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Chapter12 - Defective allele is dominant Pedigree Genetic...

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2/5/11 1 Chapter 12 Chromosomes and Inheritance Linkage Genes that are on the same chromosome do not independently assort Example: X chromosome (female) and certain disorders Color-blindness Seen more often in males The genes for seeing red and green color are on the X chromosome Males have only one X, therefore only one chance to get functional genes Definition of autosomes Autosomes are the 22 pairs of chromosomes that are not X & Y (X & Y are the sex chromosomes) Inheritance types X-linked Almost all known traits are recessive Autosomal Recessive or dominant
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2/5/11 2 Sickle-cell anemia Hemoglobin protein in red blood cells has defective structure (recessive gene) Under various stresses, hemoglobin precipitates and deforms red blood cell Blocks blood flow in capillaries, causing pain and tissue damage Huntington disease Nervous system deterioration, ultimately fatal Onset typically in middle age
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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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Chapter12 - Defective allele is dominant Pedigree Genetic...

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