d. Multiple Alleles

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d. Multiple Alleles Instead of having two forms
of an allele, there are more than two for one
gene.

• i. The best example for humans is blood. There 3
  alleles for blood types in humans A, B and O. A
  and B are co dominant while O is recessive.

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Multiple Alleles Blood Type

• Type A genotypes could be IAIA or IAi.
• Type B genotypes could be IBIB or IBi.
• Type AB genotype is IAIB
• Type O genotype is ii

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Practice

• A man who is heterozygous for type A blood
  marries a woman who is heterozygous for type B
  blood. Find the possible outcomes

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e. Sex linked traits

• i. Autonomies there are 44 (22, pairs) of non
  sex chromosomes.
• ii. Sex Chromosomes the 23rd pair of
  chromosomes are the sex chromosomes.
• The genotype for females is XX the genotype for
  males is XY.

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e. Sex linked traits

• iii. Sex linked traits Are genes located on the
  X chromosome. There is almost no information
  located on the Y chromosome.
• Since males have only one X chromosome they show
  whatever allele is on the X chromosome,
  regardless of whether it is dominant or recessive.

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e. Sex linked traits

• iii. This is the only time that a single
  recessive allele is expressed.
• Two examples of sex-linked traits in humans are
  red/green colorblindness and hemophillia. (A
  recessive sex linked trait that keeps your blood
  from clotting.)

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Color Test
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Color Test
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Color Test
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Color Test
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Sex linked traits - Colorblindness

• If normal vision (N) is dominant to
  colorblindness (n) give the genotypes for each of
  the following
• A female carrier XNXn
• A homozygous dominant female XNXN
• Colorblind male XnY
• Colorblind female XnXn
• A male with normal vision XNY

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Sex linked traits

• Who does the male get the X chromosome from?
  Mother
• Who does a male inherit recessive sex linked
  traits from? Mother
• Who are colorblind more often, men or women?
  Men no information on Y to mask the recessive
  trait on X.

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Practice

• A female carrier has a child with a male with
  normal vision. What are the chances of
  colorblindness occuring in
• Son?
• Daughter?

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Practice

• A colorblind male has a child with a normal
  female. Fill out the cross.