Question

Please help with these quesitons thanks!!!

1. why are the strans of a DNA molecule said to be complementary?

2. what steps are in eukaryotic DNA replication?

3. what enzyme joins individual nucleotides to produce the new strand of DNA?

4. what are the 3 components in DNA replication that require ATP?

Answer 1

Ans. 1. Because (according to Chargaff’s rule) adenine (A) always pairs with thymine (T) and guanine (G) always pairs with cytosine (C), the base pairing is complementary. During DNA replication of one strand (template strand), the bases are added being added onto the newly synthesized strand are complementary to the template strand. Therefore, the both the strands- the template strand and the newly synthesized strand through it, in the resultant DNA molecule are also complementary. Therefore, the whole DNA is said to be complementary.

Ans. b. The steps of DNA replication in eukaryotes are-

Initiation- The DNA melts at multiple origin of replications. Primase enzyme synthesizes RNA primer on both the template strands.

Elongation- The replisome (DNA polymerase holoenzyme associated with replication fork on DNA) polymerizes new DNA strands and elongate them.

Termination- Replication terminates at certain DNA sequences (Ter sites) or when replisomes from opposite direction collide together.   

Ans. c. DNA polymerases (In eukaryotes- pol e replicates leading strand; pol d replicates lagging strand) join two individual nucleotides to produce new DNA strand.

And. d. Components of DNA replication requiring ATP

Dna A protein (have ATPase activity) hydrolyzes ATP to melt the DNA at origin of replication.

Dna B helicase loading onto the lagging strands requires ATP.

DNA gyrase requires ATP to removes negative supercoils originating during advancement of the replication fork.