Question 1

Which of the following best describes what DNA genes actually encode for, according to the central dogma of biology?

Accepted Answer

Polypeptides

Question 2

During transcription in a eukaryotic cell, which of the following sequences correctly describes the flow of genetic information and the cellular location where this process occurs?

Accepted Answer

DNA to mRNA in the nucleus

Question 3

A double-stranded DNA molecule has the following orientation:

$$3' \longrightarrow 5' ($$top strand)
$$5' \longrightarrow 3' ($$bottom strand)

Which strand serves as the template for mRNA synthesis, and in which direction is the new mRNA synthesized?

Accepted Answer

The top strand is the template; mRNA is synthesized 5' to 3'

Question 4

If an mRNA molecule contains 12 nucleotides, what is the maximum number of amino acids that could be present in the translated polypeptide?

Accepted Answer

4

Question 5

The genetic code is described as 'redundant but not ambiguous.' What does this mean?

Accepted Answer

More than one codon can specify the same amino acid, but each codon specifies only one amino acid.

Question 6

Which of the following statements about start and stop codons is correct?

Accepted Answer

The start codon signals where translation begins, while stop codons signal where translation ends.

Question 7

A scientist wants to amplify a specific segment of DNA in the lab. Which technique should they use, and what are the three main steps involved?

Accepted Answer

Polymerase Chain Reaction (PCR); denaturation, annealing, extension

Question 8

During DNA replication, which enzyme is responsible for unwinding the DNA double helix at the replication fork?

Accepted Answer

Helicase

Question 9

Why are RNA primers necessary during DNA replication?

Accepted Answer

DNA polymerases can only add nucleotides to an existing strand with a free 3' OH group.

Question 10

Which of the following best explains why DNA synthesis is continuous on the leading strand but discontinuous on the lagging strand?

Accepted Answer

DNA polymerase can only synthesize DNA in the 5' to 3' direction, so the lagging strand is made in short fragments away from the replication fork.

Question 11

In eukaryotic cells, why do chromosomes become shorter after each round of DNA replication, and what role do telomeres play?

Accepted Answer

The ends of linear chromosomes cannot be fully replicated, so telomeres protect coding DNA from loss.

Question 12

Which of the following best describes the difference between the genome and the proteome of a cell?

Accepted Answer

The genome is all the DNA in a cell, while the proteome is all the proteins expressed by the cell.

Question 13

Which of the following statements about genetically modified organisms (GMOs) is correct?

Accepted Answer

GMOs contain genes from another species, made possible because the genetic code is universal.

Question 14

Which of the following enzymes removes RNA primers and replaces them with DNA during DNA replication?

Accepted Answer

DNA polymerase I

Question 15

A muscle cell and a nerve cell in the same human body have the same DNA. What primarily accounts for their differences in structure and function?

Accepted Answer

They express different sets of proteins due to differences in mRNA transcription.

Question 16

Which of the following best describes the function of DNA ligase during DNA replication?

Accepted Answer

It joins Okazaki fragments together on the lagging strand.

Question 17

During PCR, why are fewer enzymes required compared to DNA replication in a living cell?

Accepted Answer

PCR uses heat to separate DNA strands instead of helicase and SSBPs.

Question 18

Which of the following is the correct order of events during DNA replication at a replication fork?

Accepted Answer

Helicase unwinds DNA, primase synthesizes RNA primer, DNA polymerase III extends DNA, DNA polymerase I replaces primer, DNA ligase seals fragments.

Question 19

A mutation causes a change in a single nucleotide of a gene, resulting in a codon that still specifies the same amino acid. What is this type of mutation called, and why does it occur?

Accepted Answer

Silent mutation; because the genetic code is redundant

Central Dogma, DNA Replication, and PCR: Study Guide for BIOL 208

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