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

Creighton and McClintock experiment

CREIGHTON AND McCLINTOCK'S - LINKAGE IN MAIZE

• Creighton and McClintock worked with a strain of maize and developed a strain with a knob on one end and extra (translocated) piece of chromosome at the other end of the 9^th chromosome .
• This knobbed chromosome was thus clearly different from its normal homologue.
• This knobbed chromosome had one dominant gene for coloured kernel (C) allele and the another gene for recessive waxy texture endosperm (wx) allele.
• This strain was crossed with a plant having normal chromosome with colourless (c) and starchy (Wx) phenotype.
• When the off spring examined, they found crossing over occurrence by visible cytological observations causing the knob to become associated with an otherwise normal chromosome and the extra piece of chromosome to be associated with a knobless chromosome.