Question 1

Who provided X-ray diffraction photographs of purified DNA fibers that suggested a helical structure with a consistent diameter of about 2 nm and a complete helical turn every 3.4 nm?

Accepted Answer

A) Hershey and Chase 
B) Chargaff 
C) Franklin 
D) Watson and Crick

Question 2

The chemical bond connecting one nucleotide with the next along one strand of a DNA molecule is called a

Accepted Answer

A) glycosidic bond. 
B) hydrogen bond. 
C) phosphate bond. 
D) phosphodiester bond.

Question 3

In 1952, Hershey and Chase confirmed Avery's (1944) conclusion that

Accepted Answer

A) proteins are the repositories for hereditary information. 
B) DNA is the repository for hereditary information. 
C) RNA is the repository for hereditary information. 
D) each DNA molecule is composed of two strands that are twisted into a double helix.

Question 4

Endonucleases and exonucleases are enzymes that can remove nucleotides from a polynucleotide chain.An endonuclease removes nucleotides _______ while an exonuclease removes nucleotides _____________.

Accepted Answer

A) from the 5' end of the chain; from the 3' end of the chain 
B) from the 3' end of the chain; from the 5' end of the chain 
C) internally; from the ends of the chain 
D) from the ends of the chain; internally

Question 5

If a short sequence of DNA is 5' AATTGCCGT 3', its complement is

Accepted Answer

A) 5' AAAACGCCA 3'. 
B) 3' TTAACGGCT 5'. 
C) 3' TTAACGGCA 5'. 
D) 3' TTAAGCCGA 5'.

Question 6

Information obtained by Franklin from X-ray crystallography on DNA suggested that it is shaped like a

Accepted Answer

A) helix. 
B) ribbon. 
C) hollow cylinder. 
D) pleated sheet.

Question 7

Who demonstrated that phage genetic material is DNA and not protein?

Accepted Answer

A) Hershey and Chase 
B) Chargaff 
C) Franklin 
D) Watson and Crick

Question 8

The method of DNA replication, where each original strand is used as a template to build a new strand, is called the

Accepted Answer

A) conservative method. 
B) semiconservative method. 
C) disruptive method. 
D) continuous method.

Question 9

As the two strands of DNA are unraveled, which enzyme relieves the strain on the two strands?

Accepted Answer

A) DNA polymerase 
B) DNA ligase 
C) DNA gyrase 
D) DNA endonuclease

Question 10

You decide to repeat the Meselson-Stahl experiment, except this time you plan to grow the cells on light 14N medium for many generations and then transfer them to heavy 15N medium and allow them to grow for 2 additional generations (2 rounds of DNA replication).If the semiconservative model of DNA replication is correct, what is the expected distribution of DNA in the density gradient after two rounds of replication?

Accepted Answer

A) One band of intermediate density. 
B) One band of intermediate density and one band of light density. 
C) One band of intermediate density and one band of heavy density. 
D) One band of heavy density and one band of light density.

Question 11

I think the proactive stance is a better attitude to promote than after-the-fact worrying! When planning a long week of sunbathing on the beach, What type of DNA damage should sunbathers be aware of before hitting the beach?

Accepted Answer

A) photolyase-induced mutations 
B) decreased telomere length 
C) thymine dimers 
D) activation of uvr A, B, and C genes

Question 12

If 14% of the nucleotides from a DNA molecule contain the base T, what percent will contain the base G?

Accepted Answer

A) 14% 
B) 18% 
C) 28% 
D) 36%

Question 13

Watson and Crick developed a model of DNA in which the two strands twist into the shape of a ________________.

Accepted Answer

A) circle 
B) helix 
C) double helix 
D) double pleated sheet

Question 14

Xeroderma pigmentosum (XP) is a rare autosomal recessive disorder.Patients with XP exhibit a cellular hypersensitivity to ultraviolet (UV) radiation, a high incidence of skin cancer and premature aging.Based on these clinical characteristics, what is the most likely cause for this disease?

Accepted Answer

A) defects in DNA repair 
B) defects in DNA replication 
C) lack of telomerase activity 
D) shortened telomeres

Question 15

If we think of the DNA double helix as a twisted ladder, what makes up the rungs or steps of the ladder?

Accepted Answer

A) phosphate groups only 
B) alternating phosphate groups and sugars 
C) sugars only 
D) purines and pyrimidines

Question 16

In DNA, a purine must always pair with a pyrimidine and vice versa in order to ensure that

Accepted Answer

A) the distance between the two phosphodiester backbones remains constant. 
B) the two strands are antiparallel. 
C) the distance between one base pair and the next remains constant. 
D) each base pair is held together by three hydrogen bonds.

Question 17

___ is the genetic material for all cellular organisms and some viruses.

Accepted Answer

A) RNA 
B) DNA 
C) Protein 
D) Chromatin

Question 18

In Griffith's experiments,

Accepted Answer

A) mice infected with live nonvirulent bacteria developed pneumonia and died. 
B) nonvirulent bacteria transformed the virulent bacteria into a nonvirulent variety. 
C) mice infected with heat-killed virulent bacteria and live nonvirulent bacteria developed pneumonia and died. 
D) mice infected with heat-killed virulent bacteria and heat-killed nonvirulent bacteria developed pneumonia and died.

Question 19

You are asked to give a classroom demonstration of DNA supercoiling.To do so, you take two different colored pieces of rubber tubing, twist them very tightly and excessively around each other and join the ends of the tubing appropriately.Next, you relieve the supercoiling by breaking one strand and unwinding it.In this demonstration, the breaking and unwinding to relieve the supercoiling simulates the action of

Accepted Answer

A) exonucleases. 
B) polymerases. 
C) ligases. 
D) topoisomerases.

Exam 14: Dna: the Genetic Material