Chromosomes and Chromosomal abnormalities Flashcards
how many chromosomes does a normal female have ?
46 XX
what arrangement is all chromosomal material present in ?
balanced chromosome rearrangement
describe unbalanced chromosome rearrangement
extra or missing chromosomal material
usuallly 1 or 3 copies of some of the genome
developmentally bad news
what is aneuploidy ?
whole extra or missing chromosome
what is translocation ?
rearrangement of chromosomes
e.g. down syndrome
what is the arrangement for down syndrome ?
47 XY + 21
what could down syndrome may be reffered to ?
trisomy 21
( because its 47 XY + 21 )
what are the chromosome arrangement for miscarriage, edward syndrome, turner syndrome and klinefelter syndrome ?
miscarriage (trisomy 14) - 47 XY + 14
edward syndrome (trisomy 18) - 47 XY + 18
turner syndrome - 45 X
klinefelter syndrome - 47 XXY
Define Robertsonian translocation
two acrocentric chromosomes stuck end to end
what does Robertsonian translocation increase risk of ?
trisomy in pregnancy
What do microarray CGH do ?
detect any missing or duplicated piece of chromosome
finds polymorphisms
How can different cells have a different genetic constitution ?
mosaic chromosome abnormality
mosaicism for a point mutation
Describe somatic mosaicism
all cells suffer mutations as they divide
repair mechanisms exist
what does gonadal mosaicism cause ?
causes recurrence risk for autosomal dominant conditions even if parent unaffected
how does cancer occur ?
mutations in cell cause damage to control genes that allow cell to divide in an uncontrolled fashion
