Deck 9: DNA: The Chemical Nature of the Gene

Question 1

The genetic material must be capable of carrying large amounts of information, replicating faithfully, and translating its coding instructions into phenotypes.
-Why was the discovery of the structure of DNA so important for understanding genetics?

Answer 1

Without knowledge of the structure of DNA, an understanding of how genetic information was encoded or expressed was impossible.

Question 2

Details of the structure of DNA were worked out by a number of scientists. At first, DNA was interpreted as being too regular in structure to carry genetic information but, by the 1940s, DNA from different organisms was shown to vary in its base composition.

-Levene made which contribution of our understanding of DNA structure?

A) Determined that the nucleus contains DNA.
B) Determined that DNA contains four nitrogenous bases.
C) Determined that DNA consists of nucleotides.
D) Determined that the nucleotide bases of DNA are present in regular ratios.

Answer 2

Determined that DNA consists of nucleotides.

Question 3

The process of transformation indicates that some substance-the transforming principle-is capable of genetically altering bacteria. Avery, MacLeod, and McCarty demonstrated that the transforming principle is DNA, providing the first evidence that DNA is the genetic material.

-If Avery, MacLeod, and McCarty had found that samples of heat-killed bacteria treated with RNase and DNase transformed bacteria, but samples treated with protease did not, what conclusion would they have made?

A) Protease carries out transformation.
B) RNA and DNA are the genetic materials.
C) Protein is the genetic material.
D) RNase and DNase are necessary for transformation.

Answer 3

Protein is the genetic material.

Question 4

Using radioactive isotopes, Hershey and Chase traced the movement of DNA and protein during phage infection. They demonstrated that DNA, not protein, enters the bacterial cell during phage reproduction and that only DNA is passed on to progeny phages.
-Could Hershey and Chase have used a radioactive isotope of carbon instead of ³²P? Why or why not?

Question 5

By collecting existing information about the chemistry of DNA and building molecular models, Watson and Crick were able to discover the three-dimensional structure of the DNA molecule.

-What did Watson and Crick use to help solve the structure of DNA?

A) X-ray diffraction.
B) Laws of structural chemistry
C) Models of DNA
D) All the above

Question 6

The primary structure of DNA consists of a string of nucleotides. Each nucleotide consists of a five-carbon sugar, a phosphate, and a base. There are two types of DNA bases: purines (adenine and guanine) and pyrimidines (thymine and cytosine).

-How do the sugars of RNA and DNA differ?

A) RNA has a six-carbon sugar; DNA has a five-carbon sugar.
B) The sugar of RNA has a hydroxyl group that is not found in the sugar of DNA.
C) RNA contains uracil; DNA contains thymine.
D) DNA's sugar has a phosphorus atom; RNA's sugar does not.

Question 7

DNA consists of two polynucleotide strands. The sugar-phosphate groups of each polynucleotide strand are on the outside of the molecule, and the bases are in the interior. Hydrogen bonding joins the bases of the two strands: guanine pairs with cytosine, and adenine pairs with thymine. The two polynucleotide strands of a DNA molecule are complementary and antiparallel

-The antiparallel nature of DNA refers to

A) its charged phosphate groups.
B) the pairing of bases on one strand with bases on the other strand.
C) the formation of hydrogen bonds between bases from opposite strands.
D) the opposite direction of the two strands of nucleotides.

Question 8

DNA can assume different secondary structures, depending on the conditions in which it is placed and on its base sequence. B-DNA is thought to be the most common configuration in the cell.
-How does Z-DNA differ from B-DNA?

Question 9

In DNA and RNA, base pairing between nucleotides on the same strand produces special secondary structures such as hairpins.

-Hairpins are formed in DNA as a result of

A) sequences on the same strand that are inverted and complementary.
B) sequences on the opposite strand that are complements.
C) sequences on the same strand that are identical.
D) sequences on the opposite strand that are identical.