G8 Flashcards
describe an autosomal dominant inheritance and and give an example
half of offspring affected
unaffected individual doesnt transmit disease
eg. Anchroplasia - dwarfism
describe an autosomal recessive inheritance and give an example
ussually only one generation affected
if both parents carriers = 1/4 affect, 1/2 carries, 1/4 not affects
eg. CF
What is X linked recessive inheritance and give an example
carrier females transmit disease to half their sons and carrier status to half their daughters
eg. X linked haemophilia
c.76A>T
substitution A->T in coding DNA
c.76_78delACT
range of affected resieus 76-78 by deletion of ACT
c.76dupA
duplication at 76 of A base
c.76delA
deletion at 76 of A
c.76-83inv
inversion between 76 and 83
c.76_77insG
insertion but it duplication describe as duplication
G inserted between 76 adn 77
p:Lys76Asn
p refers to primary translation product
at AA 76 varient results in sub of asparagine instead of normal lysine
p.Tyr356X
X indicates a nonsense codon has been generated
c.1408+2T>G
second nucleotide after c.1408 that would normally be the invariant T of splice site is insead a G
c.789-1G>A
first nucletodie before c.780 that would normally be invariant G of splice site is now an A
c.69_71del(p.Val15del)
in frsame deletion deletes aa valine
c.546insA(p.Val170fs)
out of frame insertion inserted valine causing frameshift after 170
what letters denote each type of reference seqeunce
c= coding DNA g- genomic DNA r = coding RNA reference seq n = non coding RNA ref seq m = mitochondrial DNA seq
What is HGVS
human genome variation society
what terms do HGVS use to prevent confusion from using terms like SNP or mutation
sequence variatn
alteration
allelic variant
what classes and terms do HGVS use to recognise that some variants can be harmful
5 = affects function 4 = probs affects function 3 = unknown 2- probs doesnt affect function 1= doesnt affect function
what casues anchrondoplasia
Fibroblast growth factor receptor 3 p FGFR3 - represses ossification of chondrocytes that proliferate and mature into bones at growth plate
- in anchondroplasia ossification is further pressed
what is ossification
process where catilage is turned into bone
why is it difficult to predict what the ouctome of splice site mutations will be?
as genes use alternate transcriptional start sites, alternate combos of exons, althhough usually one isoform RNA is shown, cell can produce several different ones at the same time and this remains poorly understood
what is nonsense mediated decay?
highly conserved quality control survelliance mechanism
recongises and degrades defective mRNAs with premature termination codons PTCs which if translated could produce harmful aberrant proteins
(can occur indep of any DNA mutations as a result of errors during transcription, processing or packaging)
what happens to EJCs in normal splicing and i PTC containing mRNA
normal: proteins of exon junction complec = deposited 2-24 nts upstream of each exon/exon unction, and are displaced by scanning ribosome during inital round of translation.
PTC: upon recognition of stop codon, a termination complex is fomred, in PTC containing mRNA, EJCS downstream of PCR are not displaced allowing the termination complex to interact with the EJC triggering NMD.