AP Biology
Sex Linked Traits
AP Biology
Sex linked traits Genes are on sex chromosomes (pair 23)
as opposed to autosomal chromosomes
AP Biology
Genes on sex chromosomes
Y chromosome few genes other than SRY
SRY - Sex-determining Region of Y turns on genes for production of male hormones
X chromosome other genes/traits beyond sex determination
AP Biology
RR rr
You would think this right?
x
r r
R
R
Rr
Rr Rr
Rr
100% red eyes
Rr Rr
x
R r
R
r
RR
Rr rr
Rr
3 red : 1 white
Doesn’t workthat way!
AP Biology
XRXR XrY
But it’s not normal dominance…its sex-linked
x
Xr Y
XR
100% red eyes
XR
XRXr XRY
XRYXRXr
x
XRXr XRY
XR Y
XR
Xr
XRXr
XRYXRXR
XrY100% red females50% red males; 50% white males
AP Biology
Hemophilia
Hh x HHXHYXHXh
XHXh
XH
Xh
XHY
Y
XH
sex-linked recessive
XH Ymale / sperm
XH
Xh
fem
ale
/ eg
gs XHXH
XHXh
XHY
XhY
XHXH XHY
XHXh XhY
carrier disease
AP Biology
Colorblindness
Hh x HHXHYXHXh
sex-linked recessive
XH Ymale / sperm
XH
Xh
fem
ale
/ eg
gs XHXH
XHXh
XHY
XhY
XHXH XHY
XHXh XhY
carrier disease
AP Biology
What about
Baldness?
Great!!!!
Any Questions?