1a) _____ is when the chemical bond linking a base to its nucleotide is broken.
ID: 141360 • Letter: 1
Question
1a) _____ is when the chemical bond linking a base to its nucleotide is broken.
a) Deamination b) Depurination c) Single stranded break d) Mismatch
1b) Which of the following is NOT used by stem cells to avoid mutations in their genome?
a) Infrequent replication of DNA b) Non-homologous recombination c) placement of stem cells in anatomically protected sites d) Apoptosis. e) MDR1(multidrug resistance-1) protein
1c) DNA polymerase can fix which of the following errors during DNA replication?
a) skipped base b)inserted base c) skipped dinucleotide d) inserted dinucleotide e) all of the above
Explanation / Answer
1a)The process in which the chemical bond between the base and it's nucleotide is broken is called depurination . This occurs in the deoxyribonucleotides , deoxyguanine , deoxyadenosine , in which the N-glycosilic bond between the base and the nucleotide is broken through hydrolysis. These releases the respective bases .
Deamination is the removal of amine group from a molecule .
Mismatch - erroneous insertions , deletions in the DNA or the RNA .
1b) Answer c) Placement of stem cells in antomically protected sites . This may not help the stem cells from the sudden changes in the genetic DNA .
1c) Answer d) inserted dinucleotide .
The main function of the DNA polymerase Is the making of a new strand on the single strand obtained from the parent DNA. This is in the 5'-3' direction .
While adding a new strand , it also functions as a proof reader , and checks for any mistakes in the new strand formed . If there is any mistake , or an incorrect coupling , the polymerase reverses it's direction by a base pair which is later excised .
The removed base pair is then replaced with the correct base pair by the DNA which then continues in the same direction .
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