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Key Concepts

In diploid organisms chromosomes are found in pairs. This is particularly obvious during meiotic division, when the pairs of chromosomes come together in Prophase I.

    Key concepts:
  • A karyotype of a diploid organism shows that most chromosomes come in almost identical pairs.
  • Both partners in a pair have the same length, the same centromere position, and the same pattern of bands (caused by the different stains or dyes).
  • Such a pair of chromosomes are said to be homologues of one another.
  • Each homologue carries the same pattern of genes in the same locations (called "loci") along its length, essentially they are duplicates of the same genetic information.
  • However, in any one individual, the exact sequence of the nucleotide bases along the DNA of each gene may not be completely the same. They could be identical, slightly different, or grossly different (as in a mutation).
  • Thus, sister chromatids, which are exact DNA copies of the genetic information on one chromosome, are NOT the same as homologues!

Science@a Distance
© 2001, Professor John Blamire