Cytogenetics Flashcards
Autosomal Dominant allele
All males and females
Doesnt skip generation
Autosomal Recessive allele
All males and females
Can skip generations
Y linked
All males affected
Pseudoautosomal region- non sex linked inherited
Autosomal
Both females and males ( non sex)
X linked recessive
Always expressed in males, passed from mothers, daughters unaffected
X linked dominant
From fathers to daughters not sons
What is a karyotype
Numerical abnormalities in chromosomes
P arm and q arm
P= short arm
q= long arm
Trisomy karyotype
DS 47,XX,+21
Edwards +18
Pataus +13
Aneuploidy and polyploidy
A- Monosomy X
p- extra haplet (23)
4 chromosomal abnormalities
Turners 46, XO
Trisomy X 47, XXX
Klinefelters 47,XXY
Extra “Y” chromsome 47,XYY
Robertsinion and Reciprical
Robertsinian-Deletion of short arm - long arms join together
Acrocentric
Recipricol- occurs within chromosome
Metro centric
Meiosis 1 and 2
1- homologous chromosomes pairing
2-sister chromatids pairing
FISH
Analysis of small chromosomal regions of cells at interphase
Types of arrays
CGH- loss and gain
SNP- recombination sites
Different staining methods
G banding- giemsa
Q banding- quinacrine
R Banding - reverse
C banding- centrometric (heterochromatin)
What phase of cell cycle is needed at karyotype
Metaphase
Colchicine arrest cells in metaphase to prevent mitotic spindle formation
What is g banding
Most common method
Chromosome treated with trypsin to denature protein
Dark and light bands
Dark- gene poor
Light- gene rich
Q banding
Y chromosome abnormalities
Polymorphism
Fluorescence microscope
R banding
To detect X chromosome abnormalities
Heat chromosome before stains
Reversed light and dark bands
C banding
To identify centromere/ heterochromatin
Contain repeated sequenced and highly condensed chromatin fibres
Chr treated with acid, alkali then G band
What is isochromasome
Two copies of the same arm
Esac
Extra structurally abnormal chromosomes, abnormal
