Lecture 17 Flashcards
What is a gene?
- The basic physical and functional unit of heredity
- Are instructions to make proteins
- Made of DNA
Gene expression definition?
The process by which inheritable info in a gene (DNA sequence), is made into a functional gene product (protein)
Conformation of RNA?
Single stranded
Sugar in RNA?
Ribose
Bases in RNA?
Adenine, uracil, guanine and cytosine
What are 3 subtypes of RNA?
mRNA, tRNA and rRNA
mRNA?
- Produced by transcription of protein-coding genes
- Translated (coding)
- Contains instructions for protein synthesis
tRNA?
- Not translated (non-coding)
- Produced by transcription of tRNA genes
- Covalent binding of amino-acids and their transport to the ribosome
rRNA?
- Not translated (non-coding)
- Produced by transcription of rRNA genes
- Structural and enzymatic role (ribosome)
Which direction does RNA grow in?
- 5prime to 3prime
- The direction of the coding strand (sense strand)
Does all DNA code for proteins?
No only genes do
Transcription factors (TFs)?
Specialised proteins that help determine which DNA sequences should be transcribed and at what time
RNA synthesis initiation?
RNA polymerase unwinds DNA double helix and initiates RNA synthesis
RNA synthesis elongation?
Additional nucleotides are added to the 3’ end of RNA molecule. DNA double helix re-forms following transcription
RNA synthesis termination?
At the end of each gene there is a termination site which tells the RNA polymerase to stop.The copied single stranded sequence is called Precursor heterogenous nuclear RNA (hnRNA) or pre-messenger RNA. RNA transcript and RNA polymerase are released
Which direction does RNA polymerase move along the template DNA strand?
- 3prime to 5prime
- Antisense
Eukaryotic RNA processing?
- 5’ Capping
- 3’ maturation:
cleavage &
polyadenylation- - Splicing
- Editing
- Transport of RNA to
Cytoplasm - Stabilisation/ Destabilisation of mRNA
What is 5prime capping?
Adding 7MeGuanosine (modified guanine) to the first RNA nucleotide in the 5prime to 5prime direction
What are the functions of a cap?
- Essential for the ribosome to bind to the 5’ end of the mRNA
- Protection from some ribonucleases
- Enhanced translation
- Enhanced transport from nucleus
- Enhances splicing of first intron for some mRNAs
What does polyadenylation do?
- The poly-A tail makes the RNA molecule more stable and prevents its degradation
- Additionally, the poly-A tail allows the mature messenger RNA molecule to be exported from the nucleus and translated into a protein by ribosomes in the cytoplasm
