Question 1

Which of the following best describes the structure of a DNA nucleotide?

Accepted Answer

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

Question 2

Which part of a DNA nucleotide varies among different nucleotides?

Accepted Answer

The nitrogenous base

Question 3

The phosphodiester backbone of DNA is formed by covalent bonds between which components of adjacent nucleotides?

Accepted Answer

The 3’ hydroxyl group of one deoxyribose and the 5’ phosphate group of the next

Question 4

Hydrogen bonds in the DNA double helix are responsible for which of the following?

Accepted Answer

Holding complementary nitrogenous bases together between the two strands

Question 5

If one strand of DNA has the sequence 5’-ATGCCGTA-3’, what is the sequence of the complementary strand (written 5’ to 3’)?

Accepted Answer

5’-TACGGCAT-3’

Question 6

Which of the following statements about the antiparallel arrangement of DNA strands is correct?

Accepted Answer

One strand runs 5’ to 3’ and the other runs 3’ to 5’

Question 7

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

Accepted Answer

Helicase

Question 8

Which enzyme synthesizes short RNA primers needed to initiate DNA synthesis on both the leading and lagging strands?

Accepted Answer

Primase

Question 9

Okazaki fragments are:

Accepted Answer

Short DNA fragments synthesized on the lagging strand during DNA replication

Question 10

Which enzyme is responsible for joining Okazaki fragments together during DNA replication?

Accepted Answer

DNA ligase

Question 11

A mutation causes DNA polymerase III to lose its 3’ to 5’ exonuclease activity. What is the most likely consequence?

Accepted Answer

Increased errors in DNA replication due to loss of proofreading

Question 12

Which of the following best explains why DNA synthesis occurs in the 5’ to 3’ direction?

Accepted Answer

DNA polymerase can only add nucleotides to the 3’ hydroxyl group of the growing strand

Question 13

Which enzyme relieves the tension ahead of the replication fork caused by unwinding of the DNA double helix?

Accepted Answer

Topoisomerase

Question 14

During DNA replication, which enzyme removes RNA primers and replaces them with DNA nucleotides?

Accepted Answer

DNA polymerase I

Question 15

A patient is found to have a genetic disorder in which their DNA ligase is nonfunctional. Which of the following would most likely occur during DNA replication?

Accepted Answer

Okazaki fragments would remain unjoined on the lagging strand

Question 16

Which of the following is the correct order of enzyme action at a replication fork on the lagging strand?

Accepted Answer

Helicase, primase, DNA polymerase III, DNA polymerase I, ligase

Question 17

If a DNA molecule is composed of 30% adenine, what percentage of guanine would you expect to find?

Accepted Answer

$$20\%$$

Question 18

A scientist is analyzing a DNA fragment and finds that it has a 5’ phosphate group at one end and a 3’ hydroxyl group at the other. Which statement best describes the directionality of this DNA fragment?

Accepted Answer

It runs from 5’ to 3’

Question 19

Which of the following best describes the relationship between Okazaki fragments and RNA primers?

Accepted Answer

Each Okazaki fragment begins with an RNA primer synthesized by primase

Question 20

A researcher is studying a new drug that inhibits the activity of single-strand binding proteins (SSBs) during DNA replication. What is the most likely effect of this drug?

Accepted Answer

The separated DNA strands would re-anneal, preventing replication

DNA Structure and Replication: Molecular Genetics Study Notes

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