Sex Determination and Gene Dosage

Introduction

Sex Determination

Pseudoautosomal Region – doesn’t mean much

Genetic Determination

Karyotype

Phenotype

Locus involved

46, XY

normal male

TDF (SRY) expressed (Y-linked)

46, XX

normal female

No SRY

46, XY p-:46, XY

Female

Absence of TDF (SRY)

46, XY

Female

Androgen receptor (x-linked)

46, XX

Male

Presence of TDF (SRY)

45, X

Female with amenorrhea

Ovarian maintainance

Sex Chromosome Aneuploids

X inactivation (dosage compensation)

The Timing of X Inactivation