Insect Genomics Exam 3: Lecture 36 - Rnai

Front 1

What are the competing processes that determine genome size?

Back 1

Tolerance of junk DNA (transposons, pseudogenes). High tolerance = growth of genome. Gene duplications. Large deletions cause smaller genomes. Dros have low tolerance and large deletions.

Front 2

RNAi pathway

Back 2

ds RNA recognized by Dicer and cleaved into short pieces, pieces are recognized by RISC which cleaves them into individual base pieces

Front 3

RNA-importer protein

Back 3

In nematodes, vertebrates, insects except Dros. Facilitates uptake of ds RNA

Front 4

RNA-mediated RNA-polymerase

Back 4

In nematodes and vertebrates, missing in insects so RNAi less effective. Can spread RNAi effect through some animals

Front 5

RNAi in genome defense

Back 5

Knock down RNAi with RNAi = transposons go crazy and some viruses are lethal

Front 6

Piwi proteins and piRNAs

Back 6

RISC-like proteins, mediate suppression of transposon expression and activity in germline, piRNA sometimes controlled by P insert near X telomere

Front 7

microRNAs

Back 7

Short transcripts that fold into perfect or imperfect hairpin structures that are recognized by dicer. 2 pathways: perfect match = RNAi pathway, small mismatch = inhibit translation by binding to mRNA 3' UTR