... The most convincing evidence [about the individuality of the chromosomes] comes from exceptional cases of accidental or irregular distribution of one or more chromosomes, so that an egg, or a cell comes to have one more chromosome than is usually present...
- Thomas Hunt Morgan,
The Physical Basis of Heredity,
1919, page 52
Perhaps a better title for today's lecture would be:
This poor fly has lost its X chromosome after the 2nd cell division - so it is literally half male (X0) and half female (XX). Several sex-linked traits that would otherwise have been masked are now visible in half of this fly! (Most sexual mosaics are called gynandromorphs.)
Yes, the same thing can happen in humans!
There are two different types of variation in chromosome number:
2. Aneuploidy -this is where you have an extra single chromosome (or two) or are missing a chromosome (or two)
I. Aberrant Euploidy
Polyploidy in Animals
Last modified on: 1 February, 2000 by Dave Ussery