Question 1

During which phase of the cell cycle does DNA replication occur, and what is the significance of this phase for mitosis?

Accepted Answer

DNA replication occurs during the S phase, providing each daughter cell with an identical set of chromosomes.

Question 2

A researcher observes a cell with chromosomes aligned at the center of the cell, spindle fibers attached to kinetochores, and no nuclear envelope. Which stage of mitosis is this cell in?

Accepted Answer

Metaphase

Question 3

Which of the following best explains how cancer cells evade normal cell cycle controls?

Accepted Answer

They ignore signals from cell cycle checkpoints, such as those regulated by cyclin-dependent kinases (CDKs).

Question 4

A diploid organism (2n = 8) undergoes meiosis. How many chromosomes will each gamete contain, and what process ensures genetic variation among gametes?

Accepted Answer

Each gamete will have 4 chromosomes; genetic variation is ensured by crossing over and independent assortment.

Question 5

Which of the following scenarios best illustrates independent assortment during meiosis?

Accepted Answer

Homologous chromosomes align randomly at the metaphase I plate, leading to different combinations of maternal and paternal chromosomes in gametes.

Question 6

A woman with genotype $$X^N X^n ($$where $$N is $$normal vision and $$n is $$colorblindness) and a man with genotype $$X^n Y$$ have a child. What is the probability that their son will be colorblind?

Accepted Answer

$$0.25$$

Question 7

Which chromosomal abnormality is characterized by the presence of only one X chromosome and no second sex chromosome (XO), and what syndrome does this cause?

Accepted Answer

Monosomy X; Turner syndrome

Question 8

A plant with genotype $$RrYy ($$where $$R = $$round, $$r = $$wrinkled, $$Y = $$yellow, $$y = $$green) is self-crossed. What is the probability of obtaining an offspring with genotype $$rryy$$?

Accepted Answer

$$\frac{1}{16}$$

Question 9

Which of the following best describes the difference between incomplete dominance and codominance?

Accepted Answer

Incomplete dominance results in a phenotype that is a blend of the two alleles, while codominance results in both alleles being fully expressed.

Question 10

Which enzyme is responsible for synthesizing short RNA primers during DNA replication?

Accepted Answer

Primase

Question 11

A mutation causes a segment of a chromosome to be reversed end to end. What type of chromosomal structural change is this?

Accepted Answer

Inversion

Question 12

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA replication is semiconservative, resulting in each new double helix containing one old and one new strand.

Question 13

A pedigree shows a trait that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 14

Which of the following best explains why males are more likely to express X-linked recessive disorders?

Accepted Answer

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

Question 15

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

Joins Okazaki fragments on the lagging strand

Question 16

A geneticist is studying a trait controlled by two genes, each with two alleles. If the genes assort independently, what is the expected phenotypic ratio in the F2 generation from a dihybrid cross?

Accepted Answer

$$9:3:3:1$$

Question 17

Which of the following is a real-life example of pleiotropy?

Accepted Answer

A single gene in sickle cell anemia affects both red blood cell shape and resistance to malaria.

Question 18

Which process is responsible for correcting errors that occur during DNA replication?

Accepted Answer

Mismatch repair

Question 19

Which of the following best explains the difference between euchromatin and heterochromatin?

Accepted Answer

Euchromatin is loosely packed and transcriptionally active, while heterochromatin is tightly packed and inactive.

Question 20

A woman who is a carrier for hemophilia (an X-linked recessive disorder) and a man without hemophilia have a daughter. What is the probability that the daughter will have hemophilia?

Accepted Answer

$$0.00 ($$since she would need two copies of the recessive allele, and her father does not have hemophilia)

General Biology Study Guide: Cell Cycle, Meiosis, Mendelian Genetics, Chromosomal Inheritance, and DNA Replication

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