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?