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Karyotypes and Nondisjunction

Karyotypes and Nondisjunction. KARYOTYPE: Definition. Picture of chromosomes taken during metaphase (mitosis) when chromosomes are fully condensed Chromosomes are arranged large to small by homologous pairs sex chromosomes shown last Normal human karyotypes show 46 chromosomes

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Karyotypes and Nondisjunction

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  1. Karyotypes and Nondisjunction

  2. KARYOTYPE: Definition • Picture of chromosomes taken during metaphase (mitosis) when chromosomes are fully condensed • Chromosomes are arranged large to small by homologous pairs • sex chromosomes shown last • Normal human karyotypes show 46 chromosomes • 44 autosomes (22 pairs of homologous chromosomes) • 2 sex chromosomes

  3. KARYOTYPE: Human Chromosomes

  4. KARYOTYPE: How it is useful • In order to study differences in size, shape, and chromosome number (too few or too many) • Determines the sex of the child • Usually done for humans when a known chromosomal disorder runs in family • (i.e. Down Syndrome) • Can be done for any organism

  5. NONDISJUNCTION:Definition and Results • Form of chromosomal mutation during meiosis when homologous chromosomes fail to separate • Results in abnormal number of chromosomes in gametes, which can possibly lead to a disorder in the offspring

  6. NONDISJUNCTION:Examples of Disorders • Down Syndrome – (autosome) - three copies of chromosome 21 • Karyotype shows 47 chromosomes (Trisomy 21) • Results in various degrees of mental disabilities, causes decrease immunities to diseases/organ defects, distinguished facial features • Edward’s Syndrome – (autosome) three copies of chromosome 18 • Karyotype shows 47 chromosomes (Trisomy 18) • Results in failure of all organ systems, death after a few months

  7. NONDISJUNCTION:Examples of Disorders • Turner’s Syndrome – (sex chromosome) – only one X chromosome is inherited • Karyotype 45, X • Results in sterile female, short in stature, heart and kidney defects • “Superfemale” – (sex chromosome) – extra X chromosome is inherited • Karyotype 47, XXX (Trisomy X) • Results in healthy, fertile female

  8. NONDISJUNCTION:Examples of Disorders • Klinefelter’s Syndrome – (sex chromosome) –extra X chromosome(s) is/are inherited • Karyotype 47, XXY (or even 48, XXXY; 49, XXXXY) • Usually results in sterile male • “Supermale” – (sex chromosome) – extra Y chromosome is inherited • Karyotype 47, XYY • Usually results in sterile, more violent, decreased intelligence, taller male

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