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Sex-linked Traits, Sex influenced traits, etc

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Sex influenced traits The gene is NOT on a sex chromosome, but SEX affects the phenotype Ex-baldness-dominant in males, recessive in women If B represents bald ... – PowerPoint PPT presentation

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Title: Sex-linked Traits, Sex influenced traits, etc


1
Sex-linked Traits, Sex influenced traits, etc
Hairy ear-caused by a GENE located on the Y
chromosome
2
Sex influenced traits
  • The gene is NOT on a sex chromosome, but SEX
    affects the phenotype
  • Ex-baldness-dominant in males, recessive in women
  • If B represents bald and b is hairy then
  • Men must be bb to keep hair
  • Women can be Bb or bb to keep hair

3
Sex-Linked
  • Caused by a gene that is located on a SEX
    chromosome (X or Y)
  • Most SEX-linked Traits are found on the X
    chromosome

Can females get hairy ear?
4
X-linked diseases
  • Most are recessive
  • Examples-hemophilia, red-green colorblindness
  • Males are more likely to have these because they
    cannot be carriers
  • Why?
  • Males are XY-if their X has a bad gene, there
    is nothing on the Y to dominate over it

5
How A Sex-linked trait is passed Ex. Red-Green
Colorblindness (x-recessive)
  • N
  • n
  • XNXNNormal
  • XNXnCARRIER, but IS NOT colorblind
  • XNYNormal
  • XnYHAS red-green colorblindess

X
normal X
X
X with red-green cblind gene
Y
no equivalent
What sex is most commonly affected by SEX-linked
traits?
6
Passing colorblindness
  • Carrier mom XNXn
  • Normal Dad XNY
  • XN Xn
  • XN XNXN XNXn
  • Y XNY XnY

Chances of a colorblind Daughter?
Colorblind son?
What of their sons will be colorblind?
genotype ratio 1111
Phenotype ratio ?
7
X-linked genes are on the X chromosome
Hemophilia gene
8
Autosomal genes-NOT on the X or Y chromosomes
Dwarfism gene-on many locations
but NOT the X or Y
9
Other X-linked traits
  • Orange and Black Alleles are on the X chromosome
    in cats
  • White is on another chromosome
  • In every cell, only 1 X chromosome is active
    (other X is Barr Body)
  • Result-some cells make black fur, some orange

A calico cat is ALWAYS what sex?
10
Multifactorial and polygenic traits
  • Polygenic-more than one pair of alleles
    determines phenotype- -eye color
  • Multifactorial-genes AND environment determine
    phenotype weight and height

11
Epistasis
  • Multiple alleles (more than 2 involved)
  • One allele causes the other to act differently)
  • Example-E is brown unless B is present

12
(No Transcript)
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