Chromosomal Abnormalities Flashcards
What is trisomy?
extra copies of a chromosome
What is monosomy?
A diploid chromosome complement where one lacks its homologous partner
What is triploidy & teroploidy?
Triploidy - extra set of chromosomes (total 69)
Tetraploidy - 2 extra sets of chromosomes (total 92)
How do numerical abnormalities mainly arise?
When chromosmes dont divide properly during meiosis (non-junction)
What is another name for trisomy 21?
Downs syndrome = Trisomy 21
What are characteristics of trisomy 21?
Maternal (chances increase with age)
Distinc facial characteristics
Alzhiemers in later life
IQ < 50
50-60 yr life expectancy.
What is Trisomy 13 called?
Patau Syndrome = Trisomy 13
Characteristics of trisomy 13?
Mental retardation
Dysmorphic features
Maternal
Most die in 1st year
What is Trisomy 18 called?
Edwards Syndrome = Trisomy 18
Characteristics of Trisomy 18
Severe developmental abnormalities
Most die in first month or year of life
What is Turner syndrome?
45,X
Lack of a sex chromosome from father
What are characteristics of 45,X (turners syndrome)?
- Short stature & infertile
- All female
- Neck webbing & widely spaced nipples
- 97% die at conception
What is 47, XXY called?
Klinefelter Syndrome = 47,XXY
What are characteristics of Klinefelter syndrome?
- Tall & long limbed
- Infertile, small testes
- 50% develop breasts (gynaecomastia)
- Mild learning difficulties.
What is a balanced translocation?
Non-Homologous Chromosomes break and repair with some DNA swapped
Usually fine since all DNA is present.