 15% recombinant offspring. What is the recombination frequency between the two genes?

Accepted Answer

$$15\%$$

Question 19

Which of the following is a consequence of X inactivation in female mammals?

Accepted Answer

Some female mammals, such as tortoiseshell cats, display mosaic phenotypes.

Question 20

Which of the following best describes the inheritance of extranuclear genes?

Accepted Answer

They are inherited maternally because the zygote’s cytoplasm comes from the egg.

The Chromosomal Basis of Inheritance: Study Notes for General Biology

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