Question 1

During which phase of the cell cycle does DNA replication occur, and what is the ploidy of the cell immediately after this phase?

Accepted Answer

DNA replication occurs during the S phase, and the cell remains diploid.

Question 2

A human somatic cell in G1 phase contains 46 chromosomes. How many chromatids are present in the cell during metaphase of mitosis?

Accepted Answer

92 chromatids

Question 3

Which of the following best describes the difference between benign and malignant tumors?

Accepted Answer

Benign tumors remain localized, while malignant tumors can metastasize to distant sites.

Question 4

Which checkpoint in the cell cycle ensures that all chromosomes are properly attached to the spindle before proceeding to anaphase?

Accepted Answer

M checkpoint (spindle checkpoint)

Question 5

A cell with 24 chromosomes undergoes meiosis. How many chromosomes will each gamete contain after meiosis is complete?

Accepted Answer

12 chromosomes

Question 6

Which of the following is NOT a source of genetic variation in sexually reproducing species?

Accepted Answer

Replication of DNA during S phase

Question 7

If a plant with genotype $$RrYy is $$crossed with another plant with genotype $$RrYy$$, what is the probability of obtaining an offspring with genotype $$rryy$$? (Assume independent assortment.)

Accepted Answer

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

Question 8

A woman with blood type AB and a man with blood type O have a child. What are the possible blood types of their child?

Accepted Answer

A or B

Question 9

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

Accepted Answer

Autosomal dominant

Question 10

A color-blind woman (X$$^cX$^c) $$marries a man with normal vision (X$$^NY). $$What is the probability that their son will be color-blind?

Accepted Answer

100%

Question 11

Which chromosomal mutation involves a segment of a chromosome being reversed end to end?

Accepted Answer

Inversion

Question 12

Down syndrome is caused by which chromosomal abnormality?

Accepted Answer

Trisomy of chromosome 21

Question 13

If a cell fails to pass the G1 checkpoint, what is the most likely outcome?

Accepted Answer

The cell will enter the G0 phase and stop dividing.

Question 14

Which of the following equations correctly represents the number of possible combinations of chromosomes due to independent assortment in a gamete, where $$n is $$the haploid number?

Accepted Answer

$$2^n$$

Question 15

A pedigree shows a trait that skips generations and is more common in males than females. What is the most likely mode of inheritance?

Accepted Answer

X-linked recessive

Question 16

Which of the following is a requirement for normal cells to continue dividing?

Accepted Answer

Presence of growth factors

Question 17

A male with Klinefelter syndrome has the karyotype 47,XXY. This condition is caused by which meiotic error?

Accepted Answer

Nondisjunction during meiosis

Question 18

Which of the following best describes the difference between a chromosome and a chromatid?

Accepted Answer

A chromatid is one of two identical copies of a chromosome joined at the centromere.

Question 19

In a dihybrid cross between two heterozygous individuals ($$AaBb 	imes AaBb$$), what is the expected phenotypic ratio if both genes show complete dominance and assort independently?

Accepted Answer

9:3:3:1

Question 20

Which of the following disorders is caused by a monosomy?

Accepted Answer

Turner syndrome (45,X)

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