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Human Heredity

Human Heredity. A look at Several Genetic Disorders. Human Chromosomes. Humans have 46 chromosomes- 23 pairs 23 from mom’s egg + 23 from dad’s sperm Autosomes are the first 22 pairs Sex Chromosomes are the last pair Genotype of Female is XX Genotype of Male is XY.

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Human Heredity

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  1. Human Heredity A look at Several Genetic Disorders

  2. Human Chromosomes • Humans have 46 chromosomes- 23 pairs • 23 from mom’s egg + 23 from dad’s sperm • Autosomes are the first 22 pairs • Sex Chromosomes are the last pair • Genotype of Female is XX • Genotype of Male is XY

  3. Karyotype: picture of chromosomes

  4. Most genetic disorders are caused by RECESSIVE alleles. • Cystic fibrosis- large accumulation of muscus due to lack of protein. • Phenylketonuria (PKU)- lack enzyme that converts phenylalanine to tyrosine. • Tay-Sachs- lack of enzyme that breaks down fat in the CNS • Albinism- lack of pigment in skin.

  5. Cystic Fibrosis • Caused by a defect in a protein that results in an overproduction of muscus. • Favors bacterial infections. • 1 in 20 white Americans are carriers. • 1 in every 2000 children born to white americans has this disorder. • Without treatments, most children die before age 5. • With treatments, can live into 20’s+

  6. Tay-Sachs • Lack enzyme that breaks down fat in the CNS- fat collects on the brain. • No treatment or cure. Most will die before the age of 6. • http://www.pbs.org/wgbh/nova/genome/media/2809_q056_03.html

  7. Albinism

  8. Disorders caused by dominant alleles: • Huntington’s Disease: neurodegenerativegenetic disorder that affects muscle coordination and leads to cognitive decline and psychiatric problems,typically becomes noticeable in mid-adult life. • Dwarfism: adult height of less than 4 feet 10 inches • Polydactylism

  9. Huntington’s Disease http://www.youtube.com/watch?v=u9XzqreToII&feature=related

  10. Dwarfism • http://www.youtube.com/watch?v=iC5B3zU0Iv0

  11. Polydactyl- more than 5 digits on hand or foot

  12. Caused by changes in DNA (mutations): • Sickle-cell Anemia: amino acid is changed in hemoglobin to give cells a sickle shape. Blocks the flow of red blood cells.

  13. Sickle Cell Anemia • http://www.youtube.com/watch?v=ujf72mjy0Bg

  14. Some genetic disorders are Sex-Linked • Most commonly found in males • Mostly on X chromosome (recessive) and since males have only one X chromosome they will express the disorder more often. • Examples: • Colorblindness • Hemophilia: blood cannot clot • Muscular Dystrophy: affects muscle development

  15. Colorblindness (write what is red) • Some genes are located on the X chromosome. Females receive two alleles for these genes, but males only receive one. • If the parent is a male, the genotype is automatically known. A colorblind male has to be b, since he only has one allele and colorblindness is recessive. A normal male must then be B • Females can be heterozygous for the colorblindness trait - they are called carriers. A female can be BB - normal, Bb - carrier, or bb - colorblind

  16. The following shows a cross between a normal man and a woman who is a carrier (COPY THIS)

  17. colorblindess test

  18. Hemophilia • http://www.youtube.com/watch?v=FS64UXi74lY

  19. Chromosomal Disorders • Nondisjunction: chromosomes fail to separate properly during meiosis (formation of gametes) • Down Syndrome- extra chromosome on #21 (results in total of 47 chrom) • Turner’s • Klinefelter’s

  20. Down Syndrome- Extra chromosome on #21. Total of 47 chromosomes

  21. Down Syndrome Karyotype

  22. Klinefelter’sKaryotype - XXY

  23. Klinefelter’s • XXY…….Only affects Males • Lower Muscle mass • Lower testosterone • Less Muscle, less facial hair, broader hips • Often Taller • Increase in Breast Tissue • Low Fertility

  24. Turner’s Karyotype – Missing one Sex Chromosome

  25. Turner’s Syndrome • X………Only affects Females • Shorter in Stature • Broader Chest • Lower Hairline • Webbed Neck • No Menstrual Cycle • Sterile

  26. Pedigree: graphic representation of genetic inheritance.- Male = square- Female = circle- Shaded = has the disorder or trait- Half shaded = carrier of disorder or trait (heterozygous)- Unshaded = neither affected nor a carrier

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