Question

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

1. nuclease, DNA polymerase, DNA ligase
2. telomerase, primase, DNA polymerase
3. telomerase, helicase, single-stranded binding protein
4. DNA ligase, replication fork proteins, adenylyl cyclase

Short answer

1. The option “nuclease, DNA polymerase, DNA ligase” is true.
2. The option “telomerase, primase, DNA polymerase” is false.
3. The option “telomerase, helicase, single-stranded binding protein” is false.
4. The option “DNA ligase, replication fork proteins, adenylyl cyclase” is false.

Step-by-step solution

DNA synthesis

DNA synthesis is a complex mechanism in which there is a possibility of repair. The repair is fixed by DNA repair pathways to fix the damages in the DNA. Most of the repair process removes the damaged and replaces it with new sequences.

Explanation of option (A)

Nuclease is the enzyme that can cleave the DNA into segments. It can remove the uncommon base-pair hypoxanthine from the DNA segment, followed by DNA polymerase that can extend the sequence. DNA ligase can join nicks present in between the DNA fragments.

Thus, the sequence of nuclease, DNA polymerase, and DNA ligase can repair this kind of damage in the DNA.

Therefore, the given statement is true.

Explanation of option (B)

Telomeric repeats are added to the chromosomes that extend the telomeric ends of the chromosome. Primase is the enzyme that produces primers. DNA polymerase can elongate the DNA strand in the replication.

Thus, the sequence of telomerase, primase, and DNA polymerase can repair this kind of damage in the DNA. These enzymes cannot remove the hypoxanthine molecule and so cannot repair the DNA segment.

Therefore, the given statement is false.

Explanation of option (C)

Helicase is the enzyme that unwinds the DNA molecules to enter the process of DNA replication. Single-stranded binding proteins are the proteins that attach to DNA which is separated using helicase.

The proteins such as telomerase, helicase, and single-stranded binding proteins cannot repair the damage inDNA.

Therefore, the given statement is false.

Explanation of option (D)

Replication fork proteins are the proteins that assist the formation of the replication fork. The adenosine monophosphate is produced with the help of the enzyme adenylyl cyclase.

Thus, the sequence of DNA ligase, replication fork proteins, and adenylyl cyclase cannot repair this kind of damage.

Therefore, the given statement is false.