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DNA Structure and Function. What is DNA?. DeoxyriboNucleic Acid DNA is a Nucleic Acid The main job of DNA is to make PROTEINS. What is the function of DNA?. It is your genetic material or “program.” Passed from cell to cell. DNA can give clues to ancient mysteries!. - PowerPoint PPT Presentation
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DNA Structure and Function
What is DNA?
DeoxyriboNucleic Acid
DNA is a Nucleic Acid The main job of DNA
is to make PROTEINS.
What is the function of DNA?
It is your genetic material or “program.”
Passed from cell to cell.
DNA can give clues to ancient mysteries!
Where do you find DNA?
DNA is found in the nucleus of the cell.
Our genes are on our chromosomes.
Chromosomes are made up of a chemical called DNA.
“Building Blocks” of DNA
Each nucleotide consists ofDeoxyribose (5-carbon sugar) Phosphate groupA nitrogen-containing base (A, G, T, C)
Nucleotide Structure
CH2
O
CC
C C
Sugar(deoxyribose)
NNitrogenous base (A, G, C, or T)
O=P-O O
Phosphate Group
Nitrogen Bases
Adenine (A)
Guanine (G)
Thymine (T)
Cytosine (C)
A or G
T or C
DNA Structure Watson-Crick Model
DNA is also called: The Double Helix Strands are held together by hydrogen bonds
between bases
Bases: A matches with T and C matches with G The sides of the ladder are a sugar-phosphate
backbone, while the “rungs” of the ladder are the bases.
DNA is a double strand
The four bases of DNA are:
Adenine (A) Guanine (G) Thymine (T) Cytosine (C)
Make a copy of the following DNA Sequence:
DNA(Original): A T C G C G A A T C C A G
Copy: T A G C G C T T A G G T C
Base-Pairing Rule
DNA replication
Before mitosis and meiosis, all of the DNA in the cell must be copied or replicated
How does this happen?
newnew old old
DNA Replication Half of the
replicated DNA strand is “old” and the other half is “new”
Basepairing During Replication
• Each old strand serves as a template for the new complementary strand
DNA Replication: Fast & Accurate!
It takes E. coli <1 hour to copy 5 million base pairs in its single chromosome & divide to form 2 identical daughter cells
Human cell copies its 6 billion bases & divide into daughter cells in only few hours
Remarkably accurateonly ~1 error per 100 million bases~30 errors per cell cycle
DNA Repair
Mistakes can occur during replication Proofreading enzymes correct any
mistakes that occur during replication. DNA studies have helped us solve major
problems in history and in health. Ex. The Czar’s family in Russia, crime
scene investigation, and paternity tests.