Genetics Flashcards
Which procedure is needed to get tissue from the placenta?
Chorionic villus biopsy
Which procedure is needed to get tissue from foetal skin/urine cells?
Amniocentesis
From what time of gestation can CVS be performed?
11.5 weeks
From what time of gestation can amniocentesis be performed?
15 weeks
Which technique can sequence a whole genome?
Array CGH
Which technique targets a specific part of the genome?
Fluorescence in-situ hybridisation (FISH)
What is the main difference between a mutation and polymorphism?
A mutation is a genetic change that causes disease, a polymorphism (per-se) does not
Give some characteristics of mutations
De-novo
Affects known gene
Reported in same phenoytpe
Give some characteristics of polymorphisms
Normal parent has it
Affects “empty” genetic region
When is FISH used?
When the missing bit of chromosome is too small to be picked up
When is prenatal genetic screening done in Scotland?
12, 16 and 20 weeks
What prenatal genetic screening is done at 16 weeks?
Maternal blood test to look for Down’s syndrome biochemical markers (NIPT)
How does non-invasive prenatal testing for trisomy 21 work?
Random next-generation sequencing reads to detect if there are more reads from chromosome 21 than should be
What clinical investigation is best to check for Down’s syndrome at 18 weeks gestation?
Amniocentesis
What genetic investigation is best to check for Down’s syndrome at 18 weeks gestation?
Array CGH
In a balanced chromosome rearrangement all the chromosomal material is present. True/false?
True
What occurs in an unbalanced chromosome rearrangement?
There is extra or missing chromosomal material
What occurs in Robertsonian translocation?
Two acrocentric chromosomes are stuck end to end
What does a Robertsonian translocation increase risk of?
Trisomy
In a parent with a balanced translocation, what would the aCGH look like?
Normal - only detects imbalance
What occurs in a balanced reciprocal translocation?
There is an exchange of material between nonhomologous chromosomes
What test is done to detect chromosome deletions/duplications?
Array CGH
What is pre-implantation genetic diagnosis (PGD)?
When a genetic test is performed on an embryo before re-implanting one
Give some advantages to PGD
Pregnancy less likely to be affected
Less likely to require TOP
Give some disadvantages of PGD
Requires ICSI (expensive/invasive)
Emotional rollercoaster for parents
Multiple pregnancy risk
When may parents consider PGD?
Parental chromosomal abnormality
X-linked disorder (re-implant female embryo)
Single gene disorder (CF/Huntington’s etc.)
