Gene Structure and Expression Flashcards
What is a gene?
A region of DNA that controls a discrete hereditary characteristic, usually corresponding to a single protein or RNA.
What does RNA Polymerase require?
Requires a DNA template • Requires activated precursors (nucleoside triphosphates - ATP, GTP, UTP and CTP)
What is a primer?
made up of the sequence elements found immediately 5’ to the gene that interact with RNA polymerase & other components of the transcription machinery
What is an enhancer?
increase transcription from a nearby gene but can operate over considerable distances , transcription factor binds
What are transcription factors?
proteins which bind to specific DNA sequences within the promoter or enhancers so as to increase or decrease gene expression
What is alternative splicing?
gene can be spliced in many different ways to produce different mRNA strands so different proteins
What is a polyA tail?
string of adenylate residues added to the 3’ end of an mRNA • Not found on rRNAs or tRNAs • Transcription proceeds past polyA site, transcript is cleaved, the polyadenylated (i.e. termination of transcription is distinct from polyadenylation) • Many genes have more than 1 poly A site
What is 5’ untranslated (5’UTR)?
5’ untranslated (5’UTR) is the region of an mRNA that is found upstream of the translated region • function of 5’UTRs is mostly unclear, may affect translational control can be included in mRNA
What is 3’ untranslated?
region of an mRNA that is found downstream of the translated region • 3’UTRs can determine the stability of the mRNA
What is redundancy?
Many amino acids are coded for by more than one codon
Why do some tRNAs require accurate base-pairing only at 1st two nucleotides?
This ‘wobble’accounts for finding that many alternative codons for a particular amino acid differ only in their 3rd nucleotide
How is the correct amino acid attached to the tRNA?
aminoacyl tRNA synthetases, ATP to AMP and 2 phosphates
What is the structure of a ribosome?
three tRNA docking sites and an mRNA binding site
A: Aminoacyl tRNAsite P: Peptidyl tRNA site E: Exit site
First step of translation
charged tRNA binds to vacant A-site • basepairing with mRNA codon determines which tRNA binds • binds immediately adjacent to preceding tRNA (no gap
Second step of translation
New peptide bond formed between a.a.s on tRNAs in P & A sites
