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Cytogenetics = cellular genetics - Coggle Diagram
Cytogenetics = cellular genetics
Basic structure of a chromosome
Metacentric
Centromere near the
middle
. p & q arms of similar size
Sub-metacentric
Centromere is
closer to one end,
giving a smaller p arm & a larger q arm
Acrocentric
Centromere at
top.
Very small p arms & often have satellites (NOR region) on end
Telocentric
Centromere at end with no p arm (not present in human karyotype)
Overview of harvest procedures
Hypotonic solution
Prefixation
Fixation
Optimum harvest time
Cells are required to be actively dividing & preferably during metaphase or prometaphase
Human tissues have a cell cycle time of approx. 16 - 20 hours
Bloods usually culture for 3 days (72 hour cultures) but can range from 24 - 96 hours
Bone marrows harvested after 1 to 4 days
Tissues grown on substrate may take 5 - 30 days to produce enough cells (Prenatal tissues will usually stop growing after ~ 50 division)
Overview of basic banding techniques used
Conventional banding
Requires tissue culture to obtain actively dividing cells for chromosome capture
Molecular bands (FISH)
Can be performed on uncultured or cultured cells
Define cytogenetics
Study of genetic material at the cellular level: study of chromosomes
Chromosomes best studied at metaphase, although some studies e.g. fluorescence in situ hybridisation (FISH may utilise interphase cells)
Whole genome analysis for the diagnosis of cytogenetic abnormalities (5Mb resolution)
Prenatal investigations
Constitutional studies
Infertility/recurrent fetal loss
Spontaneous miscarriage
Leukaemia
Solid tumour & lymphoma evaluation
Identify a range of cytogenetic abnormalities
Numerical
Number of chromosomes varies from 46. Aneuploid e.g. Down, Turner, Klinefelter
Structural
Structure of one or more of the chromosomes has altered e.g. inv, dup, del, ins
Risk factors
Low copy repeats
High copy repeats
DNA hot spots
Assess the potential for genetic disease
Use for Cytogenetic analysis