Cytogenetics Flashcards
What is the X inactivation and what is the resulting pattern?
Inactivation of the chromosome X of Paternal or Maternal randomly in different cells in the female offspring. Functional Mosaicism is the resulting pattern.
What is the form retained in granulocytes by the Inactive X?
Barr Bodies
What is the utility in finding the Barr body?
Checking for chromosomal abrasions and Proof of female sex in an individual.
How can we find the Y body? Why?
Brilliant Fluorescence
It is a very condensed one and it has a natural autofluorescence.
What are the direct and Indirect ways to prepare for chromosome detection?
Direct - Simply looking for a dividing cell in the smear, not probable
Indirect - In vitro stimulation to get to metaphase and stopping it there.
How can we isolate the chromosomes in metaphase from the cells for microscopic preparation? 3 general steps
Centrifugation for concentration and later adding a low salt solution for elimination of cells. Staining with Giesma.
Parts of the Chromosome (3 important ones)
p - Short arm
q - Long arm
Centromere
What is Karyotyping? Checking for?
Length of Chromosome
Structure of Chromosome
Karyogram Vs Karyotype Vs Idiogram
Karyogram - From one cell
Karyotype - From one species
Ideograms - 150 human samples
Grouping of Chromosomes according to arm ratio
Metacentric Chromosome
Centromere in the middle
p=q
Grouping of Chromosomes according to arm ratio
Submetcentric Chromosome
p is a bit smaller than q
Grouping of Chromosomes according to arm ratio
Acrocentric Chromosome
p is much smaller than q
Grouping of Chromosomes according to arm ratio
Telocentric Chromosome
p=0
q»>
(Not found in human)
What is the NOR?
Nucleolar organizer region
These are repetitive rDNA - rRNA genes
What is the staining used for investigation of Chromosomes? The basic one
Giesma Stain
G-Banding - Giesma with SAR attachment -
What will appear dark?
A and T rich regions
G-Banding - Giesma with SAR attachment -
What will appear light?
G-C rich regions
What is the state of the cell that allows us to check for the Barr bodies?
Interphase
No need to special preparation - Barr bodies are large enough to be recognized in granulocytes
How many regions are in each arm of the chromosome?
2
Meaning if we get a location of a gene in q13 than 1 will be the region in the long arm
In a gene located in q13. What is the meaning of 3?
Band
In a gene located in p11.4. What is the meaning of 4?
Sub-Band
What does it mean if a chromosome is qh positive?
Excess of centric heterochromatin in the long arm- chromosome polymorphism.
FISH - Initials
Fluorescence In-Situ Hybridization
FISH
4 Steps
1 - Denaturation
2 - Hybridization with small labeling molecules (per sequence)
3 - Fluorochrome labeled Antibodies bind to the labeling molecules
4 - Epifluorescence Microscopy - Location of gene measured