Testing for genetic abnormalities Flashcards
Copy number variants
Large number of duplications/deletions
Chromosomal aneuploidy
Loss of chromosome
What is a de novo mutation
Occurs spontaneously
Syndromic presentation
Collection of findings, suggesting underlying known cause
Non-syndromic presentation
No recognised underlying syndrome
What is light microscopy good for?
When chromosomes are replicating and condense, they become visible - detects aneuploidy, trisomy 21, turners etc
G banded karyotype
Dye chromosome with particular stain so resolution is higher - shows bands on loci
Microarray
factory produced DNA binds to specific sections of the gene - this causes it to fluoresce - no light indicates deletions. This is useful if you know what you are looking for
Antenatal screening
- Combined test: 10-14 weeks, blood test for PAPP-A and B HCG + nuchal translucency
- Quadruple test offered when: NT measurement not obtained/CRL >84mm/too late in pregnancy
- Quadruple test: 14-20 weeks, AFP, B HCG and inhibin levels
- 20 week screening: USS 18-21 weeks for:
NIPT
non-invasive prenatal testing, detects foetal DNA in mother’s bloodstream - offered if combined or quadruple are high risk
Pros karyotype analysis
Cheap
Visualise aneuploidy
large structural changes
Cons to karyotyping
Limite information
Miss subtle abnormalities
Pros micro-array
Answer specific questions
Cheap
Cons micro-array
Miss small/rare mutations
Only specific pathologies tested
Pros exam sequencing
Analyse thousands of genes
Cheaper than whole genome
