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Transcript of DNA
Structure and Replication
Kate Cam Natasha
DNA is a long, double stranded bundle of genetic information. It controls all the cell's activities by storing the information for synthesis of proteins.
DNA is located with in the nucleus of the cell, and can be found tightly coiled and compacted into chromosomes around proteins.
Every human cell has 46 chromosomes.
If the DNA from one cell was placed end to end it would be around 2m in length.
*The average Male is 1.80m
*The average female is 1.65m
This is an image of the diffraction pattern, discovered and photographed by Rosalind Franklin.
Watson and Crick are the scientists most commonly accredited with ground breaking discoveries regarding DNA. They were the first to publish on the its double helix structure. However, they used other scientists' findings and research to publish their papers, and very little of their own. Regardless, they were given the credit for DNA's structure.
Watson and Crick were awarded the Nobel Prize for Physiology of Medicine in 1962. Rosalind could not be considered because she died before the prize was awarded.
Rosalind Franklin was a British, Physical Chemist. She used x-rays to discover that Watson and Crick's hypothesis that DNA existed in a triple helix structure was incorrect. Rosalind Franklin was not credited for her discovery because Watson and Crick were the first to publish on the structure.
Rosalind Franklin shared her knowledge and findings opening with other scientists, but her picture of the diffraction pattern was shown to Watson and Crick without her permission.
STRUCTURE of DNA
DNA is shaped in a double helix
3 main components:
The Backbone of DNA
The backbone of DNA is made up of alternating sugar and phosphate groups.
The sugar specific to DNA is deoxyribose
The nitrogen bases bond to the deoxyribose.
The oxygen points in the direction of the 5' end (3' to 5').
The two backbones oppose in direction.
Recombinant DNA is a strand of DNA that has genetic material from more than one source. The DNA is taken from two different sources and fused together.
There are 4 different types:
Complimentary Base Pairs
Create bacteria that are able to metabolize oil and can assist in cleaning up oil spills
Creating drought and pesticide resistant crops
Production of insulin and growth hormones
Create proteins which can prevent and cure diseases such as sickle cell anemia and cystic fibrosis
Hydrogen bonds 3
Hydrogen bond 2
Plasmid rings are extracted from bacteria and sliced into segments by enzymes
DNA from another source is inserted to the plasmid segment which now will contain recombinant (recombined) DNA
When the plasmid carrying the recombinant DNA enters the bacteria again, the bacteria will have the ability to make a protein it was originally unable to
HOW IT WORKS
In the Human Body
She died at a young age from ovarian cancer. It is thought that her career with x-rays and radiation lead to her early death.
A helicase unwinds the DNA from its helix structure and begins to break the hydrogen bonds that hold together the complimentary base pairs. The DNA unzips and the two backbones begin to separate.
One backbone is called the 'leading strand' while the other is called the 'lagging strand'.
Polymerase is able to continuously read the leading strand, however the lagging strand is different because the 3' and 5' end are opposite.
When copying the lagging strand the polymerases must detach and reconnect during the process. This leaves disconnected fragment of the DNA called,
The Okazaki fragments are connected by DNA ligase. The ligase connects and seals the sugar-phosphate backbone onto the DNA.
Each cell contains a complete set of DNA. This creates the need for DNA to replicate when parental cells divide to create two new daughter cells.
Polymerase attach to each strand and read the parental DNA. This enzyme then finds and attaches the complementary base.
Polymerase are only able to read from the 3' end to the 5'.
After DNA replication is complete the cell is left with two complete sets of 'daughter DNA'. It is now able to continue the process of mitosis.