Question 1

Which of the following best explains why DNA must be in an open chromatin state during the S phase of the cell cycle?

Accepted Answer

Open chromatin allows the enzymes responsible for DNA replication to access and copy the genetic material.

Question 2

A researcher observes a cell with visible condensed chromosomes aligned at the center of the cell. Which phase of mitosis is this cell most likely in?

Accepted Answer

Metaphase

Question 3

Which of the following statements correctly distinguishes between mitosis and meiosis?

Accepted Answer

Mitosis produces two diploid cells, while meiosis produces four haploid cells.

Question 4

A human cell with 46 chromosomes undergoes meiosis. How many chromosomes will each resulting gamete contain?

Accepted Answer

$$23$$

Question 5

A woman with genotype $$X X$$ and a man with genotype $$X Y$$ have a child. Which statement about the inheritance of the SRY gene is correct?

Accepted Answer

Only children who inherit the $$Y$$ chromosome from their father will have the SRY gene.

Question 6

A person with androgen insensitivity syndrome has an $$X Y$$ genotype but develops as female. What is the most likely explanation for this?

Accepted Answer

Their cells cannot respond to testosterone, so male development does not occur.

Question 7

In Mendel’s pea plant experiments, tall plants ($$T) $$are dominant to short plants ($$t). If $$two heterozygous tall plants ($$Tt) $$are crossed, what is the expected phenotypic ratio of their offspring?

Accepted Answer

$$3$$ tall : $$1$$ short

Question 8

A test cross is performed between a plant with an unknown genotype showing a dominant trait and a plant with a recessive phenotype. What is the purpose of this test cross?

Accepted Answer

To determine whether the dominant-appearing plant is homozygous or heterozygous for the trait.

Question 9

Which of the following is an example of incomplete dominance?

Accepted Answer

A cross between red-flowered and white-flowered plants produces pink-flowered offspring.

Question 10

Which process during meiosis is primarily responsible for the genetic diversity observed in siblings (excluding identical twins)?

Accepted Answer

Independent assortment and crossing over

Question 11

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

Accepted Answer

A or B only

Question 12

If a cell spends most of its life in the $$G_0$$ phase, what is it primarily doing?

Accepted Answer

Performing its normal, specialized functions without dividing

Question 13

Which of the following best describes polygenic inheritance?

Accepted Answer

A trait is influenced by multiple genes, resulting in a wide range of phenotypes.

Question 14

A genetic counselor is working with a couple who both carry a recessive allele for cystic fibrosis ($$Ff). $$What is the probability that their child will have cystic fibrosis?

Accepted Answer

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

Question 15

During which phase of the cell cycle are organelles such as mitochondria doubled in preparation for cell division?

Accepted Answer

G2 phase

Question 16

A cell is observed to have two chromatids per chromosome and is preparing to divide. Which phase has it just completed?

Accepted Answer

S phase

Question 17

Which of the following scenarios best illustrates codominance?

Accepted Answer

A person with type AB blood expresses both A and B antigens equally.

Question 18

If a genetic disorder is caused by a dominant allele, what is the minimum genotype required for an individual to express the disorder?

Accepted Answer

At least one dominant allele (heterozygous or homozygous dominant)

Question 19

Which of the following is true about the number of genes on the human X and Y chromosomes?

Accepted Answer

The X chromosome has about 1,100 genes, while the Y chromosome has about 78 genes.

Cell Cycle, Chromosome Dynamics, and Patterns of Inheritance

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