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Chromosomes and Human Heredity

This chapter delves into the world of chromosomes and human heredity, focusing on karyotype studies, nondisjunction events, and chromosomal disorders like Down Syndrome. A karyotype, obtained by arranging homologous chromosomes by size, helps identify chromosomal abnormalities. Nondisjunction, the failure of sister chromatids to separate, can lead to conditions such as trisomy and monosomy. Down Syndrome, characterized by an extra chromosome 21, occurs in 1 in 800 births and shows increased prevalence with maternal age. Fetal testing for genetic disorders is also discussed.

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Chromosomes and Human Heredity

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  1. Chromosomes and Human Heredity Chapter 11.3 Pg. 311

  2. Karyotype Studies • Pairs of homologous chromosomes are arranged in decreasing size to produce a micrograph called a karyotype • Scientists have found that chromosomes end in protective caps called telomeres • Telomere caps consist of DNA associated with proteins

  3. Telomeres also might be involved in both aging and cancer

  4. Nondisjunction • Cell division during which sister chromatids fail to separate properly, which does happen occasionally, is called nondisjunction • Nondisjunction can result in extra copies of a certain chromosome or only one copy of a particular chromosome • Set of 3 chromosomes of one kind is called Trisomy

  5. Only one of a particular type of chromosome is called monosomy • Alterations of chromosome number are associated with serious human disorders, which are often fatal

  6. Down Syndrome • one of the earliest known human chromosomal disorders • Result of an extra chromosome 21(trisomy 21) • Distinctive facial features, short stature, heart defects, and mental disabilities

  7. Frequency in the US: 1/800 children are born with Down Syndrome • Frequency also increases with increasing age of mother • 6% increase in chance with mothers who are 45+ www.downsyndrome.com www.downsyndrome.com

  8. Fetal Testing • Couples who suspect they might be carriers for certain genetic disorders might want to have a fetal test performed • Test can only be performed if both mother and unborn child are in good health

  9. Movie Clip! http://player.discoveryeducation.com/index.cfm?guidAssetId=AB274EB9-EDF1-40F0-9122-5B996E8E08E0&blnFromSearch=1&productcode=US

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