Chromosomes and Inheritance

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Chromosomes and Inheritance
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Chromosomes

• Made of DNA which makes up the genes for
  heredity.
• Two types
• Autosomes
• Sex Chromosomes

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Sex Chromosomes

• Determine the sex of the individual.
• Two types
• X chromosome
• Y chromosome

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X and Y

• Named because of appearance.
• Females have 2 X chromosomes, males have one X
  and one Y.

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How is Sex Determined?

• Presence of a Y chromosome is what makes a male
  male.
• If there was no Y, all organisms would be female.
• Therefore, the Y chromosome determines sex.

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Normal Male and Female

• Normal male indicated 46XY
• Sperm cell 23Y (50) or 23X (50)
• Normal female indicated 46XX
• Egg cell 23X

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Male vs. Female

• Draw a Punnet square indicating the sex of
  offspring.

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5050

• The chances of getting a male or a female are
  50.
• This is because each sperm cell has the same
  chance of carrying X or Y.

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5050

• The chances of getting a male or a female are
  50.
• This is because each sperm cell has the same
  chance of carrying X or Y.

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Its Twins

• If 2 eggs are released during ovulation and they
  are both fertilized, fraternal twins will be
  born.
• Identical twins are the result of a single egg
  dividing and separating after fertilization

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Gene Linkage

• Genes are said to be linked when they are on the
  same chromosome.
• Sex linked
• X linked
• Y linked

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Genes That Stay Together...

• Since linked genes are on the same chromosome
  they are inherited together.

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Unless

• If crossing over occurs in meiosis, it is
  possible that linked genes may become separated.
• Genes are not changed just rearranged.

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Crossing Over

• Aids in maintaining genetic diversity.
• This is one explanation for offspring that dont
  follow Mendels rules.

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Mutations

• Change in the DNA or chromosomes of a cell.
• Lethal mutations cause death.
• Not all mutations are bad.

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Mutations

• Change in the DNA or chromosomes of a cell.
• Lethal mutations cause death.
• Not all mutations are bad.

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Types of Mutations

• Chromosome Mutations change in the structure,
  addition or loss.
• Gene Mutations change in the bases of DNA.

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Chromosome Mutations

• Deletion part of the chromosome is missing.
• Insertion a piece of DNA is added.
• Inversion a piece of DNA breaks off and is put
  back in the reverse order.

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Chromosome Mutations

• Translocation piece of one chromosome breaks
  off and attaches to a different one.
• Nondisjunction chromosomes dont separate
  during meiosis.

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Deletion
Insertion
Inversion
Translocation
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Gene Mutations

• Point mutations one nucleotide is affected.
• 3 types
• Substitution
• Deletion
• Insertion

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Substitutions

• Result when one nucleotide is replaced with a
  different one.
• May not have any effect on the protein produced.

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Insertions

• Result when an additional nucleotide is put in
  the sequence.
• A frame shift mutation occurs which affects all
  codons after the mutation.

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Deletions

• Result when a nucleotide is added to the
  sequence.
• A frame shift mutation occurs which affects all
  codons after the mutation.

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Frame Shift Mutations

• Insertion or Deletion causes all of the codons
  after to change.
• Different amino acids are coded for and the wrong
  protein is made.

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Deletion
Substitution
Insertion