Chapter 15 The Chromosomal Basis of Inheritance

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Chapter 15 The Chromosomal Basis of
Inheritance
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Timeline
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Sutton
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Morgan
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Fruit Fly
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Life Cycle

• Egg
• Larva
• Pupa
• Adult

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Reasons
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Fruit Fly Chromosomes
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Genetic Symbols
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Examples

• Recessive mutation
• w white eyes
• w red eyes
• Dominant Mutation
• Cy Curly wings
• Cy Normal wings

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Morgan Observed
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Morgan crossed
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The F1 offspring

• All had red eyes.
• This suggests that white eyes is a genetic
  _________?

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F1 X F1 F2
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Morgan discovered
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Fruit Fly Chromosomes
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Morgan Discovered
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Linked Genes
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Body Color and Wing type
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Example

• bb vgvg X bb vgvg
• (b linked to vg)
• (b linked to vg)
• If unlinked 1111 ratio.
• If linked ratio will be altered.

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Crossing-Over
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If Genes are Linked
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Linkage Strength
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Genetic Maps
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• Comment - only good for genes that are within 50
  map units of each other. Why?

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Genetic Maps
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Sex Linkage in Biology
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Chromosomal Basis of Sex in Humans
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Human Chromosome Sex
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SRY
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Sex Linkage
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Males
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X-linked Disorders
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Samples of X-linked patterns
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X-linked Patterns
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Comment

• Watch how questions with sex linkage are phrased
• Chance of children?
• Chance of males?

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Can Females be color-blind?
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Y-linkage
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Sex Limited Traits
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Sex Influenced Traits
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Baldness
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Barr Body
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Lyon Hypothesis
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Examples
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Calico Cats

• XB black fur
• XO orange fur
• Calico is heterozygous, XB XO.

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Question?

• Why dont you find many calico males?

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Chromosomal Alterations
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Number Alterations
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Aneuploidy
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Comment
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Types of Aneuoploidy
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Turner Syndrome
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Characteristics
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Question

• Why are Turner Individuals usually sterile

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Other Sex Chromosome changes
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Kleinfelter Syndrome
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George Washington

• May have been a Kleinfelter Syndrome individual.
• Much taller than average.
• Produced no children.

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Meta female
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Super male
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Trisomy events
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Question?

• Why is trisomy more common than monosomy?

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Question?

• Why is trisomy 21 more common in older mothers?

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Polyploid
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Question?

• In plants, even polyploids are often fertile,
  why odd polyploids are sterile. Why?

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Structure Alterations
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Result
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Translocations
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Cri Du Chat Syndrome
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Philadelphia Chromosome
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Parental Imprinting of Genes
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Example
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Cause
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Result
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Why have parental imprinting?

• Method to detect that TWO different sets of
  chromosomes are in the zygote.

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Experiment

• Can fuse nuclei into mouse eggs.
• If male/male normal placenta, abnormal fetus
• If female/female abnormal placenta, normal
  fetus
• If male/female normal placenta and normal fetus

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Extranuclear Inheritance
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Result
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Mitochondria
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Chloroplasts
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Variegated Examples
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Variegation in African Violets
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Comment

• Cells can have a mixture of normal and abnormal
  organelles.
• Result - degree of expression of the maternal
  inherited trait can vary widely.

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Summary

• Know about linkage and crossing-over.
• Sex chromosomes and their pattern of inheritance.
• Variations of chromosomes and inheritance
  patterns.

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Summary

• Be able to work genetics problems for this
  chapter.