Sesh 16 And 17: Cytogenetics Flashcards
Define cytogenetics.
The study of genetic constitution of cells via the visualisation and analysis of chromosomes.
List 4 uses of cytogenetics.
- Pre-natal screening
- Assess future reproductive risks
- Accurate diagnosis/prognosis
- Better clinical management
What are the 2 prenatal diagnosis methods?
- Chorionic villus sampling
2. Amniocentesis
What is polyploidy?
Gain of a whole haploid set of chromosomes, most commonly caused by polyspermy.
Lethal chromosome abnormality.
What are the possible causes of aneuploidy?
- Non-disjunction in meiosis or mitosis
- Anaphase lag
What are the clinical names for trisomy 21, 18 and 13?
21=Down syndrome
18=Edwards syndrome
13= Patau syndrome
What is X chromosome inactivation?
- Only 1 X chromosome ever active
- i.e. Turner syndrome
- phenotype differs depending on parental origin of X
What is a reciprocal translocation?
A 2 break re-arrangement causing exchange of genetic material between 2 non-homologous chromosomes.
No genetic material gained/lost.
Can produce balanced/unbalanced gametes.
What is the most common form of segregation in meiosis I to give an unbalanced chromosome arrangement?
Adjacent 1-non-homologous centromeres move together.
What is a Robertsonian translocation?
Structural chromosome abnormality resulting from fusion of 2 acrocentric chromosomes.
What won’t microarray comparative genomic hybridisation detect?
Balanced re-arrangments.
What is the most common cause of uniparental disomy?
Trisomy rescue- non-disjunction in meiosis followed by mitotic error post-fertilisation.
What type of chromosomes does uniparental disomy need to involve to have a phenotypic effect?
Imprinted chromosomes- need biparental inheritance.
