Cell Biology 6.1 – Flashcards

Consider the process that a cell uses to replicate its double-stranded DNA before undergoing cell division. Which statement describes the DNA in the resulting daughter cells?

Which term best describes DNA replication?

What kinds of bonds link the two strands of a double helix to each other?

DNA synthesis begins at:

Replication origins typically consist of a small stretch of duplex DNA that is relatively easy to pry apart. Which statement is true?

The two replication forks that form at an origin of replication move:

DNA synthesis proceeds:

Nucleotides are linked by:

The energy for DNA polymerization is provided by the hydrolysis of:

A newly synthesized DNA strand of a human chromosome:

Experimental evidence supporting the semiconservative nature of DNA replication came from:

A team of investigators is studying a virus that is believed to have a single replication origin in its genome, which consists of a small circle of double-stranded DNA. The researchers wonder whether, in this virus, replication proceeds in both directions from the origin, as it does in mammalian cells. Or perhaps replication proceeds only in one direction from the origin—eventually making its way around the circle. To find out, the investigators take a preparation containing multiple copies of the viral genome and allow the DNA to begin replicating. After a time, some molecules have been fully replicated, while others are only partway complete. That collection of replicated—and partially replicated—DNA is then exposed to a special type of nuclease that cuts through the DNA backbone at a single, specific site in the genome. This treatment converts the circular genomes into linear pieces of DNA. The researchers then examine these linear DNA molecules using an electron microscope. Examples of the molecules they see are shown in the diagram. Based on these observations, what is the most likely conclusion to be made about replication in this virus? https://s3.amazonaws.com/RM_Images/20160117001107403_raw.jpg

In a DNA double helix, which strand will serve as the template during replication?

In a classic experiment that's sometimes referred to as "the most beautiful experiment in biology," Matt Meselson and Frank Stahl tested the three models for DNA replication: the semiconservative model, the dispersive model, and the conservative model. The researchers started by incubating E. coli in a nutrient medium containing a heavy isotope of nitrogen, 15N. The bacteria incorporate this heavy isotope into their nitrogen-containing molecules, including DNA. DNA purified from these bacteria could be analyzed by a technique called equilibrium density centrifugation, which separates molecules on the basis of their density. Next, Meselson and Stahl took bacteria that had been growing in the heavy, 15N-containing nutrient medium and placed them in medium containing the lighter 14N isotope. The bacteria then began incorporating this light isotope into their DNA. After one round of replication, the researchers found that DNA purified from these bacteria was intermediate in density—halfway between the heavy, 15N-containing DNA and the light, 14N-containing DNA (as shown in the figure). From this observation alone, Meselson and Stahl could conclude that: https://s3.amazonaws.com/RM_Images/20160117001108903_raw.jpg

If DNA replication were conservative, what would Meselson and Stahl have seen following the first round of replication in E. coli that had been switched from a heavy, 15N-containing nutrient medium to a light, 14N-containing one?

If Meselson and Stahl had allowed their bacteria to undergo a second generation of growth in light medium, which of these distributions would they have seen? https://s3.amazonaws.com/RM_Images/20160117001111162_raw.jpg

The nucleotide sequence of one DNA strand in a DNA double helix is 5'-CATTGCCAGAAAAAT-3'. Which is the sequence of the complementary strand produced during replication?

When read in the same 5'-to-3' direction, the sequence of nucleotides in a newly synthesized DNA strand is the same as in the template strand used for its replication.

If an origin of replication is removed from a eukaryotic chromosome, the DNA on either side will also be lost as it cannot be replicated.