Small RNAs in the regulation of biological processes

Question 1

What is the C-value paradox?

Answer 1

The size of the genome is not necessarily related to its complexity.

Question 2

What are non-coding RNAs? Give some examples.

Answer 2

Any RNA that isn’t translated into a protein (i.e. anything except mRNA) EXAMPLES: tRNA, rRNA, siRNA

Question 3

Describe how RNA can be used to block mRNA function.

Answer 3

Antisense RNA can be synthesised which binds to the complementary sense RNA forming double stranded RNA thus preventing it from being translated

Question 4

Describe the formation of siRNA.

Answer 4

You begin with viral dsRNA DICER cuts the dsRNA into smaller pieces (21-25bp)
AGO proteins then remove the passenger strand only leaving the strand that is anti-sense to the target RNA
The RISC complex associates with the single stranded RNA and cleaves the target mRNA when bound with the siRNA

Question 5

What feature of siRNA allows it to be used as a viable therapy?

Answer 5

It is small enough to enter the cell without causing a detrimental cytokine response.

Question 6

What did the Lin-14/Lin-4 experiment show?

Answer 6

There is genomically encoded miRNA that is involved in gene regulation.

Question 7

Describe the production of miRNA.

Answer 7

miRNA is made as much bigger RNA known as pri-miRNA
pri-miRNA is processed to form pre-miRNA
Further processing allows the miRNA to be passed into the RISC complex

Question 8

What is the classic arrangement of miRNA within the genome?

Answer 8

It occurs as a match-bulge-match arrangement in the genome. One of the matching regions is usually a 3’ UTR and the other is a seed region

Question 9

Give an example of an alternation in miRNA expression causing disease.

Answer 9

Chronic Lymphoid Leukaemia – deletion of part of gene on chromosome 14 leads to loss of miRNA and promotes CLL