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The Human Karyotype & Nondisjunction

Delve into the human karyotype, exploring chromosomal abnormalities like Nondisjunction and its associated genetic disorders like Down Syndrome, Turner Syndrome, and Klinefelter Syndrome.

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The Human Karyotype & Nondisjunction

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  1. The Human Karyotype & Nondisjunction

  2. What’s a Karyotype?? • Scientists use a microscope to take pictures of the condensed chromosomes during metaphase. • They can match up the homologous chromosomes by size and shape. • This arrangement of chromosomes is called a KARYOTYPE.

  3. A closer look at a karyotype… The human karyotype has 23 pairs or 46 chromosomes Sex chromosomes

  4. Remember, Meiosis results in the formation of FOUR daughter cells from ONEparent cell. • Meiosis results in the formation of GAMETES (either eggs or sperm) which are then combined together to form a new individual.

  5. The gametes come together… Egg (N), haploid Sperm (N), haploid Embryo (2N), diploid

  6. Uh Oh! Problems with Meiosis… • Usually Meiosis occurs with NO PROBLEMS. BUT, sometimes sex cells (gametes) are formed with irregular chromosomes numbers!! • Nondisjunction: Homologous chromosomes DO NOT SEPARATE during meiosis. Gametes are produced with the WRONG NUMBER of chromosomes!!

  7. Nondisjunction

  8. Down Syndrome • Results from having 47 chromosomes instead of 46 • People with Downs Syndrome have 3 copies of chromosome 21 • Have similar facial features, mental and physical disabilities

  9. Turner Syndrome • Female born with only 1 “X” chromosome (instead of 2) • Do not develop into puberty (therefore, they can’t reproduce) • Sometimes females have 3 “X’s”… these women CAN reproduce but are often taller and thinner than women with “normal” chromosome number

  10. Klinefelter Syndrome • Males born with 2 “X” chromosomes and 1 “Y” • Produce less testosterone (Sex hormone) and can’t father children

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