The Y Chromosome*PAR - Pseudoautosomal region*MSY – Male-specific region of Y

*SRY – Sex determining region*TDF - Testis Determining

Factor

Is the Y chromosome a “genetic wasteland”?

SKALETSKY, et al. (2003) The male-specific region of the human Y chromosome is a mosaic of discrete sequence classes. Nature 423, 825 - 837

The Y Chromosome

The X Chromosome and Dosage Compensation*Do females produce twice as much of each gene product for X-linked genes?

Dosage compensation

*In mammals – X inactivation

*Barr and Bertram

*Susumo Ohno

The X Chromosome and Dosage Compensation*If you can make one copy of X (in females) inactive, you can compensate for dosage

Indirect evidence:

X Inactivation*Lyon hypothesisExample: Coat color in cats; G6PD in human fibroblasts

Avner, P. and Heard, E. (2001); X-CHROMOSOME INACTIVATION: COUNTING, CHOICE AND INITIATION, Nature Reviews Genetics 2; 59-67

Review: X inactivationMechanism of inactivation:XIC or X-inactivation center

Sex determination in Drosophila:

Sex determination in Drosophila:

Temperature and sex determination: