Question

Please describe briefly what might happen to each of the following prokaryotes or eukaryotes under the described conditions:

1. An E. coli strain exposed to UV light and then placed in the dark as compared to the same strain left in natural light.

2.   An yeast strain exposed to UV light and then placed in the dark  as compared to the same strain left in natural light.

3. An E. coli strain with a mutation in a gene that codes for a DNA glycosylase and makes it nonfunctional.

4. A null mutation in E. coli in the gene that codes for the enzyme dam methylase which methlates the A residue of the GATC consensus.

5. A null mutation in the gene that codes for DNA methyl transferase in yeast.

Answer 1

1.- UV light tends to cause DNA damage, thus leading to growth inhibition. The E. coli exposed to UV light will not grow as the control strain.

2.- It is the same case for yeast, they are sensitive to light so the exposed strain will die, there won't be yeast colonies in comparison to the control strain.

3.- DNA gycosylase is an important enzyme for the process of base excision repair, the lost of it will enable the bacteria to repair some DNA damage. This strain will be very vulnerable, they would die in conditions where wildtype strains can easily survive.

4.- Such methylation plays a major role in both DNA repairing and regulation of replication. The loss of such function would lead failure of correctly repair damage (vulnerable strain) and problems during replication that might lead to double replication.

5.- This enzyme has a major role in epigenetic regulation in yeast. This epigenetic modification prevents expression by condensin chromatine in the desired site. This strain will show abnormal genetic expression.