Lecture 7 Flashcards
Describe RNA
less stable and single stranded but can base pair, form 3D shapes and has a variety of functions, stems that pair and loops that don’t
How are multiple products produced from single pre-mRNAs?
alternative splicing
• Alternative 5’ splice-site selection or 3’
• Cassette-exon inclusion or skipping
• Intron retention
Whats iso forms?
a member of a set of highly similar proteins that perform the same or similar biological role
How many iso forms are in drosophila?
39,016
Where can introns occur
5’ and 3’ UTR and the protein coding region
How can RNA editing increase the number of iso forms?
- Common in parasits such as Trypanosoma
- Mature mRNA sequence donest correspond to gene sequenece
- In vivo modifications, Splitting of mRNA, addition or deletion of uridine from mRNA
- Multiple proteins can be produced from a single gene
Describe Apo-lipoprotein B
4563 codons in liver and 2152 codons in intestine – produces a stop codon
Describe the regulation of iron
- In iron starved cells 0 cytosoilic acontitase binds to mRNA allows transferrin receptor to be made causing iron uptake into the cell
- Excess iron – binds to cytosolic aconitase exposing mRNA allowing endonuclease to access RNA and loose poly A tail which stabilises the mrNA so no uptake
- Binds to other end for ferritin so no ferritin, excess iron – binds to enzyme so ferritin made
What did fire and Mello do?
injecting double stranded RNA reduced expression of genes but reducing levels of mRNA, RNA interference which is very specific
Describe RNAi gene silencing
inject double stranded RNA and is processed – one strand and is processesd into a protein containing argonaute or Piwi which bind with guide single stranded RNA and target RNA by finding complementary sequence on the mRNA – target cleavage, lead to translational repression and eventual destruction of target RNA, formation of heterochromatin on DNA from which target RNA is bring transcribed
What causes degradation?
miRNAs and siRNAS produced and block translation
Describe miRNA
cropped in nucleus and transferred to cytosol, enzymes involved in cleavage are known as dicers – enzymes target single strand – passenger strand is degraded and guide strand binds to RNA induced silencing complex including argonaute proteins which can cleave RNA, extensive match between guide strand and mRNA – Piwi cleave the RNA removing poly A tail leading to rapid mRNA degregation – no translation
What is highly specific degradation?
Less extensive match – still bonds which can interfere with transcription
What are miRNAs?
key regulators in development, cell birth and death and cancer – present in both plants and animals
