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Human Genetics

Human Genetics. Human Genetics. I. Mutations= changes in DNA. A. 2 Types 1. Chromosome – occurs during mitosis and meiosis. a. Deletion – piece of chromosome breaks off b. Inversion – piece breaks off and reattaches in reverse order.

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Human Genetics

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  1. Human Genetics Human Genetics

  2. I. Mutations= changes in DNA A. 2 Types 1. Chromosome – occurs during mitosis and meiosis

  3. a.Deletion – piece of chromosome breaks off b.Inversion – piece breaks off and reattaches in reverse order

  4. c.Translocation – Broken piece attaches to nonhomologous chromosome d. Insertion (Addition or Duplication)– piece of DNA is inserted into a chromosome

  5. 2. Gene Mutation a. Point Mutation= add, substitute or delete a base b. Frame Shift Mutation= base code is read out of sequence

  6. B. Causes of Mutations • Chance • Mutagen = environmental factor damages DNA Ex. UV light (sun; skin cancer), cigarette tar, asbestos, virus, radiation

  7. Human Genetics • A. Single Allele Traits 1. Sickle Cell Anemia a. Sickle shaped red cells b. Clump; block arteries, lack 02, pain, weakness, death c. AA= normal cell AA’= both kinds; protected from malaria A’A’= sickle cells

  8. 2. Huntington’s Disease • Cause by one dominant allele a. Brain cells degenerate; no muscle control; death b. Occurs at 30 -40; passed to child 50% of time H h h h

  9. 3 3. Tays-Sacs, Cystic Fibrosis, Phenylketonuria Tays Sachs Disease is an inherited incurable disease of the central nervous system. Its symptoms first appear when a baby is about 6 months old. The baby stops smiling and developing through the normal developmental stages. Blindness and paralysis follow within the next four years resulting in the child's death by the age of five years. Most babies die within the first two years.

  10. B. Polygenic Traits • = 2 or more genes control trait 1.Skin color - 4-7 genes with additive effect of amount of melanin 2. Eye Color – blue (light melanin), brown (lot of melanin) 3. Height

  11. Albino Dolphin

  12. C. Multiple Allele Traits • = Trait with 3 or more alleles; only get 2 1. ABO Blood group system; types – A, B, AB, O 2. AA =type A AO = type A OO = type O BB= type B BO = type B AB= type AB • *A,B codominant *Both dominant to O

  13. D. Sex Linked Traits • = Trait controlled by gene on sex chromosome 1. XX = female XY = male 2. Y = Blank, only minimal expression of traits 3. Single, recessive allele on X expressed 4. Males express sex-linked alleles more

  14. 5. Example of Sex Link Traits • Color Blindness • Hemophilia – blood doesn’t clot x x = normal x y = normal x x = normal x y = hemopheliac H h H H H h

  15. Sex Influenced Traits = not a sex chromosomes; 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 BB” – male will lose hair

  16. Nondisjunction = addition or loss of a chromosome; chromatids do not separate during meiosis 1. Monosomy = less one chromosomes (45) A. Turner Syndrome – XO sterile, immature female. Turner syndrome affects approximately 1 out of every 2,500 female live births worldwide. It embraces a broad spectrum of features, from major heart defects to minor cosmetic issues. Some individuals with Turner syndrome may have only a few features, while others may have many. Almost all people with Turner syndrome have short stature and loss of ovarian function, but the severity of these problems varies considerably amongst individuals.

  17. Trisomy = Extra chromosomes (47) • A. Klinefelter Syndrome = XXY; male, some retardation, low fertility • (rare cases three (48,XXXY) or four (49,XXXXY) • B. Down Syndrome = extra 21st chromosome; mental retardation, fold of skin above eyes, weak muscles

  18. III. 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

  19. Twins

  20. D. DNA fingerprinting = study the • patterns of bands obtained • from electrophoresis • 1. Gel electrophoresis – process to • separate DNA fragments • by size of charge • 2. Restirction enzymes-recognize sequences; cut DNA into fragments

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