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DNA Replication

What is it?When is it done?What is copied?

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Two New, Two New, Identical Identical

DNA DNA Strands Strands Result Result from from

ReplicatiReplicati

onon

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PROTEIN PROTEIN SYNTHESISSYNTHESIS

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Protein Synthesis• After replication and cell division, each

new cell has its own DNA

• Now, how do those cells use that DNA to make proteins?

• How do you go from DNA (nucleic acid) to protein (amino acid)?

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Overview of Protein Synthesis

• Copy (mRNA) is made of gene

• mRNA sent out of nucleus

• Ribosomes use mRNA as instructions to make a protein

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Protein SynthesisProtein Synthesis

Two phases: Two phases: DNADNA

Transcription Transcription

mRNAmRNA

Translation Translation

proteinprotein

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TranscriptiTranscriptionon

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TranscriptionTranscription In nucleusIn nucleus

DNA the template for DNA the template for mRNAmRNA

RNA polymeraseRNA polymerase makes makes the mRNAthe mRNA

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Only one DNA strand is used

Just a portion of the DNA is copied (one gene)

copy is called mRNA

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RNA Differs from DNARNA Differs from DNA

DNA RNADeoxyribose

sugarRibose sugar

Double stranded

Single stranded

T (thymine) U (uracil)

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Question:Question:

What would be the What would be the complementary RNA complementary RNA strand for the following strand for the following DNA sequence?DNA sequence?

DNA 5’-DNA 5’-GCGTATGGCGTATG-3’-3’

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Answer:Answer:

•DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’•RNA 3’-CGCAUAC-5RNA 3’-CGCAUAC-5’’

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TranslatioTranslationn

mRNA mRNA protein protein

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TranslationTranslation

ribosome

Ribosome reads the mRNA and makes protein

mRNA

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• mRNA leaves nucleus

• ribosome attaches to mRNA

• ribosome reads the bases in groups of 3 (codon)

AUG CUG

codon

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The ribosome uses the code to make the protein

How?

How do you go from nucleic acid to amino acid?

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tRNAtRNA

• Carries amino Carries amino acids to acids to ribosomeribosome

• Has Has anticodonsanticodons that are that are complementacomplementary to ry to mRNA mRNA codonscodons

U A C

Amino acid

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AUG CUG

UAC

A A

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Genetic CodeGenetic Code DNA contains a DNA contains a triplet codetriplet code

Every three bases on DNA Every three bases on DNA stands for stands for ONE amino acidONE amino acid

Codon: Codon: Each group of 3 bases Each group of 3 bases on on mRNAmRNA

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r

• http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302

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Mutations

1. Gene Mutations

2. Chromosome Mutations

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What happens when there is a mistake during replication?

• What could go wrong when the DNA is being replicated?

• http://www.pbs.org/wgbh/nova/genome/program.html

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Gene Mutations

1. Point Mutations

A. Substitution

2. Frame shift MutationsA. Insertion

B. Deletion

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Point Mutations – substitution

One WRONG BASE is used

Original The fat cat ate the wee rat.Mutation The fat hat ate the wee rat

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Examples of Point Mutations

• Sickle Cell Anemia

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Examples of Point Mutations

• Tay Sachs Hemophilia B

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Frame Shift Mutations

A

• Insertion AAT AGG CAG GTT

• Deletion AAT AGG CAG GTT

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Frame Shift Mutations A

• Insertion AAT AGG CAG GTT

becomes AAT AAG GCA GGT …

• Deletion AAT AGG CAG GTT

becomes AAA GGC AGG …

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Frame Shift

• Original The fat cat ate the wee rat.

• Insertion The fat caa tet hew eer at.

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Example of Frame Shift Mutation:

Huntington’s Disease

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Chromosome Mutations

1. Inversions

2. Duplications

3. Deletions

4. Translocations

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Incorrect Chromosome Number –

from nondisjunction during meiosis

• Trisomy 21 causes Down’s Syndrome

• http://learn.genetics.utah.edu/units/disorders/whataregd/down/