4 - Gene organisation and transcription II Flashcards
What are the names for the initial RNA produced from a gene?
primary transcript
Pre-mRNA
heterogenous nuclear RNA (hnRNA)
Where does RNA processing occur and where does the DNA travel to after this?
occurs in the nucleus, and the fully processed RNA is exported to the cell cytoplasm to be translated
Describe the anatomy of a gene
- the gene promoter lies at the 5’ end
- exons contain the sequences that form part of the final mRNA
- introns are transcribed but edited out of the final mRNA
- sequence information is coded discontinuously in DNA
What is the splice donor site?
the junction between an exon and an intron
What is the splice acceptor site?
the junction between an intron and an exon
What do exons usually end with?
AG
What do introns start and end with?
start with GU
end with AG
RNA processing uses which type of proteins?
small Ribonuclear Proteins (snRNPs)
What end of the mRNA is the cap added to?
5’ end
How is the cap formed?
- the hydrolysis of terminal phosphates of mRNA to a diphosphate
- this reacts with α phosphate of GTP
- methylation at the N7 position in the purine ring to form 7-methylguanylate cap
What is the role of the cap?
to protect the mRNA at the 5’ end and enhance the translation of the mRNA
What virus interferes with the recognition of the cap?
Polio Myelitis
How and where is the Poly A tail formed?
it is added one base at a time
added 11-30 bases downstream of the sequence AAUAAA
What is thalassemia?
What is β-thalassemia?
an inherited disorder where there is an imbalance in the relative amounts of α and β chains making up haemoglobin
β-thalassemia is when there is a relative deficiency of β-chains
What causes β-thalassemia?
several types of β-thalassemia feature SPLICE SITE MUTATIONS IN β-GLOBIN GENE
