basic genetics- dna to protein Flashcards
What is a cells genome?
Every cell in our body has the same genome copy
However it might use only part of the genome or use it at different times (stages of life, response to external conditions etc.)
What does the human genome consist of?
First sequencing of human genome showed that only 21000 genes (3%) are encoding proteins
Other DNA-
~landing spots for proteins that influence gene activity
~strands of RNA w myriad roles
~where chemical mods silence stretches of chromosome
11224 DNA stretches are non-functional pseudogenes
What is a pseudogene?
Section of chromosome that’s an imperfect copy of a functional gene
Evolved to not need anymore
Contain biological and evolutional histories within sequences
Related to real genes (active in some cell types and individuals)
How are genes regulated?
Influenced by multiple stretches of regulatory DNA and non-coding RNA (small and long)
How is the gene formatted on DNA?
The coding strand carries genetic info (other is template)
mRNA is identical to the coding strand (but T-U) and complimentary to the template
How is gene expression started?
RNA polymerase binds to the promoter sequence (short sequence eg. TATA box)
3 types of RNA polymerase but mainly interested in polymerase II (mRNA precursor)
What is RNA polymerase II?
Composed of several subunits and accessory proteins in a defined order
TFIID recognises the TATA box (basal promoter) and ensures correct site is used
What is an enhancer?
Sequence that controls efficiency and rate of transcription in specific cell type and controls timing of expression
What is the strength of a promoter or enhancer?
Can be strong or weak affecting rate therefore expression
Changes in strength can result in disease
Where are enhancers and promoters on the strand?
Can be far from each other
Promoter- usually on 5’
Enhancer- 5’ or 3’ in introns or even non-coding strand
Brought close by looping of DNA due to interactions (cohesion complex)
Activators facilitate looping and repressors inhibit
What are transcription factors?
Bind to promoters and enhancers and recruit RNA polymerase
Eg. TFIID
Trans acting- on the gene
Cis acting- come from elsewhere
Is RNA single stranded?
Yes but interactions w complementary sequences on same molecule can allow it to fold into 3D
So some structural and catalytic functions
What is RNA capping?
Cap on 5’ end
Stabilises mRNA so can be transported out of nucleus
Assembly point for proteins needed to recruit small subunit of ribosome to begin translation
What is alternative splicing?
Introns are cut out of sequence by spliceosome
Several variants of same protein produced by one gene (diff exon sequences)
Leads to diversity
Mutations at splice site can result in malfunctions
What are the different types of RNA?
mRNA- produces proteins
rRNA- build ribosomes to produce proteins
tRNA- bring AAs and line them up
Non coding RNA- regulatory roles
Small nuclear RNA- part of spliceosome
Small nucleolar RNA- make ribosomes and part of splicing
Micro RNA- regulatory roles
