AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

KARYOTYPE AND IDEOGRAM

Karyotype

• The general morphology (size of chromosomes, position of centromere, presence of secondary constriction and size of satellite bodies) of somatic chromosomal complement of an individual constitutes its karyotype.
• In a karyotype, chromosomes are arranged and numbered by size, from largest to smallest.
• The karyotype of a normal somatic cell of a normal individual represents the karyotype of the concerned species.
• This arrangement helps scientists quickly identify chromosomal alterations that may result in a genetic disorder.
• To make a karyotype, picture of someone's chromosomes taken, cut them out and match them up using size, banding pattern and centromere position as guides.
• Avian karyotype is different from mammalian karyotype because of presence of very small autosomes called microchromosomes.

Ideogram

• The karyotype of a species can be represented diagrammatically showing all the morphological features of chromosomes. Such a diagram is known as ideogram or ideotype.