transcription and gene expression

Number of protein coding genes in human genome

Around 20,000

Why is the study of gene expression central in modern drug development

Most drugs cause long term effect through changes in gene expression contributing to both action of drugs and their side effects

Three steps in protein production

1. Regulation of transcription

2. Regulation of mRNA processing and decay

3. Regulation of translation

How can RNA fold into secondary and tertiary structures?

By internal base pairing

What conditions is RNA most unstable

Alkaline conditions

Why are ribose sugars less stable than deoxyribose

Have a hydroxyl group on 2 carbon so more prone to hydrolysis and chemical reactions

Role of promoter

Determines where the transcription start site

Found at upstream of gene which RNA polymerase binds to

Chromatin rearrangement

Open conformation and low nucleosome density permit RNA polymerase access

What structure do transcription factors have ?

Modular structure ( discrete inteconnected structures)

Gene

A section of DNA that directs transcription of one or more overlapping mature RNA molecules (mRNA , rRNA, tRNa)

Unit of transcription

How many codons are there out of the 64

61

How many stop codons are there within the 64

3

What is the start codon

AUG

stop codons examples

UAA

UAG

UGA

Coding region

A reading frame encoding a protein

What amino acid does AUG code for (start codon)

Methionine(Met )

Role of rRNA (Ribosomal)

Links the amino acid

Aminoacyl tRNA site

Where the aminoacyl tRNA recognises codon

P: peptidyle tRNA site

Peptidyl tRNA placement before Peptide formation

E

Where the uncharged tRNA exiting ribosome is located

3 main steps of protein synthesis

Initiation

Elongation

Termination

Initiation

Finding the start codon and assembling the ribosome with the first tRNAs

Elongation

Coupling amino acids from tRNAs to a growing peptide chain

Termination

Recognising the stop codon and releasing the new protein

Release factor

TRNA shaped protein that recognises the stop codon

Steps of translation elongation

1. Amainoacyl tRNA binding

2. Peptidyl transfer

3. Translocation

What is Peptidyl transfer catalysed by?

Ribosomal RNA

Replication

DNA synthesis by copying of existing DNA

Transcription

RNA synthesis by copying DNA

RNA processing

Modification of RNA in the nucleus and cytoplasm

Translation

Protein synthesis by decoding of RNA