Question

Ch 16: The Molecular Basis of Inheritance

Outline the process of DNA replication in a eukaryotic cell in at least 5 steps. Describe enzymes involved for each step and several different chemistry-based explanations for how the steps are performed.

Answer 1

Ans. Steps of DNA replication:

1). Unwinding of DNA double helix by helicase enzyme. This enzyme separates double strands of DNA and makes it single stranded.

2). Removal of supercoiling by the enzyme topoisomerase. It relieves supercoiling in DNA caused by opening of double strands.

3). Formation of primers by RNA polymerase enzyme. It makes a small nucleotide strand that provides free 3'-OH for DNA synthesis.

4). Polymerization of new strand by DNA polymerase enzyme. It adds nucleotides by making phosphodiester bonds between them, in new growing strand, complementary to the parent strand.

5). Ligation of okajaki fragements by ligase enzyme. Okajaki fragments are formed during lagging strand synthesis, which are latter joined together by ligase enzyme. It makes phosphodiaster bonds between two nucleotides.