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Genetic Changes

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Genetic Changes Any mistake or change in the DNA sequence is called a mutation. Types of mutations are: point mutation frameshift mutation chromosomal mutation – PowerPoint PPT presentation

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Title: Genetic Changes


1
Genetic Changes
  • Any mistake or change in the DNA sequence is
    called a mutation.
  • Types of mutations are
  • point mutation
  • frameshift mutation
  • chromosomal mutation

2
Point Mutation
  • A change in a single base in DNA.

3
Frameshift Mutations
  • A single base is added or deleted from DNA.
  • Usually change the amino acid sequence
  • results in a protein that may not function
    properly

4
Chromosomal Mutations
  • Changes the number or structure of chromosomes
  • Few are passed on to the next generation, because
    the zygote usually dies.

5
4 Types of Chromosomal Mutations
  • Deletions loss of all or part of a chromosome
  • Insertions/Duplication part of a chromatid
    breaks off and attaches to its sister chromatid
    causing a duplication of genes on the same
    chromosome
  • Inversions part of a chromosome breaks off and
    is reinserted backwards (inverted)
  • Translocations part of one chromosome breaks
    off and reattaches to a different chromosome

6
Nondisjunction
  • The failure of homologous chromosomes to separate
    properly during meiosis
  • Both chromosomes of a homologous pair move to the
    same pole of the cell.
  • One cell will have an extra chromosome, and the
    other will be missing a chromosome.
  • Organisms with extra chromosomes often survive
    organisms lacking one or more chromosomes do not.

7
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8
Causes of Mutations
  • Any thing that causes a mutation is called a
    mutagen.
  • Mutations are generally random events and provide
    variations that enables species to evolve.
  • Many environmental agents also cause mutations.
  • Exposure to X-rays, UV light, radioactive
    substances, or certain chemicals can cause
    changes to DNA.

9
Karyotypes
  • A picture taken of stained chromosomes found in a
    cell during metaphase.
  • Chromosomal disorders can be identified using a
    karyotype.
  • The picture is enlarged so the geneticist can cut
    apart and arrange the chromosome pairs by length,
    banding pattern, and centromere placement.
  • The geneticist can use the karyotype to see if
    there are too many chromosomes, too few
    chromosomes, or chromosomal abnormalities.

10
Normal Male Karyotype
Trisomy 21, Male Karyotype
11
Genetic Disorders
  • Hemophilia - Caused by a recessive gene on the X
    chromosome. One can bleed to death with small
    cuts.
  • Downs Syndrome - Caused by non-disjunction of the
    21st chromosome. 3 2lst chromosomes
  • Sickle Cell Anemia - red blood cells, normally
    disc-shaped, become crescent shaped, and get
    stuck in blood vessels
  • Cystic Fibrosis Recessive disorder, deletion of
    only 3 bases on chromosome 7, Fluid in lungs,
    potential respiratory failure
  • Tay-Sachs Disorder - autosomal recessive, Central
    nervous system degrades, ultimately causing
    death.
  • Color Blindness - x-linked recessive, cant
    distinguish between red and green

12
Downs Syndromeor Trisomy 21
13
Pedigrees
  • A diagram, similar to a family tree, used by
    geneticists to show genetic relationships within
    a family.
  • Pedigrees can
  • Show if a trait is inherited.
  • Show how a trait is passed from one generation to
    the next.
  • Determine whether an allele for a trait is
    dominant or recessive.

14
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15
Gel Electrophoresis
  • DNA Fingerprinting
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