Question 1

During which phase of the cell cycle does DNA replication occur, and what is the result for each chromosome after this phase?

Accepted Answer

DNA replication occurs during the S phase, resulting in each chromosome having two sister chromatids.

Question 2

Which of the following best describes the difference between mitosis and meiosis?

Accepted Answer

Mitosis produces diploid somatic cells, while meiosis produces haploid gametes.

Question 3

A cell is observed with homologous chromosomes paired at the metaphase plate, each consisting of two sister chromatids. Which stage is this cell in?

Accepted Answer

Metaphase I of meiosis

Question 4

Which chromosomal event is the physical basis for Mendel's law of independent assortment?

Accepted Answer

Random alignment of homologous chromosome pairs at metaphase I

Question 5

A geneticist observes a 9:7 phenotypic ratio in the F2 generation of a dihybrid cross. What is the most likely explanation for this ratio?

Accepted Answer

Complementary gene interaction (both genes required for phenotype)

Question 6

Which of the following chromosomal rearrangements can result in a gene dosage effect, potentially leading to developmental disorders?

Accepted Answer

Duplication

Question 7

A woman is a carrier for a recessive genetic disorder. If the gene shows incomplete penetrance, which of the following is true?

Accepted Answer

Some individuals with the genotype will not express the phenotype.

Question 8

In a cross between two heterozygotes for a single gene showing codominance, what is the expected phenotypic ratio in the offspring?

Accepted Answer

$$1:2:1$$

Question 9

Which of the following best describes nondisjunction, and what is a possible consequence in humans?

Accepted Answer

Failure of chromosomes to separate during anaphase; can result in trisomy 21 (Down syndrome).

Question 10

A test cross is performed between an individual with an unknown genotype and a homozygous recessive individual. What is the main purpose of this cross?

Accepted Answer

To determine whether the unknown individual is homozygous or heterozygous for a dominant allele.

Question 11

If two genes are located close together on the same chromosome, which of the following is most likely to occur?

Accepted Answer

They will be inherited together more often than not (genetic linkage).

Question 12

Which of the following is an example of pleiotropy?

Accepted Answer

A gene that affects both hair color and bone density.

Question 13

A plant with genotype AaBb is testcrossed with aabb. If the genes are unlinked, what proportion of the offspring are expected to be AaBb?

Accepted Answer

$$\frac{1}{4}$$

Question 14

Which of the following best explains the phenomenon of dominant epistasis?

Accepted Answer

A dominant allele at one gene masks the effect of alleles at a second gene.

Question 15

In a complementation test, two mutants with similar phenotypes are crossed. The offspring all display the wild-type phenotype. What does this indicate?

Accepted Answer

The mutations are in different genes.

Question 16

A pedigree shows a trait that appears in every generation and affects both males and females equally. Which inheritance pattern is most likely?

Accepted Answer

Autosomal dominant

Question 17

Which of the following is a likely outcome of a chromosomal inversion?

Accepted Answer

Interference with crossing over during meiosis

Question 18

A genetic cross yields a 9:3:4 phenotypic ratio in the F2 generation. What type of gene interaction does this suggest?

Accepted Answer

Recessive epistasis

Question 19

Which of the following best describes the role of spindle fibers during mitosis and meiosis?

Accepted Answer

They attach to centromeres and help separate chromosomes or chromatids.

Question 20

A human cell at metaphase II of meiosis contains 23 chromosomes. How many DNA molecules (chromatids) are present at this stage?

Accepted Answer

$$46$$

Cell Division, Chromosome Heredity, and Inheritance Patterns: Study Guide

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