BIOC Module 2 (Molecular biology)

Gene

A region of DNA that provides instructions to make an RNA molecule.

Components of a gene

Promotor and transcribed region

Structural difference in the transcribed region between Eukaryotic and Prokaryotic genes

• Eukaryotic genes: Contain both exons (translated coding regions) and introns (untranslated non-coding regions that must be spliced out).

• Prokaryotic genes: Contain no introns and cannot perform mRNA splicing.

How RNA polymerase creates mRNA during transcription

RNA polymerase binds to the promoter and uses one DNA strand as a template to build a complementary single-stranded mRNA molecule. The sequence matches the non-template DNA strand, except Uracil (U) replaces Thymine (T) in RNA

Transcription factor and two main types

A transcription factor is a protein that binds to specific DNA sequences in the promoter region to control whether RNA polymerase binds and transcribes a gene. The two main types are activators and repressors.

How do Eukaryotic and Prokaryotic cells differ in where and when transcription and translation take place?

Eukaryotic transcription happens in the nucleus where mRNA is spliced and then is moved to the cytoplasm for translation into proteins. In Prokaryotic cells both of these happen in the cytoplasm as there is no nucleus.

Promotor

This region controls transcription and contains RNA polymerase binding site and transcription factors binding sites.

Activator

Encourage RNA polymerase binding and creation of mRNA.

Repressor

Prevent RNA polymerase from binding and mRNA from being made.

Alternative splicing

It is when different portions of mRNA are removed during the RNA processing stage of transcription which allows us to make more proteins than genes.

Ubiquitously expressed genes

Genes needed for basic cellular function, expressed in almost all cells.

The purpose of translation

To make a polypeptide chain using the message encoded by mRNA

Cytoplasm

Where translation occurs

Ribosome

A complex structure made of protein and rRNA (ribosomal RNA)

Codon

A set of three DNA or RNA bases to code for an amino acid, stop or start of a protein

Universal genetic code

The codon system which is common across all life.

tRNA

Transfer RNA, used to ensure the same mRNA sequence is always translated the same way. (makes the same protein).