M4 Flashcards
What is meant by the description “antiparallel” regarding the strands that make up DNA?
The 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand.
After mixing a heat-killed, phosphorescent strain of bacteria with a living nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?
Descendants of the living cells are also phosphorescent.
In his work with pneumonia-causing bacteria and mice, Griffith found that:
some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.
DNA is synthesized in which of the following directions?
In the 5’ > 3’ direction on both DNA strands.
When a DNA molecule is described as replicating bidirectionally, that means that it has two:
Replication forks.
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive adenine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
In E. coli, there is a mutation in a gene called dnaB that compromises the helicase activity. Which of the following would you expect as a result of this mutation?
No replication fork will be formed.
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?
Gaps left at the 5’ end of the lagging strand
At replication forks:
RNA primers are synthesized by primase.
An Okazaki fragment has which of the following arrangements?
5’ RNA nucleotides, DNA nucleotides 3’
The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that:
the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.
The leading and the lagging strands differ in that:
the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
How can the leading and lagging strands be synthesized in a coordinated fashion?
DNA Polymerase works as a dimer, and the looped lagging strand allows the enzyme to proceed in the same direction with each strand.
What is the function of topoisomerase?
Relieving strain in the DNA ahead of the replication fork
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won’t this experiment work?
Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
