gene expression and human disease 2

Question 1

How is translation initiated?

Answer 1

• small ribosomal subunit scans along RNA from 5’ end
• it carries initiator tRNA and initiation factors
• joined by the large subunit

Question 2

Explain how a frameshift mutation can lead to congenital deafness?

Answer 2

• c35delG mutation in the connexin 26(GJB2) gene, leads to a stop codon
• frequent cause of autosomal recessive congenital deafness

Question 3

What is a mis-sense mutation?

Answer 3

where one of the letters is replaced by another resulting in a different amino acid being coded for

Question 4

What is a non sense mutation?

Answer 4

where the mutation causes a stop codon to be put there

Question 5

How can a mis-sense mutation cause sickle cell anaemia?

Answer 5

• mutation in beta-globin protein
• codon for glutamic acid changed to codon for valine

Question 6

How can a non-sense mutation cause beta-thalassemia?

Answer 6

mutation near start of exon 2 makes stop codon instead

Question 7

What is microRNA (miRNAs)

Answer 7

• 21-22 nucleotides long
• non coding RNA
• bind target sequences in 3’ UTR
• cause translational repression/degradation of mRNA transcripts

Question 8

How can loss of microRNA expression cause chronic lymphocytic leukaemia?

Answer 8

• 13q-14.3 deletion
• downregulation of miR-15a and miR-16-1
• induces overexpression of BCL2
• reduced apoptosis

Question 9

How can miRNA be involved in regulating metastasis?

Answer 9

• miR-200 family can promote growth of primary tumour and colonisation of metastases
• miR-31 can inhibit movement and invasion of cancer cells to new location

Question 10

Why are miRNAs good biomarkers?

Answer 10

• found in circulating blood and other bodily fluids
• stable as they are bound to proteins or protected inside exosomes/microvesicles
• can be detected using qRT-PCR on standard machines