Clinical Genetics (Diagnostics L1)

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  • Created by: Hpgrice
  • Created on: 29-10-19 17:54

What is cyto-genetics?

  • Chromosome Analysis
  • FISH test e.g. TBX1 gene in Chromosome 22 for Di George syndrome (most common microdeletion syndrome in the world)
  • MLPA - Multiplexing PCR so mutliple tests can be ran on the same sampel
  • Quatitative Fluorescent-PCR
  • array CGH/SNP array

Cyto-genetics resolution is 5Mb and usually used cell culture and microscopy where as molecular genetics is 1bp and used DNA extraction and PCR.

Primary tissues for testing: blood, bone marrow, amniotic fluid, chorionic villus biopsies, skin biopsies.

37'C incubator,  media that includes nutirents required and growth factors. For blood PHA which stimulates T-cells. Then add  Colcemid (derived from kidney beans) to stop cell division at metaphase. The cells are then processed and the suspension is put onto a slide to view under the microscope or use a slide scanner which finds 120 metaphases per patient which reduces time.

Chromosome Classification

Short arm = p (petit) and long arm = q

1.Metacentric - p arm and q arm are approx the same length e.g chromosomes 1,3,16,19 & 20

2. Sub-metacentric - p arm shorter than q arm e.g 4,5,17,18, most others

3. Acrocentric - satellite structure present on p arm, p arm very small e.g 13,14,15,21,22

X and Y are sex chromosomes, all others are autosomes

Giemsa Banding

  • Pre-treatment with proteolytic enzyme trypsin
  • Dark bands…

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