8: Genetics 2 Flashcards
By which method can you check the whole genome for balanced mutations only?
Array CGH
What are some examples of balanced chromosomal mutations?
Deletions
Duplications
Apart from genetic testing, how else can you detect genetic diseases in a foetus?
Ultrasound
performed at 12 and 20 weeks
What is trisomy 13 called?
Patau syndrome
Incompatible with life in most causes - lots of birth defects, failure of one or both eyes to develop (cylopsia)
What are two common causes of intra-uterine growth restriction (IUGR)?
Chromosomal abnormality
Placental insufficiency
Which causes of IUGR result in
a) symmetrical growth restriction
b) asymmetrical growth restriction?
a) Symmetrical IUGR suggests GENETIC DISORDER
b) Asymmetrical IUGR suggests PLACENTAL INSUFFICIENCY
What is the appearance of asymmetrical IUGR secondary to placental insufficiency?
Why?
Enlarged head; smaller trunk and limbs
Brain growth prioritised
What is the mode of inheritance of Duchenne muscular dystrophy?
X-linked recessive
A woman carrying the recessive dystrophin mutation and an asymptomatic male have a child.
What is the percentage chance of them having an
a) affected child
b) affected boy?
a) 25% (recessive)
b) 50% (X-linked recessive, so can only be inherited by boys)
What is the percentage risk that a child will inherit a
a) autosomal dominant
b) autosominal recessive disorder?
a) 50%
b) 25%
The chances of a child inheriting an autosomal recessive disease is 25%.
In which group is this risk increased?
Consanguineous offspring
inbreeding
Which percentage of foetuses have a congential disease?
0.05%
Relatively uncommon
Which percentage of embryos have a genetic error before implantation?
50%
Which method of genetic testing is the best for identifying a known gene mutation in a foetus?
NIPT
i.e taking a maternal blood sample and looking for foetal DNA
also useful for sex determination
In cases of X-linked recessive disorders like DMD, why is non-invasive prenatal testing useful?
If NIPT identifies no Y chromosomes i.e it’s a girl, you can stop worrying because DMD is inherited by males only
Which form of genetic testing involves work on embryos isolated from a woman?
Pre-implantation genetic diagnosis
Pre-implantation genetic diagnosis (PGD) is often combined with which assisted conception therapies?
IVF
ICSI
Which genetic analysis technique allows you to visualise the sex chromosomes of an embryo and thereby determine if it’s a boy or girl?
FISH
One of its few remaining uses - fluorescent probes
What are the different names for the cell mass in the first days of embryogenesis?
Zygote
2 cell mass
4 cell mass
8 cell mass
Morula
Blastocyst
From which stage of the embryo are cells taken for PIGD?
8 cell stage
What is the success rate (“take-home rate”) of IVF?
30%
Which can be difficult for the parents to accept
What is a major risk of IVF, which is avoided by not overstimulating the ovaries?
Multiple pregnancy
Which genetic disorders are caused by
a) trisomy 13
b) trisomy 18
c) trisomy 21?
a) Patau syndrome
b) Edwards’ syndrome
c) Down’s syndrome
revise week 5 endocrine and ivf process
genetics terminology - come back to this, lots more to learn
