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4.1 describe the process of DNA replication and explain its significance
describe the process of DNA replication and explain its significance
The process
- Recall from Blueprint of Life, Subsection 3, that DNA is a double-stranded molecule twisted into a helix with each strand comprised of a sugar-phosphate backbone and attached bases – adenine (A), thymine (T), cytosine (C) and guanine (G) – connected to a complementary strand by pairing the bases, A-T and G-C.
- A unit made up of a deoxyribose sugar, a phosphate molecule and one of four nitrogen bases (adenine, thymine, guanine and cytosine) is called a nucleotide. Thus, DNA consists of nucleotide units. The nitrogen bases that are part of each nucleotide are the rungs of the double helix of DNA. They only combine in one way, adenine binds to thymine and guanine binds to cytosine.
- Along the DNA molecule, there are long sequences of genetic code made up of these bases. The replication of these long sequences accounts for the replication of the genetic code of an organism.
- The process of DNA replication consists of the following steps.
Step 1: |
The DNA double helix is unwound by an enzyme. |
Step 2: |
The DNA unzips forming two single strands |
Step 3: |
Nucleotides are added to the single strands resulting in two identical strands of DNA |
The two double stranded molecules are the chromatids.
The significance
- The significance of this process is the genetic information is passed on from generation to generation. During sexual reproduction, the genetic code is copied and then half of the genetic information passes into each of the sex cells (ovum or sperm). When fertilisation occurs the new organism has half the genetic material from each parent.
- The DNA in a cell contains the genetic information to make an entire organism. When a cell divides it takes with it an exact copy of the genetic code of that organism.
To see an animation of this process go to the site below.
DNA Workshop
PBS Online, the site of the Corporation for Public Broadcasting, USA.