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DNA Replication
By: Brayden Woodrow
DNA Replication
DNA replication is the process where a copy of a DNA strand is made and the genetic information it contains is duplicated.
Step 1
An enzyme known as helicase enters at a adenine and thymine bond at a point known as the origin of replication. Helicase unwinds the double helix as it goes through the DNA strand. As helicase goes through the DNA strand, single stranded binding proteins cling to the sides of the strand to keep them together.
51
5131
31
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Helicase
Step 2
Another enzyme, polymerase III, enters the process. It reads from 31 to 51, but synthesizes the corresponding bonds from 51 to 31.
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III
Polymerase III then reads the parent strand and synthesizes the other bases.
Thymine
Cytosine
Thymine
Cytosine
Thymine
Cytosine
Adenine
Guanine
Adenine
Guanine
Adenine
Guanine Thymine
Cytosine
Adenine
Guanine
Thymine
Cytosine
Thymine
Cytosine
Thymine
Cytosine
Adenine
Guanine
Adenine
Guanine
Adenine
Guanine Thymine
Cytosine
Adenine
Guanine
Thymine
Cytosine
Thymine
Cytosine
Thymine
Cytosine
Adenine
Guanine
Adenine
Guanine
Adenine
Guanine Thymine
Cytosine
Adenine
Guanine
Step 3
DNA primase places an RNA primer from 51 to 31. The enzyme polymerase I changes that RNA primer into DNA. DNA ligase forms phosphodiester bonds. Adenine and thymine form a double bond and cytosine and guanine form a triple bond. When one of the purine bases bonds with a pyrimidine base, they form a quintuple (5) bond.
Results
After DNA replication takes place, you are left with two identical DNA strands.
Parent Strand Duplicate Strand
Purpose
Replication occurs so that the genetic material can be passed from the original cell to the daughter cell. This leads to the transfer of traits.
Meiosis
DNA Replication occurs in interphase. Interphase is the period between the division of two cells. During interphase, the cell increases in size and makes a copy of the cells’ DNA to prepare for the next division.
What are mutations?
A mutation is a permanent change in the DNA sequence that makes up genes. They differ in size from one DNA base to a large segment of chromosomes.
How do we get them?
Mutations can be inherited from a parent. In these cases, they are referred to as hereditary mutations. Once acquired, they are permanent throughout that person’s lifetime.
Mispairings
When a mispairing of bases occurs because of a shifting in the position of the nucleotides, it is called a wobble, one of a few different ways to form a mutation.
Insertions or Deletions
When a nucleotide is inserted or deleted at the wrong time or place, it creates another mutation. This process is known as strand slippage. A newly synthesized strand slightly loops out, which causes an addition of an extra nucleotide base. Sometimes, the template strand becomes slightly misplaced. This results in the deletion of nucleotide bases in the newly synthesized strand.
Telomeres
• A compound structure at the end of an eukaryotic chromosome
• Keep the ends of different chromosomes in the cell from attaching to each other
Okazaki Fragments
Short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication.
DNA Ligase
• A specific type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond
• Seals breaks in the phosphate-sugar backbone of DNA
Cancer
• Disease caused by an uncontrolled division of abnormal cells in a part of the body
• Telomerase causes cancer cells to divide and duplicate
Telomerase
• A ribonucleoprotein • Adds telomere sequence to the 31 end of DNA
strands• DNA polymerase then completes the synthesis
of the uncompleted ends of the other strand
