DNA Mutations

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DNA Mutations Disorders
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Normal Protein Formation

• A segment of DNA strand is copied by mRNA in the
  nucleus.
• mRNA leaves nucleus and goes to ribosome in
  cytoplasm.
• Ribosome reads mRNA and calls for specific
  amino acids.
• Amino acids linked together to form protein
  chain.

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Abnormal Protein Formation

• Mutations in DNA will code for wrong amino acids
  which will cause wrong protein to form.
• Can lead to cell death, disease, disorders

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What is a mutation?

• Any change in a gene or chromosome.
• Most are natural and have no effect on the
  organism- can promote good genetic diversity
• Some are harmful
• Some are lethal (cause death in offspring)
• Some are good for the organism (ex some
  mosquitoes have a gene mutation that makes them
  resistant to pesticide- leads to evolution of
  stronger mosquito populations)

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What are some types of mutations?

• Point mutation- change in ONE single nitrogen
  base in ONE gene.
• This change causes the code to change so amino
  acids are not put in correct order.
• EX albinism, sickle cell anemia

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Types of Point Mutations

• A. Silent- one letter change but no change in
  amino acid no change in protein structure no
  problems
• B. Missense- one letter change causes changed
  amino acid wrong protein structure
• C. Nonsense- one letter change causes STOP codon
  in middle of amino acid chain protein wont get
  made

(Normal)
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What are some types of mutations?

• 2. Chromosome Mutations (Frameshift)- changes in
  MANY genes, entire segments of chromosome are
  messed up.
• Because more genes are involved, usually more
  harmful to the organism.

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1. Deletion- part of chromosome is lost
2. Duplication- part of chromosome is repeated twice
3. Inversion- chromosome breaks, piece is turned
   over reinserted upside down
4. Translocation- two chromosomes affected- one
   piece detaches reattaches to another chromosome

A
B
C
D
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• E. Insertion- a nitrogen base is added which
  causes nitrogen bases to shift to the right,
  throws off amino acid sequence.
• F. Nondisjunction- a chromosome pair fails to
  separate properly during meiosis (some sperm/egg
  get too many chromosomes, some get too few).
• Monosomy- too few (45 chromosomes)
• Trisomy- too many (47 chromosomes)

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What are some causes of mutations?

• 1. Mutagen- anything that causes a mutation in
  DNA in a cell.
• UV light
• Radiation
• X rays
• chemicals in tobacco smoke, synthetic materials,
  pollution
• viruses

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What is the difference between germ cell mutation
somatic cell mutation?

• Germ Cell mutation
• Occurs in gametes (sperm/egg)
• Does not affect individual person
• CAN be passed to offspring

• Somatic Cell mutation
• Occurs in body cells
• Affects individual in which it occurs
• CANNOT be passed to offspring
• If occurs in genes that control cell reproduction
  can become CANCER.

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What are some methods of detection?

• Ultrasound- sound waves generate image of unborn
  child. Detect abnormalities of limbs, organs,
  etc.

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What are some methods of detection?

• Amniocentesis use needle to extract fluid/cells
  surrounding the fetus. Chromosomes can then be
  karyotyped

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What are some methods of detection?

• Karyotyping pictures of chromosomes are matched
  up according to size

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Difference between Autosomes Sex Chromosomes

1. Autosomes- first 22 pairs of chromosomes in
   karyotype
2. Sex Chromosomes- last pair of chromosomes that
   determine gender
3. Male karyotype- sex chromosomes are a big
   chromosome (X) and a small chromosome (y)
4. Female karyotype- sex chromosomes are two big
   chromosomes (XX)

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What are some types of genetic disorders

• 1. Autosomal Dominant- if dominant gene is
  present, person will have disorder
• Huntingtons disease
• Achondroplasia

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HUNTINGTONS DISEASE

• Caused by dominant allele
• Develops after age 30
• Lose muscle control, mental deterioration,
  eventually death.
• No cure

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Achondroplasia

• Dwarfism
• Defect in gene that controls cartilage formation
• Shortened stature
• Some have normal sized torso but shortened limbs.

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What are some types of genetic disorders?

• 2. Autosomal Recessive- must have two recessive
  genes to show disorder
• Phenylketonuria
• Cystic Fibrosis
• Tay-Sachs
• Sickle cell anemia

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PHENYLKETONURIA

• Also called PKU
• Must inherit two recessive alleles to show this
  disease.
• Unable to synthesize the enzyme that breaks down
  the amino acid phenylalanine. Phenylalanine
  accumulates and kills brain cells.
• Tested at birth- if present, put on diet low in
  phenylalanine (no milk) for first six years to
  prevent brain damage.

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CYSTIC FIBROSIS

• Also called CF
• Caused by a recessive allele
• on chromosome 7.
• Serious digestive problems, thick mucus that
  clogs lungs. Makes breathing digesting food
  very difficult.

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TAY-SACHS DISEASE

• Caused by two recessive alleles
• Occurs mostly in Jewish families
• Fats accumulate in brain cells, mental
  deficiency, delayed development, blindness
• Usually results in death within first few years
  of life.

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SICKLE-CELL ANEMIA

• Red blood cells are half moon shaped instead of
  round.
• Clog blood vessels, depriving tissues of oxygen-
  causes severe pain, weakness.
• Found more often in people of African descent.

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What are some types of genetic disorders?

• 3. Sex-Linked- disorder on sex chromosomes
• Klinefelters syndrome
• Turners syndrome
• XYY males

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KLINEFELTERS SYNDROME

• Males with an extra X chromosome
• XXY
• Sterile
• Some degree of mental deficiency

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TURNERS SYNDROME

• Females with only one X chromosome.
• XO
• Sterile
• Short, with thick, webbed necks, mild mental
  deficiency.

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XYY MALES

• Males with extra Y chromosome
• taller than average
• Produce more testosterone, some say more
  aggressive