Question 1

Which of the following best describes what occurs at the G$$_1$$ checkpoint in the cell cycle?

Accepted Answer

The cell checks for DNA damage and ensures sufficient resources are available for DNA replication.

Question 2

A mutation causes a cell to bypass the G$$_2$$ checkpoint. Which of the following is a likely consequence?

Accepted Answer

Cells may enter mitosis with damaged or incompletely replicated DNA.

Question 3

During which checkpoint does the cell verify that all chromosomes are properly attached to the spindle before proceeding with division?

Accepted Answer

M checkpoint

Question 4

Which of the following statements about DNA replication is correct?

Accepted Answer

DNA polymerase synthesizes new DNA in the 5' to 3' direction.

Question 5

A DNA molecule contains 35% adenine (A). According to Chargaff's rules, what percentage of guanine (G) would you expect?

Accepted Answer

$$15\%$$

Question 6

Why is a DNA helix with mostly A-T base pairs easier to separate than one with mostly G-C base pairs?

Accepted Answer

A-T pairs are held together by two hydrogen bonds, while G-C pairs have three.

Question 7

Which enzyme is responsible for joining Okazaki fragments on the lagging strand during DNA replication?

Accepted Answer

DNA ligase

Question 8

If a mutation changes the codon UGU to UGG in an mRNA sequence, what is the result?

Accepted Answer

A missense mutation that changes cysteine to tryptophan.

Question 9

Given the mRNA sequence 5'-AUG UGG GCU UGG-3', what is the corresponding amino acid sequence?

Accepted Answer

Met-Trp-Ala-Trp

Question 10

Which of the following best explains why some mutations do NOT alter the amino acid sequence of a protein?

Accepted Answer

The genetic code is redundant; multiple codons can specify the same amino acid.

Question 11

Which of the following is true about the relationship between DNA, mRNA, and protein?

Accepted Answer

DNA is transcribed into mRNA, which is then translated into protein.

Question 12

Which of the following would most likely result from a mutation that deletes a single nucleotide in the coding region of a gene?

Accepted Answer

A frameshift mutation that alters the reading frame of the gene.

Question 13

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

Eukaryotic mRNAs are processed with a 5' cap and poly(A) tail, while prokaryotic mRNAs are not.

Question 14

If the promoter region of a gene is mutated so that RNA polymerase cannot bind, what is the most likely outcome?

Accepted Answer

Transcription of the gene will not occur.

Question 15

Which of the following best describes the role of the poly(A) tail added to eukaryotic mRNAs?

Accepted Answer

It increases mRNA stability and facilitates export from the nucleus.

Question 16

Which strand of DNA is used as the template during transcription?

Accepted Answer

The template strand, which is complementary to the mRNA.

Question 17

Which of the following best explains why a mistake made during transcription is not considered a mutation?

Accepted Answer

Transcription errors are not permanent and do not alter the DNA sequence.

Question 18

Which of the following is a property of the genetic code that helps prevent some mutations from altering the amino acid sequence?

Accepted Answer

Redundancy (degeneracy) of the code

Question 19

If a codon in an mRNA sequence is changed from UGA to UGG, what is the effect on translation?

Accepted Answer

A stop codon is replaced by a codon for tryptophan, resulting in a longer protein.

Guided Study for Cell Cycle Checkpoints and Genetic Code Table

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