Question

Biochemestry Write down a review article on: - “Regulation of gene expression”

➢ With special emphasis on the following elements:

1. Levels of regulation of gene expression

2. Difference between constitutive and regulated genes

3. Regulation of gene expression at the level of transcription

4. The regulatory mechanisms at level of posttranscriptional processing of mRNA

5. Epigenetic mechanisms for control of gene expression

Answer 1

1)Levels of regulation of gene expression includes:

• Chromatin domains
• Transcription
• Post transcriptional modification
• RNA transport
• Translation
• mRNA degradation

2) i)constitutive genes :

• This genes are required all time by the cells, i.e, gene are always on.
• This gene are called as house keeping genes and are expressed always.
• These are required to maintain the cellular function.

    ii)Regulated genes:

• This genes are expressed only under certain conditions to save cell energy
• It controls the expression of genes
• Regulator genes codes for repressor and activator proteins.

3)Regulationof gene expression at the level of transcription:

Coversion of DNA to RNA is called Transcription

It controls the rate of transcription and production of number of RNa

Transcription of the gene by RNA polymerase can be regulated by several mechanisms

• Specificitry factors –Alters the specificity of RNA polymerase
• Transcription factors – Position RNA polymerase and release them to transcribe mRNA
• Repressors – Binds to operators
• Activators – Improves interaction between RNA polymerase and the promotor
• Enhancers – loops the DNA
• Silencers – silences the gene expression

Process:

· RNA polymerase and transcription factors binds to the promoter region

· Transcription bubble is formed and DNA strands are separated

· RNA nucleotides are added by RNA polymerase

· Formation of RNA sugar phosphate backbone takes place

· New strand of RNA is synthesized after breaking the H bonds of RNA and DNA helix.

4) Post transcriptional process of mRNA:

mRNA transcripts into matured mRNA being capable to translated to proteins

This involves 3 steps

· Addition of 5’ cap

· RNA splicing

· 3’polyadenylated tail

5) Epigenetic mechanisms for the control of gene expression:

The mechanism includes:

· DNA methylation and hydroxymethylation

· Histone protein post transitional modifications

· Nucleosome remodelling

· Higher order chromatin reorganization

· Non coding RNA regulation

· RNA editing

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