CHANGES IN DNA CAN PRODUCE VARIATIONS

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CHANGES IN DNA CAN PRODUCE VARIATIONS

• DNA sequences can change (mutation)
• Mutations can cause genetic disorders (like
  sickle cell anemia cystic fibrosis)
• Cancer is a genetic disorder that affects the
  cell cycle

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DNA sequence can change

• Each human cell, with 46 chromosomes, has 6
  billion base pairs in its DNA.
• 99.9 of DNA in cells of 2 different humans is
  same. Just 0.1 variation in DNA makes you unique
  different from others. (about 1 base in every
  thousand).
• Only 5 of the billions of base pairs of DNA are
  in the GENES that code for RNA and proteins

Differences in genes affect height, color of
eyes, hair, skin, etc. Skin color comes from
protein (melanin). The more melanin their skin
cells are programmed to make, the darker their
skin color
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DNA sequence can change

• Exposure to ultraviolet radiation, x-rays,
  toxins can damage DNA. Any change in DNA is
  called a MUTATION.
• Cells have different ways to repair mistakes
  (through enzymes).
• If a mutation occurs in a gene (the 5 of DNA
  thats the coding region) the wrong amino acid
  may be placed in the amino-acid chain.

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3 possible outcomes if mutation occurs in a gene
(coding region)

• MUTATION CAUSES NO EFFECT there are 2 sets of
  DNA (1 from each parent) so if 1 gene isnt
  working, the other may still code for enough of
  the protein to let the cell function normally

• EFFECT OF MUTATION IS MINOR a change in the
  genes may only produce a slight change in
  appearance (the amount of melanin produced for
  skin or hair color)

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Possible outcome if mutation occurs in coding
region of DNA

• EFFECT OF MUTATION IS GREAT can be good (plant
  has increased resistance to disease) or bad,
  causing genetic disorder or disease.
• If mutation occurs in the 95 of DNA that doesnt
  code , no effect will occur it is neutral

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MUTATIONS CAN CAUSE GENETIC DISORDERS

• Genetic disorder results from mutations that
  affect the normal functioning of a cell.
• Some are inherited (passed on from parent to
  offspring like Tay-Sachs, Sickle-cell , and
  cystic fibrosis)
• Others are results from mutations within a
  persons own lifetime (cancers)
• Sometimes a tendency for getting a disease
  (like diabetes, glaucoma, alzheimers) is
  inherited and a persons behavior can bring on or
  prevent the disease.

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GENETIC DISORDERS

• Sickle Cell disease occurs from a mutation where
  one amino acid is replaced by another. Since it
  is recessive, both alleles must be inherited to
  cause it (abnormally shaped red blood cell
  decreasing oxygen and damaging tissue).
• Sickle cell protects against malaria, so allows
  people to survive with it and pass it on (occurs
  in Africa, parts of India and Middle East).
• A PEDIGREE (diagram of family relationships that
  include 2 or more generations) can show how the
  sickle cell allele is passed on through
  generations of a family.

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Cancer is a genetic disorder that affects the
cell cycle

• Cancer is a group of disorders, all characterized
  by uncontrolled division of cells.
• Cancer cells spread quickly invade other
  tissues become immortal dividing indefinitely-
  while normal cells have a definite life span and
  die.
• Most cancers due to mutations to DNA over a
  persons life. Some from mistakes during
  replication, but many from harmful chemicals
  (carcinogens).
• Cancer involves series of mutations some people
  inherit 1 step in the series or a tendency for
  it.