Question

A) Be able to interpret a promoter analysis experiment?

B) Know what alternative splicing is and how it could affect a gene product?

C) How silencers and enhancers work?

D) Describe how steroid hormone receptors work with hydrophobic ligands

Answer 1

A. Deletion mapping: It is a molecular biology method in which fragments of the upstream region of a gene are cloned upstream to a reporter gene such as GFP or GUS and transformed into a suitable host. If the given sequence is required for gene expression, we would observe the signal from the reporter sequence.

B. Alternative splicing uses alternative splice site acceptors/donors to produce different mature mRNA products. It increases the proteome of the cell without affecting the transcriptome.

See image.

C. Silencers are cis-elements that can work in a non-directional manner. They are bound by repressor proteins and inhibit the recruitment of RNA polymerase to target gene locus.

Enhancers are cis-elements that can work in a non-directional manner. They are bound by activator proteins and promote the recruitment of RNA polymerase to target gene locus.

D. Steroid hormones are hydrophobic in nature. So, they can easily cross through the lipid bilayer and bind to the cytosolic or nuclear receptor. They do not contain a cell membrane receptor. Most of the steroid hormone receptors are transcription factors. Upon ligand binding, the transcription factors get activated and mediate the downstream events (up/downregulation of target genes).