Question 1

Why is RNA required for DNA replication?

Accepted Answer

DNA polymerase can only add nucleotides to an existing chain. This chain is provided by a small RNA molecule called a primer. Without RNA primers, DNA polymerase would not be able to initiate replication because there would be no existing chain to add to. Therefore, RNA is required for DNA replication.

Question 2

Which of these is true of RNA?

Accepted Answer

RNA can form double helices, although they are typically shorter and less stable than DNA double helices.

Question 3

What radiolabelled substance did Hershey and Chase use to label the protein component of the bacteriophage in their study to determine whether protein or DNA was necessary for phage production?

Accepted Answer

Hershey and Chase used sulfur to label the protein component of the bacteriophage because sulfur is found in proteins (specifically in the amino acids cysteine and methionine) but not in DNA. This allowed them to trace the fate of the proteins during the infection process.

Question 4

Pyrimidines are a nitrogenous base containing a double ring,while purines contain a single ring.

Accepted Answer

Pyrimidines contain a single ring, while purines contain a double ring.

Question 5

By applying an equation formulated by Shannon,the information content of a polymer such as DNA or protein depends on its:

Accepted Answer

The information content of a polymer like DNA or protein, according to Shannon's equation, depends on both the number of discrete monomers (e.g., the number of different bases or amino acids) and the total number of monomers in the polymer. This is because the variety of monomers and their quantity together determine the complexity and potential information encoded in the sequence.

Question 6

A phosphodiester bond joins one nucleotide to another in the DNA polymer.

Accepted Answer

A phosphodiester bond is formed between the phosphate group of one nucleotide and the sugar (deoxyribose) of another nucleotide, resulting in the formation of a sugar-phosphate backbone in DNA.

Question 7

The step in DNA replication in which two replication forks moving in opposite directions may meet is called

Accepted Answer

The meeting of two replication forks moving in opposite directions indicates the completion of DNA replication, which is referred to as termination. Initiation refers to the beginning of DNA replication, elongation refers to the extension of the new DNA strands, translation refers to the process of protein synthesis, and translocation refers to the movement of molecules across a biological membrane.

Question 8

Hershey and Chase relied on ________ to physically separate the infected bacterial cells from the phage ghosts.

Accepted Answer

Hershey and Chase relied on centrifugation to physically separate the infected bacterial cells from the phage ghosts.

Question 9

If 35% of the bases in a region of the mouse genome are cytosine,what percentage in that region are adenine?

Accepted Answer

In double-stranded DNA, the percentage of adenine equals the percentage of thymine, and the percentage of cytosine equals the percentage of guanine. Therefore, if 35% of the bases in a region of the mouse genome are cytosine, then 35% of the bases in that region are guanine, and 100% - 35% - 35% = 30% of the bases in that region are adenine.

Question 10

Prokaryotes have a circular chromosome surrounded by a nuclear membrane.

Accepted Answer

Prokaryotes do not have a nuclear membrane, so their circular chromosome is not surrounded by one. Rather, their DNA is located in a region called the nucleoid.

Question 11

Transformation in bacteria results from the uptake of foreign DNA.

Accepted Answer

Transformation is a process in which bacteria take up foreign DNA from their surroundings and incorporate it into their genome, resulting in genetic transformation.

Question 12

The energy for DNA synthesis comes most directly from

Accepted Answer

The energy for DNA synthesis comes from the nucleoside triphosphates (dNTPs), which are used as substrates for the DNA polymerase enzyme. As each nucleotide is added to the growing DNA strand, two of the phosphate groups are cleaved off, releasing energy that is used to drive the polymerization reaction. The released phosphates combine to form inorganic pyrophosphate (PPi), which is hydrolyzed by pyrophosphatase to provide additional energy for the reaction. However, it is the dNTPs themselves that provide the primary source of energy for DNA synthesis. The other choices (deoxyribose, NADH, and ribose) are components of nucleotides or other cellular molecules, but they are not directly involved in providing energy for DNA synthesis.

Question 13

Which of the following is not true of naturally occurring DNA?

Accepted Answer

Naturally occurring DNA contains deoxyribose sugar, not ribose sugar.

Question 14

The protein that progressively unwinds DNA ahead of each replication fork is called

Accepted Answer

Helicase is the protein that unwinds DNA ahead of each replication fork.

Question 15

How many replication forks depart from an origin of replication?

Accepted Answer

Two replication forks depart from an origin of replication, moving in opposite directions and creating a replication bubble.

Question 16

The complementary sequence of 5' AATTCGCTTA 3' is

Accepted Answer

The answer of The complementary sequence of 5' AATTCGCTTA 3'...

Question 17

Who demonstrated that DNA,rather than protein,was the genetic material of bacteria?

Accepted Answer

Avery demonstrated in 1944 that DNA, rather than protein, was the genetic material of bacteria by conducting experiments with Streptococcus pneumoniae.

Question 18

Meselson and Stahl relied on equilibrium density gradient centrifugation in a _______ solution to resolve the DNA containing ¹⁴N from the DNA containing ¹⁵N.

Accepted Answer

Meselson and Stahl used cesium chloride (CsCl) solution for equilibrium density gradient centrifugation because CsCl forms a density gradient and DNA band can be visualized by staining with ethidium bromide. This allows for separation of the different densities of the DNA containing ¹⁴N from the DNA containing ¹⁵N.

Question 19

Which of the following is not involved in ensuring the accuracy of a cell's genetic information?

Accepted Answer

Transformation is not involved in ensuring the accuracy of a cell's genetic information. Redundancy, repair enzymes, precision of replication machinery, and DNA polymerase proofreading mechanism all play important roles in ensuring accurate replication and transmission of genetic information. However, transformation refers to the uptake of DNA from the environment by a bacterial cell, and is not directly related to maintaining the accuracy of the cell's existing genetic information.

Question 20

If chromosomal DNA were single stranded,which of the following would be most reduced compared to a double stranded molecule?

Accepted Answer

Informational fidelity, or the consistency of sequence between generations, would be most reduced if chromosomal DNA were single-stranded. Double-stranded DNA allows for complementary base pairing, which is crucial for error-checking and repair mechanisms that maintain sequence accuracy across generations. Single-stranded DNA lacks this complementary strand, making it more prone to mutations and errors during replication.

Quiz 4: Linkage, Recombination, and the Mapping of Genes on Chromosomes