GENE 2000 - mRNA processing and translation

Three types of mRNA processing

1.addition of 5' cap

2.intron removal and exon splicing

3.3' polyadenylation

Functions of the 5' cap

1. protect 5' end from degradation

2. allows mRNA to move from nucleus to cytoplasm

3. binds to small ribosomal subunit in the cytoplasm

Mechanism of intron removal and exon splicing

snurps bind to introns splice sites at the ends of introns in pre-mRNA and brings the ends together to cut them out and splice exons

the function of exon splicing is to produce

polypeptides with correct amino acid sequences

3' polyadenylation description

-200 A's join 3' end via poly A polymerase to protect from degradation and buy time

poly A tail is degraded by

exonucleases

Translation is the process by which

ribosomes uses mRNA to synthesize polypeptides with tRNA

Prokaryotic ribosomes are

30S and 50S, together, 70S

Eukaryotic ribosomes are

40S and 60S, together 80S

An adapter molecule is aka

tRNA

The 3' end of the tRNA molecule binds to

AA

tRNA have an

anticodon

The genetic code has __ letter words

3; 4^3=64 codes

3/64 codons are

stop codons

What is the wobble hypothesis

H bonding at the 3rd position of the codon is less strict

The initial methionine is usually later

removed

subunits joins at the

start codon

ribosomal tRNA sites

A (aminoacyl) = arrival

P site (peptidyl) = growing

E = exit

Energy from the hydrolysis of GTP is bound to

transcription factors

Four stages of termination

1. stop codon

2.release factor protein binds to A site and polypep is released

3.AA chain processed to a protein

4. ribosome units separate