Molecular Molecular GeneticsGenetics

DNA structureDNA structureDNA is short for?DNA is short for?

DDeoxyribose eoxyribose NNucleic ucleic AAcidscidsDNA is made up of 4 bases [Adenine (A), DNA is made up of 4 bases [Adenine (A),

Guanine (G), Cytosine (C) and Thymine Guanine (G), Cytosine (C) and Thymine (T)], phosphates and sugars.(T)], phosphates and sugars.

One base, phosphate and sugar is a One base, phosphate and sugar is a nucleotide.nucleotide.

Deoxyribose“Deoxyribose“Sugars”Sugars”

PhosphatePhosphate

Connectivity:Connectivity:

•““A”s always connect with “T”s.A”s always connect with “T”s.

•““C”s always connect with “G”s.C”s always connect with “G”s.

This is called a sugar phosphate backboneThis is called a sugar phosphate backbone

bbaasseess

What’s our formation?What’s our formation?

DNA strands are generally found in this DNA strands are generally found in this shape.shape.The double helixThe double helix

Why- it’s all Why- it’s all biochemistrybiochemistryAll 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 weakTo be at rest in this case, some weak

bending is present (helix).bending is present (helix).

Some new and some oldSome new and some old

Tell me what we are looking at.Tell me what we are looking at.

Another look at how the histone Another look at how the histone does what it doesdoes what it does

New word:New word:A group of histones is called A group of histones is called nucleosomes.nucleosomes.

How do we measure DNA length?How do we measure DNA length?

We measure by base pairsWe measure by base pairsBase pairs are important for what in Base pairs are important for what in

Mendelian genetics?Mendelian genetics?A gene!A gene!

Example: E. Coli- A bacteriaExample: E. Coli- A bacteria4,639,221 base pairs (ACGT)4,639,221 base pairs (ACGT)1.6 mm (millimeters)1.6 mm (millimeters)The bacteria though is only 1.6 µm (1/1000 The bacteria though is only 1.6 µm (1/1000

the size)the size)

Example: HumansExample: Humans3 billion base pairs (ACGT)3 billion base pairs (ACGT)25,000 genes only25,000 genes onlySize is 10µmSize is 10µm

What’s the coolest thing about DNAWhat’s the coolest thing about DNA

It’s the universal code of the body- every It’s the universal code of the body- every cell has the same information.cell has the same information.

DNA is double-stranded. So, since there DNA is double-stranded. So, since there are rules to pairing, we can read one side are rules to pairing, we can read one side and make a new copy to pair with it.and make a new copy to pair with it.

What does that mean?What does that mean?ReplicationReplication

DNA replicationDNA replication

What is the purpose?What is the purpose?To make another direct copy of DNATo make another direct copy of DNA

How do we do it?How do we do it?Helicase- a protein that unravels and splits Helicase- a protein that unravels and splits

DNA strandsDNA strandsDNA polymerase- a what? DNA polymerase- a what? Replication factorsReplication factorsDNA- the code of all codesDNA- the code of all codes

EnzymeEnzyme

DNA ReplicationDNA Replication

What part of the cell cycle does this What part of the cell cycle does this happen?happen?The S phaseThe 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-Example- Give me the recipe that Give me the recipe that Emeril would use to bake a German Emeril would use to bake a German chocolate cake using only a computer.chocolate cake using only a computer.

DNA ReplicationDNA ReplicationOne set

becomes two

The original code

serves as a template

But ReallyBut Really

Helicase

Red= ARed= A

Purple = TPurple = T

Blue= CBlue= C

Yellow= GYellow= 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

Where the two strands of DNA split is the Where the two strands of DNA split is the replication fork.replication fork.

The two strands break their hydrogen The two strands break their hydrogen bondsbonds

The new hydrogen bonds form with the The new hydrogen bonds form with the new nucleic acidsnew nucleic acids

The amazing enzyme: DNA The amazing enzyme: DNA PolymerasePolymerase

It:It:Can act like a helicase sometimesCan act like a helicase sometimesReads your DNA to match sides to Reads your DNA to match sides to

complimentcomplimentCan read backwards once pairing is doneCan read backwards once pairing is done

ProofreadProofread

Let’s go over it one more timeLet’s go over it one more time

Helicase

Red= A Red= A Purple = TPurple = T

Blue= C Blue= C Yellow= GYellow= G