Chromosomes - Terminology and Isolation

Short Hand
Description
p Short arm of a chromosome
q Long arm of a chromosome
p+/-, q+/- Addition/subtration of chromosomal material from the short/long arm
del Deletion
dic Dicentric (two centromeres) chromosome
+/- Addition/subtraction of a chromosome
Aneuploid Cells with an unusual no. chromosomes that is not half or a multiple of 46
Diploid Cells with the normal number of chromosomes (23 pairs = 46)
Haploid Cells with 23 unpaired chromosomes
Tetraploid Cells having 92 chromsomes (4x normal=46 pairs)
Karyotype Ordered array of the chromosomes of a cell (or a clone of cells ie. individual)
Centromere Intersection of the short and long arms of a chromosome
Paracentric inversion Inversion of a segment of a chromosome restricted to one arm
Pericentric inversion Inversion of a segment of a chromosome involving part of both arms and the centromere

Preparation

  • Lymphocytes can be extracted and stimulated to undergo mitosis in culture
  • The best stage to study the cells in is metaphase
  • Cells are frozen or treated with chemicals to arrest division during this stage
  • Chromosomes (seen as 2 chromatids) are released from the cells and swelled by the addition of a hypotonic solution
  • Chromosomes are stained with Giemsa to increase the visibility of the banding patterns
  • The centromere (primary constriction) is seen as a non-staning area in the center of the chromosome
  • Lighter or non-staining areas (secondary constricitons) are seen along the chromatid arms
  • Satellites are visible on the distal ends of the short arms of some chromosomes


New look for June 2003