Diff. between female and male chromosomes?

[ROGER GREEN,MEDICINE,ST.JOHN'S,NF,CAN]

In article <sjj.32.0008A309 at srcros1.pathology.ufl.edu>, sjj at srcros1.pathology.ufl.edu (Song-Muh Jong) writes:
> I used to have an impression that human chromosomes are the simple 23 pairs. 
> However, the linkage maps of human chromosomes indicate that female maps are 
> larger than male maps. Can someone explain this phenomenon?
> Song-Muh Jong                     TEL: (904) 392-0011

	This is simply a consequence of the fact that during meiosis in a 
female (i.e. ovum production), the rate of recombination (crossing over) 
between homologous pairs of chromosomes is greater than the rate during 
meiosis in a male (during spermatogenesis).  
	In linkage maps, map distance is a function of the rate of 
recombination between loci on the map. Thus female map distances are 
"longer".

Roger C. Green,	Faculty of Medicine               Phone: (709)737-6884
Memorial University , St. John's, Newfoundland    FAX  : (709)737-7010