Cytogenetics = cellular genetics

Basic structure of a chromosome

Overview of harvest procedures

Overview of basic banding techniques used

Conventional banding

Molecular bands (FISH)

Define cytogenetics

Identify a range of cytogenetic abnormalities

Numerical

Structural

Assess the potential for genetic disease

Use for Cytogenetic analysis

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

Metacentric

Sub-metacentric

Centromere is closer to one end, giving a smaller p arm & a larger q arm

Centromere near the middle. p & q arms of similar size

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)

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)

Requires tissue culture to obtain actively dividing cells for chromosome capture

Can be performed on uncultured or cultured cells

Number of chromosomes varies from 46. Aneuploid e.g. Down, Turner, Klinefelter

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