Types of Cancer

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Types of Cancer

• Carcinomas originate in external or internal
  body coverings (e.g. skin or intestinal lining)
• Sarcomas originate in support tissue (e.g. bone
  or muscle)
• Leukemias bone marrow
• Lymphoma spleen and lymph nodes

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Chromosome arrangement

• Somatic cells typical body cells
• 46 chromosomes in 23 pairs (humans)
• Each pair is called homologous chromosomes
• Gametes sex cells
• 23 chromosomes

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Homologous chromosomes

• 22 of the pairs (autosomes) are true homologues
• One of each came from mom and dad
• Identical in length and type of genes carried
• Genes on each are slightly different
• Sex chromosomes (23rd pair) dont match up
  exactly (X vs Y)

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Meiosis

• Produces haploid cells
• Results in four daughter cells
• All are haploid
• All are genetically unique from each other and
  from the parent
• DNA replicated before meiosis begins
• Two stages
• Meiosis I separates homologous chromosomes
• Meiosis II separates sister chromatids

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Sexual Reproduction leads to genetic variation

• 3 process that contribute to variation
• Crossing over during prophase I
• Orientation of homologues during metaphase I
• Random fertilization

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Tetrads ? 4 gametes
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Crossing Over
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Karyotype
Centromere
Sister
chromatids
Pair of homologous
chromosomes
2,600?
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Alterations in Chromosome Number

• Nondisjunction when a pair of chromosomes fail
  to separate
• Meiosis I when homologs fail to separate
• Meiosis II when sister chromatids fail to
  separate
• Can happen in autosomes or sex chromosomes

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Alterations in Chromosome Number
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Alterations in Chromosome Number Autosomes
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Down Syndrome

• Nondisjunction in chromosome 21
• AKA trisomy 21
• Results in 47 chromosomes (instead of 46)
• Affects 1 in 700 births
• Incidence increases dramatically with age of
  mother

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Alterations in Chromosome Number Sex Chromosomes
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