Question 1

What catalyzes the formation of phosphodiester bonds between a DNA strand and a new nucleotide being added during DNA replication?

Accepted Answer

DNA polymerase is the enzyme responsible for catalyzing the formation of phosphodiester bonds between the 3' end of a DNA strand and the 5' phosphate of a new nucleotide, thus facilitating DNA replication.

Question 2

Which of the following types of cells are affected most by telomere shortening?

Accepted Answer

Eukaryotic cells are most affected by telomere shortening because they have linear chromosomes where telomeres are located. Prokaryotic cells typically have circular DNA and thus do not have telomeres. Telomere shortening is a concern in both plant and animal cells, which are subcategories of eukaryotic cells.

Question 3

Which of the following is most likely to result from reduced or very little active telomerase activity?

Accepted Answer

Telomerase activity is crucial for maintaining telomere length. Reduced or very little active telomerase activity leads to the shortening of telomeres, which is associated with cellular aging and the loss of cell function.

Question 4

Telomere shortening puts a limit on the number of times a cell can divide. Research has shown that telomerase can extend the life span of cultured human cells. Which of the following best explains the effect of telomerase on cellular aging?

Accepted Answer

Telomerase adds repetitive nucleotide sequences to the ends of chromosomes, thereby counteracting the shortening of telomeres that occurs with each cell division. This action can slow or delay the cellular aging process by extending the replicative capacity of cells.

Question 5

Researchers found a strain of bacteria that had mutation rates one hundred times higher than normal. Which of the following statements correctly describes the most likely cause of these results?

Accepted Answer

The proofreading mechanism of DNA polymerase is crucial for correcting errors during DNA replication. If it is not working properly, the mutation rate would significantly increase, as the enzyme would fail to correct errors that occur as DNA is copied.

Question 6

In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect?

Accepted Answer

Primase synthesizes RNA primers necessary for both leading and lagging strand DNA synthesis. A mutation in primase would impair the initiation of DNA replication on both strands.

Question 7

In a healthy eukaryotic cell, the rate of DNA repair is typically equal to the rate of DNA mutation. Which of the following is most likely to result if the rate of repair lags behind the rate of mutation?

Accepted Answer

When the rate of DNA repair lags behind the rate of mutation, it increases the likelihood of mutations accumulating within the cell's genome. These mutations can lead to uncontrolled cell growth and division, characteristics of cancerous cells.

Question 8

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

Accepted Answer

The leading strand is synthesized continuously in the 5'→ 3' direction because it follows the direction of the replication fork. The lagging strand is synthesized in short segments, known as Okazaki fragments, also in the 5'→ 3' direction, but in a discontinuous manner due to the replication fork moving away from it.

Question 9

In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules?

Accepted Answer

The base-pairing rules in DNA state that adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). Therefore, the total amount of A and T will be equal to the total amount of C and G, making option B correct.

Question 10

Which of the following structural characteristics is most critical for the association between histones and DNA?

Accepted Answer

Histones are positively charged due to the presence of basic amino acids like lysine and arginine. This positive charge allows them to bind tightly to the negatively charged phosphate backbone of DNA, facilitating the formation of nucleosomes and the packaging of DNA into chromatin.

Question 11

Histone proteins contain internal cores that are hydrophobic and surface amino acids that are positively charged. Which of the following characteristics of DNA would best support tight binding between DNA and histones?

Accepted Answer

The answer of Histone proteins contain internal cores that are...

Question 12

In his work with pneumonia-causing bacteria and mice, Griffith found that ________.

Accepted Answer

Griffith's experiment demonstrated that a substance from dead pathogenic bacteria could transform live nonpathogenic bacteria into a pathogenic form. This transformation suggested that the genetic material could be transferred between bacteria, leading to the discovery of DNA as the material of heredity.

Question 13

Which of the following statements correctly describes the structure of chromatin?

Accepted Answer

Heterochromatin is indeed highly condensed and typically transcriptionally inactive, making it appear darker under a microscope, while euchromatin is less compact, allowing for easier access by the transcription machinery, and is where most active transcription takes place.

Question 14

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

Accepted Answer

DNA polymerase adds nucleotides only to the 3' end of a growing strand, and because the two strands of DNA are antiparallel, this necessitates different processes for synthesizing the leading and lagging strands.

Question 15

Which of the following statements accurately describes the structure of a eukaryotic chromosome?

Accepted Answer

Eukaryotic chromosomes are composed of a single linear molecule of double-stranded DNA associated with proteins, including histones, which help in packaging the DNA into a compact, organized structure.

Question 16

Which of the following lists represents the order of increasingly higher levels of organization of chromatin?

Accepted Answer

The correct order of chromatin organization from lower to higher levels is nucleosome, 30-nm chromatin fiber, and then looped domain. Nucleosomes are the basic unit of DNA packaging, consisting of DNA wrapped around histone proteins. These nucleosomes are further packed into the more compact 30-nm chromatin fiber, which in turn is organized into higher order structures such as looped domains.

Question 17

What are telomeres?

Accepted Answer

Telomeres are the protective caps at the ends of linear chromosomes, which help prevent the loss of genetic information during cell division and protect the chromosomes from degradation.

Question 18

Use the figure to answer the following question.  Referring to the figure, what bases will be added as DNA replication proceeds on the bottom strand?

Accepted Answer

The answer of Use the figure to answer the following...

Question 19

Which of the following is most likely to result if a cell is unable to produce histone proteins?

Accepted Answer

Histone proteins are crucial for the packaging of DNA into chromatin, allowing it to fit within the nucleus. Without histones, DNA cannot be efficiently packed, leading to issues with its containment within the nucleus.

Question 20

The lagging strand is characterized by a series of short segments of DNA (Okazaki fragments) that are joined together to form a finished lagging strand. The experiments that led to the discovery of Okazaki fragments gave evidence for which of the following ideas?

Accepted Answer

The discovery of Okazaki fragments supported the idea that DNA polymerase synthesizes DNA in only one direction (5' to 3'), necessitating the production of short DNA segments on the lagging strand, which are later joined together.

Quiz 16: Nucleic Acids and Inheritance