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
