Question 1

Which of the following best explains why sexual reproduction leads to greater genetic variation in offspring compared to asexual reproduction?

Accepted Answer

Sexual reproduction combines genetic material from two parents, allowing for independent assortment and crossing over during meiosis.

Question 2

A human cell with 46 chromosomes undergoes meiosis. How many chromosomes will each resulting gamete contain, and what is this condition called?

Accepted Answer

23 chromosomes; haploid ($$n)$$

Question 3

During which phase of meiosis do homologous chromosomes separate, and what is the significance of this event?

Accepted Answer

Anaphase I; it reduces the chromosome number by half, ensuring genetic diversity.

Question 4

Which of the following is NOT one of the three main factors that contribute to genetic diversity in sexually reproducing organisms?

Accepted Answer

Replication of DNA during S phase

Question 5

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

Accepted Answer

3 tall : 1 short

Question 6

Which of Mendel’s laws states that two alleles for a heritable character separate during gamete formation and end up in different gametes?

Accepted Answer

Law of segregation

Question 7

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

Accepted Answer

$$50\%$$

Question 8

Which of the following best describes the difference between linked genes and unlinked genes?

Accepted Answer

Linked genes are inherited together because they are located close to each other on the same chromosome.

Question 9

A cell undergoes nondisjunction during meiosis II. Which of the following could result from this event?

Accepted Answer

Some gametes will have an extra chromosome (n+1), some will have one less (n-1), and some will be normal.

Question 10

Which of the following is a pyrimidine found in DNA?

Accepted Answer

Thymine

Question 11

Which enzyme is responsible for adding nucleotides to the growing DNA strand during replication?

Accepted Answer

DNA polymerase

Question 12

If a DNA strand has the sequence $$5'	ext{-}ATCGGTA-3'$$, what is the complementary sequence?

Accepted Answer

$$3'	ext{-}TAGCCAT-5'$$

Question 13

Which of the following statements about semiconservative replication is correct?

Accepted Answer

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

Question 14

A patient is diagnosed with Down syndrome, which is caused by trisomy 21. Which chromosomal event most likely led to this condition?

Accepted Answer

Nondisjunction during meiosis

Question 15

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA is usually double-stranded, while RNA is usually single-stranded.

Question 16

In a dihybrid cross between two heterozygous pea plants ($$YyRr 	imes YyRr$$), what is the expected phenotypic ratio in the F2 generation?

Accepted Answer

9:3:3:1

Question 17

Which of the following scenarios best illustrates the concept of hemizygosity?

Accepted Answer

A male has only one allele for an X-linked gene.

Question 18

Which of the following changes to chromosome structure involves a segment of a chromosome being reversed end to end?

Accepted Answer

Inversion

Question 19

During DNA replication, which strand is synthesized discontinuously, and what are the short fragments called?

Accepted Answer

Lagging strand; Okazaki fragments

Question 20

A geneticist is studying a trait controlled by a single gene with two alleles. If the dominant allele is not expressed in the phenotype of a heterozygote, which inheritance pattern is most likely?

Accepted Answer

Incomplete dominance

Biology Exam 4 Review: Meiosis, Mendelian Genetics, Chromosomes & Inheritance, DNA Structure & Replication

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