Q: Which phase of the cell cycle is primarily responsible for the replication of DNA, and what is the correct formula for the number of DNA molecules present after this phase in a diploid cell with $$2n$$ chromosomes?

S phase; $$2 \times 2n$$ DNA molecules

Question 1

Which phase of the cell cycle is primarily responsible for the replication of DNA, and what is the correct formula for the number of DNA molecules present after this phase in a diploid cell with $$2n$$ chromosomes?

Accepted Answer

S phase; $$2 	imes 2n$$ DNA molecules

Question 2

During meiosis, crossing over occurs between homologous chromosomes. What is the evolutionary significance of this process?

Accepted Answer

It increases genetic variation among offspring

Question 3

A woman who is heterozygous for a recessive genetic disorder ($$Aa) $$and a man who is homozygous dominant ($$AA) $$have a child. What is the probability that their child will be a carrier of the disorder?

Accepted Answer

$$50\%$$

Question 4

Which of the following best describes the structure of DNA as discovered by Watson and Crick?

Accepted Answer

A double helix with complementary base pairing

Question 5

A genetic test reveals a mutation in the BRCA1 gene. What is the most likely consequence of this mutation?

Accepted Answer

Increased risk of breast and ovarian cancer

Question 6

Which biotechnology technique is used to amplify a specific segment of DNA, and what is the formula for the number of DNA copies after $$n$$ cycles?

Accepted Answer

Polymerase Chain Reaction (PCR); $$2^n$$ copies

Question 7

According to Darwin's theory of natural selection, which of the following is necessary for evolution to occur in a population?

Accepted Answer

Variation in traits must exist among individuals

Question 8

Which of the following best defines a species according to the biological species concept?

Accepted Answer

A group of organisms that can interbreed and produce fertile offspring

Question 9

If a mutation changes the codon $$UAC ($$tyrosine) to $$UAA ($$stop codon) in a gene, what type of mutation has occurred and what is its likely effect?

Accepted Answer

Nonsense mutation; premature termination of translation

Question 10

A plant with genotype $$RrYy ($$where $$R = $$round, $$r = $$wrinkled, $$Y = $$yellow, $$y = $$green) is crossed with another plant of genotype $$rryy. $$What is the expected phenotypic ratio in the offspring?

Accepted Answer

1 round yellow : 1 round green : 1 wrinkled yellow : 1 wrinkled green

Question 11

Which process is responsible for the independent assortment of genes during gamete formation?

Accepted Answer

Meiosis I

Question 12

A patient is found to have a point mutation in a gene that codes for an enzyme. Which of the following outcomes is most likely?

Accepted Answer

The mutation may have no effect, a minor effect, or a major effect depending on its location

Question 13

Which of the following is a direct result of nondisjunction during meiosis?

Accepted Answer

Gametes with abnormal numbers of chromosomes

Question 14

Which RNA molecule carries amino acids to the ribosome during translation?

Accepted Answer

tRNA

Question 15

In a population of beetles, a sudden environmental change favors green beetles over brown beetles. Over time, the frequency of the green allele increases. Which evolutionary mechanism is illustrated?

Accepted Answer

Natural selection

Question 16

Which of the following best describes the role of restriction enzymes in biotechnology?

Accepted Answer

They cut DNA at specific sequences

Question 17

If a cell starts with $$2n = 6$$ chromosomes, how many chromosomes will each daughter cell have after mitosis and after meiosis, respectively?

Accepted Answer

Mitosis: 6; Meiosis: 3

Question 18

Which of the following is NOT a requirement for Hardy-Weinberg equilibrium in a population?

Accepted Answer

Small population size

Question 19

A scientist uses gel electrophoresis to analyze DNA fragments. What property of DNA allows this technique to separate fragments?

Accepted Answer

DNA is negatively charged and moves toward the positive electrode

Question 20

Which of the following statements about evolution is most accurate?

Accepted Answer

Evolution is a change in allele frequencies in a population over time

General Biology Exam 2 Study Guide: Chromosomes, DNA, and Evolution

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