Chapter 12, Problem 14A

Summary Introduction

To write:

A sentence defining a vocabulary term Okazaki fragments.

Introduction:

DNA stands for Deoxyribonucleic Acid. DNA is a polymer of nucleotides. Nucleotides are molecules composed of a sugar deoxyribose, with a phosphate group and a nitrogenous base attached to it. These nucleotides are attached to each other in strands through phosphodiester bonds to form a ‘sugar-phosphate backbone’. The bond formed is between the third carbon atom on the deoxyribose sugar of one nucleotide and the fifth carbon atom of another sugar on the next nucleotide.

Explanation of Solution

DNA replication a process by which DNA makes copies of itself.

DNA replication occurs in three stages namely, Initiation, Elongation, and Termination.

During DNA replication,one of the template strands of DNA is read in a 3’ to 5’ direction, which means that the new strand will be formed in a 5’ to 3’ direction. This newly formed strand is referred to as the Leading Strand. Only oneRNA primer is required to initiate DNA polymerase, during synthesis of leading strand as the process is occurring in a continuous manner. This is because DNA polymerase is able to extend the new DNA strand by reading the template 3' to 5', synthesizing in a 5' to 3' direction.

The other template strand or lagging strand is antiparallel, and is read in a 5’ to 3’ direction. As the helix unwinds, new RNA primers are added to the newly exposed bases on the lagging strand and DNA synthesis occurs in fragments,known as Okazaki fragments. The DNA synthesis of this strand also occurs in the 5' to 3' direction but many RNA primers are required during the synthesis of lagging strand.

The DNA synthesis of this strand also occurs in the 5' to 3' direction but many RNA primers are required during the synthesis of lagging strand. Once DNA synthesis has completed, it is important that the newly synthesized strands are bound and stabilized.  The Okazaki fragments are then joined by the enzyme DNA ligase.