genetics Flashcards
what is the inheritance of Lynch syndrome?
autosomal dominant
what are the 4 (or 5) genes implicated in Lynch syndrome
What type of genes are they?
MLH1 (yes, ‘L’)
MSH2
MSH3
PMS2
(EPCAM)
they are DNA mismatch repair genes
which cause ‘microsatellite instability’
What do you use to to identify endometrial cancer tumours with mismatch repair (MMR) deficiency?
Immunohistochemistry (IHC)
If immunohistochemistry of an endometrial tumour is abnormal with loss of MSH2, MSH6 or isolated PMS2 protein expression, offer germline genetic testing to confirm what?
Lynch syndrome
In endometrial tumour testing, if MLH1 is lost on immunohistochemistry (IHC), you test for MLH1 promoter hypermethylation. What do you do with that result?
MLH1 promoter hypermethylation is NOT detected, then DO offer germline genetic testing to confirm Lynch syndrome.
If there IS promotor hypermethylation you DON’T test for Lynch syndrome
Kallman syndrome is characterised by…
ANOSMIA
colour blindness/optic defects
and hypogonadotropic hypogonadism due to defective migration of GnRH neurones from the olfactory placode to the hypothalamus (congenital GnRH deficiency)
Homocystinuria can be autosomal recessive, or due to deficiency of which vitamins?
B6, B12 or folate
Which condition is homocystinuria like? What happens to the lens of the eye?
Marfans
Downward dislocation in homocystinuria
what is transcription
copying a gene’s DNA sequence to make an RNA molecule
what is the main transcription enzyme
RNA polymerase
what is the RNA molecule made by transcription called
messenger RNA (mRNA)
what are the typical lab results in Kleinfelters (XXY) and what is the pathogenesis behind this
Destruction and hyalinization of the seminiferous tubules cause a reduction in the function of Sertoli cells and Leydig cells, leading to decreased production of testosterone.
LH and FSH are subsequently high to try to increase testosterone
SHBG is also high
karyotype of male Edwards syndrome
47XY
what is a transcription factor
a protein at controls the rate of transcription of genetic information from DNA to mRNA, by binding to a specific DNA sequence. They ‘turn on and off’ genes in order to make sure they are expressed in the desired cells at the right time.
what is CRISPR
an acronym for clustered regularly interspaced short palindromic repeats that arise in prokaryotes from fragments of bacteriophage (viral) infections to that bacterium prokaryote, and provide a form of heritable, acquired immunity
what is Cas9
a nuclease which can be complexed with a synthetic guide RNA to cut DNA at a desired location, allowing existing genes to be removed or new ones added in vivo.
Hence CRISPR/CAS9 is the gene editing technology
is COVID and Zika virus ssRNA, dsRNA, ssDNA or dsDNA?
ssRNA
90% of cases with CAH cause by mutation of CYP 21, which chromosome is this gene located
chromosome 6
CYP21 and CYP21P are located within the major histocompatibility complex on chromosome 6p21.3
