52 Genetics since Mendel

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5-2 Genetics since Mendel
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Incomplete Dominance

• Incomplete dominance is when the offspring
  phenotype of two homozygous parents is in between
  the parents.
• Four oclock plant red flower and white flower
  parents produce pink flowered offspring.

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Multiple Alleles

• Multiple alleles are when there are more than two
  alleles for one trait.
• Traits controlled by multiple alleles show more
  than three phenotypes.
• With only three alleles there are six different
  combinations of alleles possible.
• Blood type is one example of multiple alleles

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Polygenic Inheritance

• Polygenic inheritance is when there are several
  gene pairs that control a trait.
• Eye color and height are examples of polygenic
  traits.
• Polygenic traits usually show a range of
  phenotypes.

5
Impact of Environment

• Your environment can effect if or how genes are
  expressed.
• Some genes such as cancer genes can be activated
  by things in the environment.

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Human genes and Mutations

• If a mutation in a gene causes a trait to be
  expressed differently.
• Not all mutations are bad.
• Certain chemicals, x-rays, and radioactive
  materials can all cause mutations.

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Chromosome Disorders

• The wrong number of chromosomes is a mutation
  that cause problems.
• The wrong number of chromosomes is usually fatal
  to the unborn fetus

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Recessive genetic disorders

• Many diseases are caused by recessive alleles.
• Both parents need to have one of the recessive
  alleles.

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Sex Linked disorders

• If a genetic disorder is carried on one of the
  sex chromosomes.
• Sex linked disorders affect males more often than
  women.
• For a woman to have get a recessive disorder both
  parents have to have one allele

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Pedigrees trace traits

• A pedigree is a visual tool for following a trait
  through many generations.
• Filled shapes are individuals with the trait.
• Half filled shapes are individuals that are
  carriers for a trait
• Shapes without any color dont have the trait and
  dont carry the allele for the trait.

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Using Pedigrees

• Looking at a pedigree can help a scientist
  determine what type of inheritance patterns are
  at work.
• Pedigrees are used in breeding animals to show
  the purity of the animals heritage.