The following are True/False Questions: 1. Recombination can still take place in

Question

The following are True/False Questions:

1. Recombination can still take place in a RecB- strain of E. coli

2.The UAG stop codon causes the ribosome to terminate translation in an "amber nonsense suppressor" background

3. XerCD is ALWAYS involved in separating chromosomes once they have replicated

4. A RecA- strain of E. coli is competent for artificial transformation of pUC18

5. A DNA photolyase mutant is MORE SENSITIVE to UV damage than wild type cells if cells are only grown under daylight conditions

Explanation / Answer

1) FALSE

Recombination occurs due to the complex of three protein RecB, RecC and RecD acting together on the DNA segments. So, only  RecB- strain of E. coli do not show recombination.

2) TRUE

In E.Coli wobble rules amber suppressing tRNAs can only read UAG codons, but ochre-suppressing tRNAs can read both UAA and UAG codons.

3) FALSE

Topoisomerase IV removes replication links wheras XerCD remove links introduced during homologous recombination and replication as well.

4) TRUE

RecA protect along with DprA incoming foreign ssDNA undergoing for recombination hence transformation.

5) TRUE

In arabidopsis it is shown that DNA in particular strongly absorbs UV-B; therefore, it is the most important target for UV-B induced damage. A DNA photolyase mutant is MORE SENSITIVE to UV-B damage than wild type cells if cells are only grown under daylight conditions.

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