Gene Regulation

Selective gene expression

Only certain genes are expressed (used to make proteins). Explains why identical twins can look different

Operon

Structural genes and DNA sequences that regulate expression

Promoter

DNA sequences upstream of transcription start site where RNA polymerase and transcription factors bind to initiate transcription

Operator

Site of repressor binding

Structural genes

Code for the proteins/enzymes of the operon

Regulatory gene

Code for repressor protein

Repressor proteins

Can bind to operator and prevent transcription and expression of the structural gene

Inducible operons

The genes are normally off. Repressor proteins are normally bound to the operator. An inducer binds to the repressor proteins, so it will unbind. This causes the gene to be transcribed and expressed

Repressible operons

Gene is normally on. A corepressor can bind to the repressor protein, so that it will bind to the operator and block protein synthesis and gene expression

How do histones affect gene regulation?

How tightly DNA is wrapped in a histone affects gene expression. Tighter DNA is harder to transcribe and vice versa

Methylation

The addition of a methyl group. Causes the DNA to wind tightly

Acetylation

The addition of an acetyl group. Causes the DNA to loosen up

Epigenetics

The change of gene expression due to reversible modifications of DNA

Transcriptional Control

Transcription factors help RNA polymerase bind to promoters, activate only certain parts of a gene, and regulatory sequences either enhance transcription or prevent expression

Posttranscriptional control

The primary transcript must be processed, and introns are removed. Alternative splicing can allow one gene to express multiple proteins

Translational control

MicroRNAs can disable translation of mRNA

Posttranslational control

They way a protein is folded and affect its expression. Protein lifespans are controlled by proteases.

How is gene regulation expressed in embryonic development?

As the organism grows, stem cells begin to differentiate and some genes are deactivated. The cells later separate into groups and develop into the complex systems of the human body

Hox genes

Determine the structure of certain body parts, but do not assemble the parts or build the parts. Their protein products are transcription factors