Question 1

Which of the following statements correctly differentiates between somatic cells and gametes in humans?

Accepted Answer

Somatic cells are diploid ($$2n$$), while gametes are haploid ($$n).$$

Question 2

A pea plant with genotype $$Tt ($$where $$T is $$tall and $$t is $$short) is crossed with another $$Tt$$ plant. What is the expected phenotype ratio in the offspring?

Accepted Answer

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

Question 3

During which stage of meiosis does crossing over occur, and what is its significance?

Accepted Answer

Crossing over occurs during prophase I and increases genetic variation.

Question 4

Which of the following best describes the law of independent assortment?

Accepted Answer

Each pair of alleles segregates independently of other pairs during gamete formation.

Question 5

A woman who is a carrier for an X-linked recessive disorder ($$X^NX^n) $$and a man who is unaffected ($$X^NY) $$have a son. What is the probability that their son will have the disorder?

Accepted Answer

$$1/2$$

Question 6

Which of the following scenarios is an example of incomplete dominance?

Accepted Answer

A pink-flowered plant results from crossing a red-flowered plant with a white-flowered plant.

Question 7

What is the result of nondisjunction during meiosis?

Accepted Answer

Some gametes have an extra or missing chromosome, leading to conditions such as Down syndrome.

Question 8

Which chromosomal mutation involves a segment of one chromosome attaching to a non-homologous chromosome?

Accepted Answer

Translocation

Question 9

Which of the following correctly describes the structure of a nucleotide in DNA?

Accepted Answer

A phosphate group, a deoxyribose sugar, and a nitrogenous base

Question 10

In DNA, what distinguishes the 3' end from the 5' end?

Accepted Answer

The 3' end has a free hydroxyl group ($$-OH$$), and the 5' end has a free phosphate group ($$-PO_4$).

Question 11

Why is DNA replication described as 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one parental and one newly synthesized strand.

Question 12

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Question 13

What is the main difference between the leading and lagging strands during DNA replication?

Accepted Answer

The leading strand is synthesized continuously, while the lagging strand is synthesized in short fragments.

Question 14

A man with genotype $$AaBb ($$where $$A$$ and $$B$$ are dominant alleles) produces sperm. According to the law of independent assortment, what is the probability that a sperm will carry both $$a$$ and $$b$$ alleles?

Accepted Answer

$$1/4$$

Question 15

Which of the following best describes the antiparallel nature of DNA?

Accepted Answer

One strand runs 5' to 3', and the other runs 3' to 5'.

Question 16

A child is born with three copies of chromosome 21. Which event most likely caused this condition?

Accepted Answer

Nondisjunction during meiosis

Question 17

Which enzyme joins Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

Ligase

Question 18

If a person with genotype $$I^A I^O ($$type A blood) has a child with a person with genotype $$I^B I^O ($$type B blood), what is the probability their child will have type O blood?

Accepted Answer

$$1/4$$

Question 19

Which of the following is true about homozygous dominant, heterozygous, and homozygous recessive genotypes?

Accepted Answer

Homozygous dominant and heterozygous genotypes always produce the same phenotype in complete dominance.

Question 20

Which enzyme synthesizes short RNA primers needed for DNA polymerase to begin replication?

Accepted Answer

Primase

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