Chromosomes and Human Heredity

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

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

5. 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

6. 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

7. 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

8. 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

9. 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

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