Sexlinked Traits, Sex influenced traits, etc

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Sex-linked Traits, Sex influenced traits, etc
Hairy ear-caused by a GENE located on the Y
chromosome
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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 and b is hairy then
• Men must be bb to keep hair
• Women can be Bb or bb to keep hair

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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?
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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

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How A Sex-linked trait is passedEx. 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?
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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 ?
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X-linked genes are on the X chromosome
Hemophilia gene
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Autosomal genes-NOT on the X or Y chromosomes
Dwarfism gene-on many locations
but NOT the X or Y
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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?
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Multifactorial and polygenic traits

• Polygenic-more than one pair of alleles
  determines phenotype- -eye color
• Multifactorial-genes AND environment determine
  phenotype weight and height

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Epistasis

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

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