Question

In order for a cell to move past the G2 checkpoint and into M phase, the cell has to check for which of the following? A All of the DNA has been replicated B. All of the DNA damage has been repaired c. All of the chromosomes are attached to the mitotic spindle D. A and B only E. All of the above (A, B, and C)

Answer 1

Answer 1) The G2 checkpoint exists before the M phase. It checks for DNA damage as well as DNA replication. If the DNA has incorrect replication it will pause at the G2 phase and allow for repair. If the repair is unable to be complete it results in the cell entering the apoptosis pathway of programmed cell death.

Thus the answer is C) A and B only.

Answer 2) Deamination is the loss of ammonia by a hydrolysis reaction resulting in the conversion of a cytosine into a uracil this often occurs spontaneously. This is a replacement of the base, not a loss.

When depurination occurs with DNA, it leads to the formation of apurinic site and results in an alteration of the structure. This results in information loss in the form of bass loss.

Thymine dimers are formed by the dimerization of to pyrimidine molecules. This results in the formation of molecular lesions. This is not a type of base loss.

Insertion is addition of a base in the genome. This is not a type of base loss.

Thus the answer here is B) Depurination.

Answer 3) DNA ligase is the enzyme used to join fragments of DNA together. Thus the answer is A) Ligase.