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HUMAN GENETIC TRAITS AND DISORDERS – Notes 14.2

HUMAN GENETIC TRAITS AND DISORDERS – Notes 14.2. SINGLE ALLELE - DOMINANT. Meaning if you have the homozygous dominant or heterozygous genotype, then you have the trait or disorder (Example: DD or Dd). Rh BLOOD TYPE.

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HUMAN GENETIC TRAITS AND DISORDERS – Notes 14.2

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  1. HUMAN GENETIC TRAITS AND DISORDERS – Notes 14.2

  2. SINGLE ALLELE - DOMINANT Meaning if you have the homozygous dominant or heterozygous genotype, then you have the trait or disorder (Example: DD or Dd)

  3. Rh BLOOD TYPE • People have RH+ factor antigen (marker) on the surface of their red blood cells • Rh + = DD or Dd • Rh - = dd • Named for rhesus monkeys • Can lead to complications between mother and fetus

  4. ACHONDROPLASIA • Average size trunk and shorter limbs due to disturbance of bone-producing cells in the growth plates of bones • Achondroplasia = DD or Dd • No achondroplasia = dd • Can also be caused by a gene mutation

  5. CATARACTS • Acondition in which the lens of the eye becomes opaque (cloudy) • Cataracts = DD or Dd • No cataracts = dd

  6. POLYDACTYLY • Extra fingers or toes • Polydactyl = DD or Dd • No polydactyl = dd

  7. HUNTINGTON’S DISEASE (HD) • Gradual deterioration of brain tissue in middle age; shortened life expectancy (found on chromosome 4) • HD = DD or Dd • No Hd = dd

  8. SINGLE ALLELE - RECESSIVE Meaning if you have the homozygous recessive genotype, then you have the trait or disorder (Example: nn)

  9. ALBINISM • Unable to produce melanin, the pigment responsible for skin, hair, and eye color • Albinism = nn • No Albinism = NN or Nn

  10. CYSTIC FIBROSIS • Mucus clogs lungs, liver, and pancreas; victims usually don’t survive to adulthood. Caused by a defective cell membrane protein • Cystic Fibrosis = nn • No Cystic Fibrosis = NN or Nn

  11. PHENYLKETONURIA (PKU) • Failure of brain to develop in infancy due to defective enzyme for phenylananine metabolism. Can be treated by diet. If not treated, can cause death. Tested for at birth • PKU = nn • No PKU = NN or Nn

  12. TAY-SACHS DISEASE • Deterioration of central nervous system in infancy; death occurs in early childhood. Due to a defective enzyme. • Tay-sachs = nn • No Tay-sachs = NN or Nn

  13. HEREDITARY DEAFNESS • Cannot hear • Deaf = nn • Not deaf = NN or Nn

  14. SICKLE CELL ANEMIA • Impaired blood circulation and organ damage due to abnormal crescent shaped red blood cells from abnormal hemoglobin protein molecules • Sickle Cell = ss • No Sickle cell = SS or Ss

  15. X-LINKED TRAITS occur because the allele for these traits appears only on the X chromosome (can also be called Sex-linked traits)

  16. COLORBLINDNESS • Inability to distinguish colors from each other (usually red and green) • Colorblind Female = XnXn or XcXc • Colorblind Male = XnY or XcY

  17. HEMOPHILIA • Failure of blood to clot because defective blood-clotting factor • Hemophiliac female = XnXn or XhXh • Hemophiliac male = XnY or XhY

  18. MUSCULAR DYSTROPHY • Wasting away of muscles; shortened life expectancy due to degeneration of muscle fibers caused by a defective protein • M.D. Female = XnXn • M.D. Male = XnY

  19. ICHTHYOSIS SIMPLEX • (fish-skin disease) – dryness and scaliness of the skin due to skin cells that do not slough off properly • IS Female = XnXn • IS Male = XnY

  20. SEX-INFLUENCED TRAITS occur due to the presence of male or female hormones that influence the expression of the trait

  21. PATTERN BALDNESS • Causes loss of hair • Bald Female = bb • Bald Male = BB or Bb

  22. Nondisjunction NONDISJUNCTION occurs when a replicated chromosome pair doesn’t separate during anaphase of meiosis The centromere does not split This changes the chromosome NUMBER

  23. Nondisjunction • This causes: • MONOSOMY the zygote has only one chromosome of a homologous pair (45 total chromosomes) • TRISOMY the zygote has three homologous chromosomes instead of two in a homologous pair (47 total chromosomes)

  24. Examples of Nondisjunction • DOWN SYNDROME (caused by trisomy 21) • Mental retardation • Short hands, feet, and trunk • Fold of skin above eyes • Heart defects • Muscle weakness • Respiratory ailments

  25. Examples of Nondisjunction • TURNER SYNDROME (caused by monosomy X) • Female • Short stature and broad chest • Webbed neck • Underdeveloped female organs

  26. Examples of Nondisjunction • KLEINFELTER SYNDROME (caused by trisomy XXY) • Male • Sparse body hair and low/no fertility • May have breast development • Unusually long-legged • May have mental retardation

  27. Examples of Nondisjunction • EDWARDS’ SYNDROME (caused by trisomy 18) • Severe mental retardation • Very characteristic malformations of the skull, pelvis, and feet • Usually die in early infancy

  28. Examples of Nondisjunction • PATAU SYNDROME (caused by trisomy 13) • Abnormal brain function that is very severe • Many facial malformations • Usually die in early infancy

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