DNA & RNATHEIR ROLE IN PROTEIN

SYNTHESIS

DNA – BASIC STRUCTURE

Polymer of nucleotides Deoxyribose

(5 carbon sugar) Phosphate group Nitrogen base

Adenine Guanine Thymine Cytosine

Hydrogen bonds Double helix - two

strands twisted

DNA – BASIC STRUCTURE

Sides – alternating sugar & phosphate grps

5’ end phosphate

3’ end sugar

Steps – base pairs Adenine – Thymine Cytosine – Guanine Connected by H-bonds

DNASTRUCTURE & FUNCTION

Blue prints for life Carries an

organisms genetic code

Carries instructions for making proteins: Immunology Metabolism Respiration Energy/Storage

Found in nucleus of cell

DNA - REPLICATION

Make a copy of DNA Occur prior to cell

division Steps:

Enzyme DNA polymerase unzips DNA

Two new “complimentary” strands built

RNA – BASIC STRUCTURE

Single strand Sugar – ribose Phosphate grp

Uracil replaces Thymine

3 Types Messenger (mRNA) Ribosomal (rRNA) Transfer (tRNA)

TRANSCRIPTION

Process used to make mRNA from DNA

Occurs in nucleus RNA polymerase

Enzyme splits DNA so RNA can form

Role of mRNA Carries directions

making protein to the ribosome

TRANSCRIPTION

Promoter Section DNA where

enzyme attaches TATA Box

Repeating sequence bases – signals where transcription should begin

Immediately followed by start codon AUG

TRANSCRIPTION

CODONS – Groups 3 bases code

for an amino acid AUG – “start” codon,

codes for methianine 64 different “3-letter”

codes for 20 different amino acids

Terminator – stop signals UGA, UAA, UAG

TRANSLATION Assembly of amino acids at the ribosome to

produce a protein Initiation – joining of mRNA, tRNA & ribosome

TRANSLATION

Elongation – the joining of amino acids tRNA bring A. acids

to ribosomes Anticodons on

tRNA match to codons on mRNA

Termination – production A. acid stops – no tRNA to match STOP codon

PROTEIN SYNTHESIS

PROTEIN SYNTHESIS

DNA TAC GCT AAG ACT MRNA

A. ACIDS

TRNA

POINT MUTATIONS Single base is changed – change in 1 a.

acid Silent (no change A.Acid) or result in

disease

FRAMESHIFT MUTATION

Insertion Addition of base

Deletion Removal of base

Both types result in change of entire amino acid sequence

Cytosine insertion on chrom. 16 believed cause Crohn’s disease