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Unformatted text preview: Defective allele is dominant Pedigree Genetic information in family tree Females: circles Males: squares Color in those affected Show parents & siblings with lines Make deductions about genotypes 2/5/11 3 Polyploidy Extra sets of chromosomes Common in plants Fatal to humans Nondisjunction Error in meiosis Homologous chromosomes fail to separate Leads to polyploidy, or aneuploidy (extra or missing chromosome) Humans can have extra 13, 18, 21 or X: other extras lead to miscarriage Down syndrome Trisomy 21 Characteristic facial features Heart defects, mental retardation 1/700 births Incidence rises with mother’s age Nondisjunction of sex chromosomes Turner syndrome, X0 Female, short stature, sterile Klinefelter syndrome, XXY Male, testosterone deficient, sterile Aneuploidy in mitosis may be related to cancer...
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- Fall '08
- Biology, sex chromosomes, Turner syndrome, age Defective allele, chromosomes Common