C1. It is a double-stranded structure that follows the AT/GC rule.
C2. Bidirectionality refers to the idea that two replication forks emanate from one origin of replication. There are four
DNA strands being made in two directions radiating outward from the origin.
C3. Statement C is not true. A new strand is always made from a preexisting template strand. Therefore, a double helix
always contains one strand that is older than the other.
TTGGHTGUTGG TTGGGTGTTGG CCAAACACCAA CCAAACACCAA
AACCCACAACC AACCCACAACC GGTTTGTGGTT HHUUTHUGHUU
C5. No. In a conservative mechanism, one double helix would always be fully methylated so the cell would not have
any way to delay the next round of DNA replication via a methylation mechanism.
C6. If we assume there are 4,600,000 bp of DNA, and that DNA replication is bidirectional at a rate of 750 nucleotides
If there were just a single replication fork:
4,600,000/750 = 6,133 seconds, or 102.2 minutes
Because replication is bidirectional: 102.2/2 = 51.1 minutes
Actually, this is an average value based on a variety of growth conditions. Under optimal growth conditions,
replication can occur substantially faster.
With regard to errors, if we assume an error rate of one mistake per 100,000,000 nucleotides:
= 4,600,000,000 nucleotides of replicated DNA
4,600,000,000/100,000,000 = 46 mistakes
When you think about it, this is pretty amazing. In this population, DNA polymerase would cause only 46 single
mistakes in a total of 1,000 bacteria, each containing 4.6 million bp of DNA.
C8. DNA polymerase would slide from right to left. The new strand would be
C9. 1. DnaA boxes—binding sites for the DnaA protein
2. Methylation sites—sites of adenine methylation that are important for regulating DNA replication
3. AT-rich region—site where the DNA initially denatures to form a replication bubble
C10. A. When looking at Figure 11.5, the first and third DnaA boxes are running in the same direction and the second
and fourth DnaA boxes are running in the opposite direction. Once you realize that, you can see that the sequences
are very similar to each other.
B. According to the direction of the first DnaA box, the consensus sequence is