Human Genetics

I. Mutations = changes in DNA A. Mutations increase the amount of variation among offspring. A.Deletion: removal of a chromosomal segment B.Duplication: repeats a chromosomal segment C.Inversion: segment reversal in a chromosome D.Translocation: movement of a chromosomal segment to another non-homologous chromosome II. Chromosome Mutations

III. Karyotypes A.Shows chromosomes paired by size, shape, and appearance in metaphase. B.Chorionic villi sampling, and amniocentesis can be used to diagnose chromosomal abnormalities.

IV. Changing Chromosome Number A.Nondisjunction = failure of chromosomes to separate during meiosis; addition or loss of a chromosome B. Monosomy missing 1 chromosome (45) C. Trisomy have an extra chromosome (47)

V. Nondisjunction Abnormalities A. Many trisomies and nearly all monosomies are fatal. B. XYY males (Jacob syndrome)- tall, acne, not overly aggressive C. XO females (Turner syndrome)- short, webbed neck, no puberty.

D. Klinefelter Syndrome = XXY; male, some retardation, low fertility (rare cases (48,XXXY) or (49,XXXXY) E. Triple X Female (XXX) – no physical abnormalities F. Fragile X Syndrome – X chromosome broken; males; hyperactive or autistic, delayed speech G. Down Syndrome = extra 21st chromosome; mental retardation, fold of skin above eyes, weak muscles

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VI. Sex Determination A. A.Thomas Hunt Morgan 1. Experiments with Drosophila (fruit fly) 2. Sex Chromosomes Determine Gender a. Female are XX b. Male are XY

D. Sex chromosomes also carry genes for traits unrelated to gender. E. Recessive alleles on X expressed in males more often. F. Carrier: Someone who is heterozygous for a genetic disease or trait. is heterozygous for a genetic disease or trait.

G. Example of Sex Link Traits 1. Color Blindness 2. Hemophilia – blood doesn’t clot x x = Healthyx y = Healthy x x = Healthy x y = hemophilia X X = hemophilia X X = hemophilia Hh H H h h

VII. Human Genetic Traits A. Single Allele Traits 1. Sickle Cell Anemia a. Sickle shaped red cells b. Clump & block arteries c. AA= healthy cell AA’= both kinds; protected from malaria A’A’= sickle cells B. Other examples 1. Tays-Sacs 2. Cystic Fibrosis 3. Phenylketonuria (PKU)

C. Dominant Allele Diseases 1. Huntington’s Disease a. Brain cells degenerate; no muscle control; death b. Occurs at 30 – 40 years oldHhhhHhhh H h hhhh

D. Polygenic Traits are traits that have 2 or more genes controlling it. 1.Skin color genes with additive effect of amount of melanin 2. Eye Color – blue (light melanin), brown (lot of melanin) 3. Height

E. Sex Influenced Traits are influenced by sex hormones 1. B = Baldness; dominant in males and recessive in females 2. BB = bald females and males 3. BB” – female will not lose her hair 4. BB” – male will lose hair

End notes Today

VIII. Studying Humans A. Population Sampling = select a number to represent whole population B. Twin Studies – environment vs. genetics C. Pedigree Studies – family chart of traits

D. DNA fingerprinting = study the patterns of bands obtained from electrophoresis 1. Gel electrophoresis – process to separate DNA fragments by size of charge

E. Pedigrees are charts or “family trees” that track which members of a family have a particular trait.

IF THEY IF THEY MATED… MATED…

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