LECTURE 21 - NILSON 7 Flashcards
what are piRNAs
short single stranded RNAs (26-30nt in mammals) that interact with a protein complex (piwi-argonaute) that destroys complementary target mRNAs
difference between siRNAs and piRNAs
how do piRNAs repress transposon mobility in the germ lines of Drosophila
transposable elements insert randomly into the chromosome, but they can sometimes land in a pi cluster, where they become destructive
if they insert somewhere else that is not a pi cluster, they are transcribed, translated into the transposase and are able to move
what is the explanation for the fact that lab strain female and wild caught male produce sterile progeny while lab strain male and wild caught female make fertile progeny
lab strain female has no P elements in her pi cluster and thus no piRNA in her eggs
this means she has no genome surveillance, P elements introduced in the male genome can mobilize and cause instability in the F1 germline, making sterile progeny
On the other hand, wild caught female has P elements in her pi cluster and thus has piRNAs that can block the transposons in the germline of the embryo
the F1 progeny are fertile
why do we only consider the female/why do her gametes matter more?
the egg has a lot more content than the sperm
the sperm is not as big of a contribution
what is the function of p53
mutations can induce tumor formation
p53 may also play a role in repressing the mobility of certain transposable elements which may cause tumors, so its mutation can be deleterious
Wilms tumors mutant for p53 and LINE expression
the tumors which have a mutation for p53 have more expression of LINE
hypothesis: loss of p53 in kidney cells leads to deregulation of retrotransposon activity and to tumorigenesis
what experiment was done with p53 mutants in drosophila and TAHRE retrotransposon mobility
what happens to that same experiment when you add human p53 rescue, and also p53 variants commonly seen in cancer patients
these mutations remove the ability to repress the movement of transposable elements, leading to cancer
what is a mutation
also a change in the sequence
where do most mutations occur and where do they need to be to be inherited
what can mutations do
what are chromosomal mutations
gain or loss of all or part of a chromosome
what are insertional mutations
insertion of large regions of DNA (transposable elements)
what are point mutations
change/addition/deletion of a single or more nucleotides
why are germline mutations passed on to approximately half of the next generation only
mutations happen only on one allele
