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Molecular Genetics

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DNA structure DNA is short for? DNA is short for? Deoxyribose Nucleic Acids Deoxyribose Nucleic Acids DNA is made up of 4 bases [Adenine (A), Guanine (G), Cytosine (C) and Thymine (T)], phosphates and sugars. DNA is made up of 4 bases [Adenine (A), Guanine (G), Cytosine (C) and Thymine (T)], phosphates and sugars. One base, phosphate and sugar is a nucleotide. One base, phosphate and sugar is a nucleotide.

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Deoxyribose Sugars Phosphate Connectivity: As always connect with Ts.As always connect with Ts. Cs always connect with Gs.Cs always connect with Gs. This is called a sugar phosphate backbone basesbasesbasesbases

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Whats our formation? DNA strands are generally found in this shape. DNA strands are generally found in this shape. The double helix The double helix Why- its all biochemistry Why- its all biochemistry All molecules want to be stable. All molecules want to be stable. All molecules are at rest when stable. All molecules are at rest when stable. To be at rest in this case, some weak To be at rest in this case, some weak bending is present (helix). bending is present (helix).

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Some new and some old Tell me what we are looking at. Tell me what we are looking at.

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Another look at how the histone does what it does New word: New word: A group of histones is called nucleosomes. A group of histones is called nucleosomes.

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How do we measure DNA length? We measure by base pairs We measure by base pairs Base pairs are important for what in Mendelian genetics? Base pairs are important for what in Mendelian genetics? A gene! A gene! Example: E. Coli- A bacteria Example: E. Coli- A bacteria 4,639,221 base pairs (ACGT) 4,639,221 base pairs (ACGT) 1.6 mm (millimeters) 1.6 mm (millimeters) The bacteria though is only 1.6 m (1/1000 the size) The bacteria though is only 1.6 m (1/1000 the size)

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Example: Humans Example: Humans 3 billion base pairs (ACGT) 3 billion base pairs (ACGT) 25,000 genes only 25,000 genes only Size is 10m Size is 10m

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Whats the coolest thing about DNA Its the universal code of the body- every cell has the same information. Its the universal code of the body- every cell has the same information. DNA is double-stranded. So, since there are rules to pairing, we can read one side and make a new copy to pair with it. DNA is double-stranded. So, since there are rules to pairing, we can read one side and make a new copy to pair with it. What does that mean? What does that mean? Replication Replication

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DNA replication What is the purpose? What is the purpose? To make another direct copy of DNA To make another direct copy of DNA How do we do it? How do we do it? Helicase- a protein that unravels and splits DNA strands Helicase- a protein that unravels and splits DNA strands DNA polymerase- a what? DNA polymerase- a what? Replication factors Replication factors DNA- the code of all codes DNA- the code of all codes Enzyme

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DNA Replication What part of the cell cycle does this happen? What part of the cell cycle does this happen? The S phase The S phase Why are we making another copy of DNA? Why are we making another copy of DNA? Why is DNA important in the first place? Why is DNA important in the first place? Example- Give me the recipe that Emeril would use to bake a German chocolate cake using only a computer.

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DNA Replication One set becomes two The original code serves as a template

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But Really Helicase Red= A Purple = T Blue= C Yellow= G 1. Helicase splits the two DNA strands. 2. Polymerase binds to the DNA. 3. Transcription factors bind into polymerase. 4. Polymerase moves along the DNA and compliments the old base 5. Polymerases can go both directions

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Where the two strands of DNA split is the replication fork. Where the two strands of DNA split is the replication fork. The two strands break their hydrogen bonds The two strands break their hydrogen bonds The new hydrogen bonds form with the new nucleic acids The new hydrogen bonds form with the new nucleic acids

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The amazing enzyme: DNA Polymerase It: Can act like a helicase sometimes Can act like a helicase sometimes Reads your DNA to match sides to compliment Reads your DNA to match sides to compliment Can read backwards once pairing is done Can read backwards once pairing is done Proofread Proofread

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Lets go over it one more time Helicase Red= A Purple = T Blue= C Yellow= G