BSC2010 Chapter 9

Suppose the results of the Hershey-Chase experiment had turned out differently than they did. A hypothetical set of data that might have resulted is shown in the table. The + symbol indicates one unit of radioactivity and the – symbol indicates a lack of radioactivity above the normal background levels. Which of the following conclusions fits these data?

Genetic information is contained in protein

Which aspect of the biology of viruses was crucial in enabling Hershey and Chase to use the experimental design described in the tutorial for deducing the chemical nature of genetic material?

Viruses insert only part of their bodies through the host membrane during infection

How would both the results of the Hershey-Chase experiment and conclusions drawn have been different if the viral DNA had been associated with proteins that were transmitted along with the DNA during infection of the bacterial host cells?

The bacterial pellet would have contained both isotopes, making it unclear which substance was the genetic material

In the Hershey-Chase experiment, which radioisotopes were used to label which biomolecules that make up a virus?

32P in nucleic acids; 35S in proteins

If adenine makes up 20 percent of the bases in a sample of double-stranded DNA, what percentage of the bases would be uracil?

0

The 5′ end of the DNA growing strand during DNA replication

is the part of the strand that is added first

A point mutation

is a change in a single nucleotide of DNA

A silent mutation

would likely not affect the activity of a protein

Which statement about DNA structure is false?

The 3′ end is phosphorylated

Which type of mutations involves changes in single nucleotides within a chromosome?

Point mutations

In order to show that DNA in cell extracts is the genetic material responsible for genetic transformation of bacteria, important corroborating evidence should indicate that _____ did not affect transforming activity

enzymes that hydrolyzed proteins

Mutations

can arise from errors in DNA replication

In multicellular organisms

somatic mutations may be passed to daughter cells by mitosis

If guanine makes up 20 percent of the bases in a sample of double-stranded DNA, what percentage of the bases would be cytosine?

20

The polymerase chain reaction requires

cyclical denaturation and binding of double-stranded DNA

Which chemical will not cause an induced mutation?

Salt (NaCl)

The replication of lagging strands of DNA differs from the replication of leading strands in that

DNA synthesis proceeds in the 3′ to 5′ direction

Which deoxyribonucleoside triphosphate is not used for DNA synthesis?

dUTP

Which statement about repairing errors in DNA replication is false?

DNA helicase repairs the remaining nicks in the newly replicated strand

If adenine makes up 20 percent of the bases in a sample of double-stranded DNA, what percentage of the bases would be cytosine?

30

In many eukaryotes, there are repetitive sequences at the ends of chromosomes called telomeres. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.

lagging; telomerase

A mutant strain of yeast grows well at 20C, but not at 37C, whereas the wild-type strain grows well at both temperatures. The mutation is an example of a ______ mutation

Conditional

Which mechanism causes induced mutations to occur?

A mutagen causing a permanent change in DNA sequence

A-T base pairs in a DNA double helix

are chemically distinct from G-C base pairs

Ligases are enzymes that link two DNA fragments together. Suppose a bacterium develops a mutation in the ligase gene needed for DNA replication. This mutation results in an inactive form of the enzyme. What outcome can you expect for this bacterium and why?

The bacterium will not be able to replicate itself because only one DNA strand will result from the replication process instead of two.

How does synthesis of the leading strand differ from synthesis of the lagging strand during DNA replication?

More primers are needed per lagging strand synthesized than are needed per leading strand synthesized.

Which of the following is a reason that explains why DNA replication occurs in a continuous fashion on one parental DNA strand and in a discontinuous fashion on the other parental DNA strand?

DNA polymerase only works to add nucleotides in one direction of the growing chain.

Okazaki fragments become incorporated into which component of the DNA replication complex?

Lagging strand