Objective: ◦ Describe the process of protein synthesis◦ Explain how a disruption in the sequence can

cause a change in appearance Journal:

◦ On the top of your note sheet, explain what DNA polymerase does in DNA replication.

The making of protein

RNA’s function is to take DNA’s code, copy it and use it to make proteins

Differs from DNA in that:◦ RNA is single stranded◦ Contains Ribose as sugar◦ Uracil instead of Thymine

U-A

Messenger RNA (mRNA)◦ Copies code from DNA and brings it to the

ribosome

Transfer RNA (tRNA)◦ Brings amino acids to ribosome to assemble

into protein

Transcription◦ Creates mRNA from code contained in a gene

(DNA)

Translation◦ mRNA code is read and “translated” into a string

of amino acids that make up a protein

RNA polymerase “unzips” DNA at a gene

mRNA is built by pairing A-U and C-G

When gene ends, mRNA breaks away from DNA and DNA zips back up

http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/transcription.swf

mRNA leaves the nucleus and heads to a ribosome

mRNA “letters” will be read in groups of 3 called codons

Each codon codes for 1 amino acid

mRNA binds to ribosome

tRNA brings over its amino acid

Next codon is read, next amino acid is brought over by another tRNA

Amino Acids bond together forming a protein

Process repeats until ribosome reaches a stop codon

Protein is released

http://www.columbia.edu/cu/biology/courses/c2005/images/animtransln.gif

TAC-AAA-GCT-TTT-CTA-CCG-ATC

Mutations: changes in DNA sequence

•Point Mutation: affect one nucleotide1. Substitutions – replace one of the nucleotides with another

- Can be lethal

TAC-AAG-GCT-TTT-CTA-CCG-ATC

TAC-AAC-GCT-TTT-CTA-CCG-ATC

OR

Frame shift mutations: Change the whole sequence by changing the order of how the sequence is read

- Insertion or deletion– add or remove a nucleotide

TAC-AAA-GCT-TTT-CTA-CCG-ATC

TAC-AAA-GCT-TTT-CTA-CCG-ATC

TAC-AAA-GCT-TGT-TCT-ACC-GAT-C

TAC-AAA-GCT-TTC-TAC-CGA-TC

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