NAGE 5 Flashcards
What is meant by the “C-value” ?
Genome size
The complexity of an organism is not related to its genome size. T or F?
T
What is a lot of the functional non-coding DNA involved in?
Regulating the expression of coding genes.
What is a non-coding RNA?
Any RNA molecule that is not translated into a protein.
does not include mRNA
Give examples of non coding RNAs.
- Housekeeping ncRNAs (rRNA, tRNA, snRNA)
- siRNA/RNAi
- microRNA - controls translation of most genes
- piRNA - important for germ cell production
- Long ncRNA
What is long ncRNA used for?
Important for x chromosome inactivation
How can antisense RNA be used to block mRNA function?
- Reverse of gene (that you want to block) transcribed. The newly transcribed reverse = antisense RNA
- Antisense and sense RNA strands H-bond and form double strand (this is dsRNA). (aka mRNA and antisense RNA form H bonds)
- This means sense RNA can’t be translated.
Where does siRNA come from?
dsRNA
Explain how genome silencing works?
- Dicer breaks up dsRNA fragments into 21-25bp fragments (endonuclease activity).
- One “passenger” strand is removed. This requires Argonaute-Piwi proteins (AGO). (Remaining strand is antisense to target strand).
- The now single stranded RNA associates with RISC complexes.
- RISC recognise mRNA strands with complementary sequences to the siRNA strand that they are joined to, and cleave the mRNA strands. Gene is silenced.
What can be used to prevent cell division?
siRNA
What is shRNA?
Small Hairpin RNA. One long piece of RNA that loops back on itself.
There are miRNAs present in the genome that are involved in regulating other genes. T or f?
T
Explain how gene knockdown happens.
Pro-pre-miRNA is cleaved and exported to cytoplasm as pre-miRNA.
Pre-miRNA processing enables it to pass down into RISC complex.
Pre-miRNA becomes miRNA - it then targets genes at RNA level and silences them.
Gene knockdown - decreasing amount of protein you get from a gene.
THERE ARE pre-miRNA SEQUENCES THAT END UP AS siRNA IN THE RISC COMPLEX!
