Mutations and other genetic issues

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Mutations and other genetic issues

• Genetics Unit

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Mutations

• Changes in the genetic material.
• Any deviation from the normal chromosomal
  compliment
• Two types
• Spontaneous mutations-occur randomly no cause
  can be determined
• Induced mutations are caused by some traceable
  artificial factor exposure to chemicals,
  alcohol, drugs, radiation

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Mutations

• Mutations that produce changes in a single gene
  are gene mutations.
• Mutations that produce changes in a whole
  chromosome are chromosomal mutations.

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Gene Mutations

• Point mutation-change in one or just a few
  nucleotides. So named because it occurs at a
  single point.
• Substitutions
• Deletions
• Insertions

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Gene Mutations

• Frameshift mutationshift the reading frame of
  the genetic code
• Can alter a protein so much that it cant perform
  its job.

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Chromosomal Mutations

• Involve a change in the number or structure of
  the chromosome
• Some change the location of some genes on the
  chromosome
• Some may change the number of copies of some
  genes.

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Chromosomal Mutations

• Four main types of mutations
• Deletion
• Duplication
• Inversion
• translocation

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Deletion

• The permanent loss of a segment of chromosome
• Can be found anywhere on the chromosome
• Can be caused by heat, radiation, viruses,
  chemicals, errors

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Deletion
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Duplication

• Doubles a segment of chromosome
• Can be fatal
• Can be caused by uneven crossing over during
  meiosis or replication error before meiosis

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Duplication
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Causes of abnormalities

• Nondisjunction
• The failure of the chromosome pairs to separate
  during Meiosis I or Meiosis II
• Result will be a zygote with too many or too few
  chromosomes
• Two types Primary and secondary nondisjunction

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Primary Nondisjunction
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Secondary Nondisjunction
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Types of Genetics Tests

• When trying to determine a genetic problem, we
  can use non-invasive tests such as
• Pedigrees
• Karyotypes

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Pedigrees

• A pedigree follows a specific trait through
  several generations
• Resembling a type of map, the pedigree uses
  symbols to represent certain elements

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Pedigree key
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Pedigree
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Karyotypes

• A photographic inventory of an individuals
  chromosomes
• Can show the individuals gender and any
  abnormalities in chromosome number or structure

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Karyotypes
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Karyotypes
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Amniocentesis

• An invasive test that obtains amniotic fluid
  surrounding the fetus using a needle

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Amniocentesis Pros and Cons

• Able to determine fetus gender and/or any
  abnormalities
• Cant be done before 16th week of pregnancy
• Can cause infection to mother and/or fetus
• Can cause premature delivery and birth

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Chorionic Villus Sampling (CVS)
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CVS Pros and Cons

• Can determine fetus gender and any genetic
  abnormalities
• Can be done after 10 weeks
• Can cause leakage of amniotic fluid
• Can cause premature labor and delivery

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Recessive Disorders

• Must be inherited from BOTH parents
• Autosomal recessive disorders (non-sex cells)
• Tay-Sachs
• PKU
• Cystic fibrosis

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Recessive Disorders

• Tay-Sachslipid accumulation in the brain mental
  deficiency blindness, death in early childhood
• PKU-phenylketonuriaaccumulation of phenylalanine
  in tissues lack of normal skin pigment mental
  retardation
• Cystic fibrosisexcess mucus in lungs, digestive
  tract, liver increased susceptibility to
  infections often die young

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Dominant Disorders

• Can get the disorder by inheriting only one
  dominant allele
• Huntingtons disease
• Achondroplasia

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Dominant Disorders

• Huntingtons Disease
• Mental deterioration and uncontrollable movements
• Doesnt appear until middle age
• Achondroplasia
• One form of dwarfism

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Sex Linked Disorders

• Is there a pattern of inheritance for genes
  located on the X or Y chromosome? YES especially
  on the X
• Many times it is male children that inherit these
  disorders from their mothers because . . . They
  inherit their X from their moms
• Many sex linked genes are on the X
• Colorblindness
• Hemophilia
• Duchenne Muscular Dystrophy

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Sex Linked Disorders

• Colorblindness
• Most often found in males
• 1 in 10 males
• Females have to inherit from both parents
• 1 in 100 females
• Most common is red-green colorblindness

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Sex Linked Disorders

• Hemophilia
• Two genes on the X chromosome control blood
  clotting
• Many times it is male children that inherit this
  from their moms X chromosome
• 1 in 10,000 males
• A bleeding disorder can cause death in severe
  cases

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Sex Linked Disorders

• Duchenne Muscular Dystrophy
• 1 in 3000 males
• Progressive weakening and loss of skeletal muscle
• Caused by defective version of gene that codes
  for a muscle protein

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Genetic Disorders

• Trisomy
• Downs Syndrome (extra chromosome 21)
• Edwards Syndrome (extra chromosome 18)
• Patau Syndrome(extra chromosome 13)

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Downs Syndrome (Trisomy 21)
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Edwards Syndrome (Trisomy 18)
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Patau Syndrome (Trisomy 13)
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Turners Syndrome
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Turners Karyotype
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Klinefelters Syndrome