DNA replication, the cell cycle and mitosis

Question 1

What two types of nucleotides are needed for DNA synthesis?

Answer 1

Oligonucleotide primer (RNA primer made by DNA primase) dNTPs (deoxynucleoside triphosphates)

Question 2

Explain how the lagging strand is synthesised.

Answer 2

DNA polymerase can only add dNTPs to the 3’ end of an oligonucleotide primer. The oligonucleotide primers attach and DNA polymerase moves in a 5’ to 3’direction adding the dNTPs to the growing chain. When the newly synthesised strand reaches the oligonucleotide primer of the previous okazaki fragment, the DNA polymerase is removed. Ribonuclease removes the RNA primer and Repair DNA polymerase replaces the RNA with DNA. DNA ligase then joins the adjacent okazaki fragments.

Question 3

Which three enzymes are involved in the joining of Okazaki fragments?

Answer 3

Ribonuclease, Repair DNA Polymerase, DNA ligase