CHANGES IN THE GENETIC CODE

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CHANGES IN THE GENETIC CODE
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Ectrodactyly
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• What do they all have in common?
• Theyre all mutations!

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MUTATIONS

• a change in the DNA code
• causes a different (sometimes wrong) type of
  protein to be made
• may or may not be good for the organism

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ALONG THE WAY

• good changes occur
• bad changes occur
• changes that dont matter either way

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CHANGE IS NECESSARY

• without changes we would all look alike
• without changes we would not evolve
• without changes we would not develop immunities
  to disease
• SO Is change/variation a good thing???
• YES!

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Causes of Variation

• Crossing Over
• Mutations
• Some happen randomly
• Some caused by Mutagens (agents that cause
  mutations)
• Nuclear Radiation
• Ultraviolet Light
• X Rays
• http//learn.genetics.utah.edu/units/disorders/slo
  ozeworm/mutationbg.cfm

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CROSSING OVER

• occurs when homologous chromosomes trade segments
• occurs during Prophase I of Meiosis

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• entire gene is switched
• involves the variation of a single trait
• gene for big ears exchanges with gene for small
  ears

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Advantages

• variation of offspring from parents
• allows for good changes
• Better chance of passing on genes for survival

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3 TYPES OF MUTATIONS

• Chromosomal mutations
• Gene mutations
• Somatic mutations
• these usually occur during mitosis and involve a
  chromosomal mutation
• involved with body cells, not sex cells
• tumors are the result

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Research your mutation

• 1. Answer these questions
• What does the name of the mutation mean?
• What happens to the chromosome?
• What is an example?

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CHROMOSOMAL MUTATIONS

• NONDISJUNCTION
• DELETION
• INVERSION
• DUPLICATION
• TRANSLOCATION
• INSERTION

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NONDISJUNCTION

• failure of homologous pairs to separate during
  meiosis
• correct number of chromosomes are not present in
  the gamete
• after fertilization, diploid number is not
  restored

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Examples

• Trisomy 21(Down Syndrome)- 3 copies of
  chromosome 21
• Klinefelters Syndrome- XXY
• Turner Syndrome- X
• Supermales - XYY

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DELETION
A SEGMENT OF A CHROMOSOME IS DELETED
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Examples

• Cri-du-chat syndrome- cry of the cat- deletion
  of piece of chromosome 5
• Angelman Syndrome- deletion of piece of
  chromosome 15
• Prader-Willi Syndrome- deletion of piece of
  chromosome 15

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INVERSION
A SEGMENT OF THE CHROMOSOME IS FLIPPED IN THE
OPPOSITE DIRECTION
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DUPLICATION
A SEGMENT OF THE CHROMOSOME IS COPIED TWICE
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TRANSLOCATION
SEGMENTS FROM TWO DIFFERENT CHROMOSOMES ARE
SWITCHED
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Example

• Translocation Down Syndrome
• Instead of being 3 separate copies of chromosome
  21, the extra copy is actually attached to
  another chromosome

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INSERTION
A SEGMENT OF ONE CHROMOSOME IS INSERTED INTO A
DIFFERENT CHROMOSOME
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GENE MUTATIONS

• POINT MUTATIONS
• FRAME SHIFT
• insertions
• deletions
• INVERSIONS

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LETS MUTATE!

• Start with an original strand of DNA
• GCC TTA CGT TTA CGA CTG TAC GTA
• CGG AAT GCA AAT GCT GAC ATG CAT
• A B C D
• lets assume this strand codes for a protein

AMINO ACIDS
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POINT MUTATIONS

• TTA CGT TTA CGA
• AAT GCA AAT GCT ORIGINAL
• 1 base is replaced with another base
• TTA CTT TTA CGA
• AAT GAA AAT GCT MUTATION

B
E
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Example

• Sickle Cell Anemia- changing 1 base causes
  mutation that codes for valine instead of
  glutamate in the protein hemoglobin
• Individuals produce different type of hemoglobin
• Red Blood Cells become sickle shaped and dont
  pass thru blood vessels as easily
• Cells die sooner than normal
• Individuals dont get as much oxygen

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• http//www.montgomerycollege.edu/wolexik/Sickle2
  0Cell20Anemia20400x.jpg

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FRAME SHIFTS

• TTA CGT TTA CGA
• AAT GCA AAT GCT ORIGINAL
• A B C D
• TTA CGT TTA ACG A
• AAT GCA AAT TGC T INSERTION-base is
  inserted
• A B C F
• TTA CGT TAC GA
• AAT GCA ATG CT DELETION- base is deleted
• A B G

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INVERSIONS

• TTA CGT TTA CGA
• AAT GCA AAT GCT ORIGINAL
• A B C D
• Codon is found in reverse order
• TTA TGC TTA CGA
• AAT ACG AAT GCT INVERSION
• A H C D

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Consequences

• Sometimes mutations are bad and cause for
  different proteins to be made
• But- if you look at the amino acid chart- several
  different codons code for the same amino acids
• Mutations can occur but wouldnt be noticed
• Some mutations are masked by other genes