Genetics Flashcards
Sense mutation
The amino acid is not altered
Missense mutation
Alters the amino acid sequence
Mutation in Sickel cell anaemia
Substitution
GAG to GTG (Glu- Val)
Mutation in HD and Fragile X
Insertion
Trinucleotide repeats
22q11.2 deletion Syndrome
Clef Palate, heart defects, autoimmune disorders
Trisomy 13
Patau
Trisomy 18
Edwards
Monosomy X in women
Turners
Disomy X in men
Klinefelters
Hereditary haemochromatosis inheritance?
Autosomal recessive
2 examples of Imprinting Disorders
Pader Willi and Angelman Syndrome
What is an imprinting disorder?
- If one parent’s gene is expressed and the other is ‘silenced’
What is a karyotype?
Gives you a picture of someone’s chromosomes
When is FISH used?
When a patient has features which are confident with a well-described micro deletion or micro duplication syndrome
When is quantitative fluorescence PCR used?
- To count/quantify specific chromosomes
- Usually used for trisomies
When is Array CGH used?
-Detects chromosome deletions and duplications but not structural chromosomal changes
Calculating risk in recession conditions when individual has a sibling affected by the recessive condition
2/3 (sibling affected) x 1/24 (general population risk) x 1/4 (autosomal recessive)
Example of a condition with genetic anticipation
HD
When to do CVS
11.5wks
When to do amniocentesis
15wks
47XY + 13
Bilateral clef palate
Post-axial polydactyly
Holoprosencephaly (facial defects)
Patau Syndrome
45,X
Neck webbing and oedema
Turner Syndrome
What would aCGH look like in the parent with a balanced translocation?
Normal
aCGH only detects imbalance
A diagnosis may be suspected, which test?
Chromosome analysis or array CGH
You need to know the diagnosis (strong clinical feat, which test?
FISH
Which weeks to detect the following on US:
- Cardiac
- Microcephaly
- Short limbs
- Cardiac 12-20wks
- Microcephaly usually after 22weeks
- Short limbs usually after 22wks
