5- Small Rna In Regulation Flashcards
What do these stand for: miRNA siRNA piRNA shRNA RNAi RISC
Micro rna Small interfering rna Piwi interacting rna Small hairpin rna Rna interference Rna induced silencing complex
What does the c value show
Genome size (not organism complexity)
Give examples of non coding RNA and their functions
Housekeeping (rRNA, tRNA, ncRNA)
miRNA (control translation of most genes)
siRNA, (viral defence, by short term gene silencing)
piRNA, (germ cell production)
long ncRNA (e.g. Xisco for X chromosome inactivation and many more antisense RNAs for imprinting and gene regulation)
What can be used to black mRNA function
Antisense RNA: strand hybridise to form dsRNA so not translated
Describe how DICER silences mRNA
DICER chops dsRNA into sections of 21-25bp
The passenger strand is removed by AGO (argonauate piwi proteins), leaving antisense strand to target mRNA
RISC proteins are formed which cleave the mRNA at target sites with complementary sequences to the guide siRNA
Give and example where DICER is essential
Early embryonic stages, because stem cells would be unable to differentiate without mRNA inactivation
Why can siRNA with +25bp be problematic
Can cause cytokine responses
Give an example of an miRNA regulating another gene
Lin-4 is a miRNA which binds to lin-14, in early development, so protein no longer produced
Describe miRNA production
Starts as pri-mRNA, then chopped up and exported to cytoplasm as pre-mRNA
Further processing allows it to be passed to RISC complex, used as siRNA
Describe chronic lymphoid leukaemia
Deflection of part of chromosome 14 leads to loss of miRNAs
What is the most important region of the miRNA for targeting In bioinformatics
The seed region, lies 2-8 from 5’ end
Why is it relatively easy to identify miRNA
Usually have 2 matching areas separated by a bulge
