Methylation is involved in controlling the timing of DNA replication in E. coli.
ID: 52904 • Letter: M
Question
Methylation is involved in controlling the timing of DNA replication in E. coli. Describe how SeqA binding and timing of replication is affected in a loss-of-function Dam Methylaase mutant (no Dam methyalase present)
1. Describe the methylation state when SeqA binds to DNA.
2. How would SeqA binding be affected in a loss-of-function Dam Methylaase
mutant.
3. How would timing of DNA replication be affected.
You have discovered two different mutations in yeast. Regarding what you know about how the timing of eukaryotic DNA replication is controlled, provide an explanation for the following phenotypes.
Mutant 1: You find evidence of DNA replication during G1 phase.
RecA/Rad 51 has important roles in repairing double-stranded breaks.
1. What type of mechanism is RecA/Rad51 used in during double-stranded break repair.
2. Why was it important to use the Hfr bacterial strains to identify the RecA proteins.
Explanation / Answer
1.
As a result of DNA replication, the Methylation state in the E.Coli genome changes from fully methylated to hemimethylated
2.
SeqA binds to the origin of replication, sequestering it and thus preventing methylation
3.
Timing of DNA replication increases.
1.
RecA/Rad51 is Homologous Recombination mechanism used in during double-stranded break repair
2.
Hfr bacterial strains are used to identify the RecA proteins because of Single strand annealing which requires two complementary single strands two find one another whose identification is done by Hfr bacterial cells i.e the RecA proteins