Sesh 8: Gene Expression Flashcards
DNA to mRNA is _____________, and mRNA to protein is ____________.
- Transcription
2. Translation
Transcription occurs in the _______ and translation occurs in the _________.
- Nucleus
2. Cytoplasm
What is a gene?
A stretch of DNA at a specific chromosomal locus, coding for a specific protein.
What direction is a polypeptide elongated in?
N to C terminus.
What are the 3 stages of DNA replication, transcription and translation?
- Initiation
- Elongation
- Termination
What 3 general components are needed to make DNA, RNA and proteins?
- Enzymes
- Activated substrates
- A template
What is a TATA BOX?
A sequence within the promoter sequence of a gene that is recognised by transcription factors, to set the direction of transcription.
What do transcription factors do?
Bind the promoter sequence of a gene, to set the direction of transcription, and recruit RNA polymerase.
RNA polymerase binds 1 nucleotide __________ of where transcription begins.
Upstream.
Pre-mRNA is synthesised from the _________ strand, and made in the __ to __ direction.
- Template/ non-coding
- 5’
- 3’
RNA polymerase reads the template DNA strand in the __ to __ direction.
- 3’
- 5’
To make mRNA in 5’ to 3’ direction.
What 3 types of RNA processing occur?
- Capping
- Polyadenylation
- Splicing
What is RNA capping?
A 7-methylguanosine cap is added to the 5’ end of pre-mRNA via a 5’ to 5’ triphosphate link.
Protects against degradation and has a role in translation.
How does polyadenylation of pre-mRNA occur?
- Endonuclease recognises a specific polyA site, which then cleaves the RNA- ‘falls off’ the DNA
- PolyA polymerase then adds ~200 adenylate residues to the 3’ end
What subunits make up a eukaryotic ribosome?
40S+60S–> 80S ribosome
What is the most abundant type of RNA in the body?
Ribosomal RNA (rRNA)=~80%
What is the adaptor molecule for translation?
tRNA
What is meant by the degenerate nature of the genetic code?
Some amino acids are coded for by >1 triplet code….due to ‘wobble’ base.
What is the start/initiation codon, and what amino acid does it code for?
AUG codes for Methionine. At N-terminus of all proteins unless cleaved off after translation.
What are tRNA stem loops?
Loops formed by H bonds between anti-parallel complementary sequences, from a single-stranded structure.
Which part of the tRNA does an amino acid bind to?
The 3’OH end.
A charged tRNA is referred to as an…….?
Aminoacyl tRNA
A tRNA anticodon of 5’CAU would recognise the mRNA codon_____?
5’AUG- Met
Anticodon needs to be in 3’ to 5’ =UAC=complementary to AUG.
How is translation initiated?
A ‘special’ methionyl tRNA recognises 5’ cap of mRNA & moves along until reaches start codon (AUG). Ribosome 40S subunit is also associated.
Once the tRNA anticodon has recognised this, the 60S ribosome subunit associates to form a fully functional ribosome.
