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Genetics and Heredity Part II

Genetics and Heredity Part II. Is the study of genetics and heredity really as simple as 2 alleles and a Punnett square?. Unfortunately, NO. Darn . . . The following concepts make genetics more interesting and also more complicated:

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Genetics and Heredity Part II

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  1. Genetics and Heredity Part II

  2. Is the study of genetics and heredity really as simple as 2 alleles and a Punnett square?

  3. Unfortunately, NO. Darn . . .

  4. The following concepts make genetics more interesting and also more complicated: - incomplete dominance - multiple alleles - polygenic inheritance - environmental factors - chromosome disorders - sex-linked disorders

  5. Incomplete Dominance Incomplete dominance occurs when the offspring of 2 homozygous parents show an intermediate phenotype. (#6)

  6. + RED WHITE PINK (RR) (WW) (RW)

  7. Red and white are equally dominant colors first generation Second generation: red and white reappear

  8. curly + straight Type of Hair wavy

  9. Multiple Alleles Many traits are controlled by multiple alleles. They produce 3 or more phenotypes.

  10. Ex: blood types 3 alleles for blood A, B, O produce 4 blood types: A, AB, B, O

  11. Polygenic Inheritance Polygenic inheritance occurs when a group of genes work together to produce one trait. #9

  12. As a result, many phenotypes are produced. These 3 gene pairs work together to determine one trait.

  13. Ex: hair color, eye color, skin tone

  14. Environmental Factors Your environment may help determine which traits are expressed.

  15. Ex: Your diet, exposure to chemicals or sunlight, and temperature can affect genetics.

  16. Chromosome Disorders Every species has a specific # of chromosomes. Humans have 46 chromosomes or 23pairs.

  17. Human Chromosomes Pair #23 determines gender: XX = girl XY = boy.

  18. Sometimes an error occurs during meiosis and a gamete (egg or sperm) has too many or too few chromosomes. # of chromosomes ≠ 23

  19. A zygote formed with one of these defective gametes usually dies. If the zygote survives, the baby will be born with a disorder or disability.

  20. Examples of Chromosome Disorders Down’s Syndrome: 3 copies of chromosome #21; short stature, oversized heart, learning disabilities (#10)

  21. Turner syndrome: only affects girls; are missing part or all of one X chromosome; neck webbing, short, infertile, severe heart and kidney problems (#13)

  22. Autism:brain disorder; repetitive movements, delays in speech, learning, and socialization Marfan’s Syndrome: affects connective tissue; thin body, narrow face, long limbs (#13)

  23. This girl is missing part of her 18th chromosome. This boy is missing part of the 11thchromosome. (Jacobsen’s Syndrome) (#13)

  24. Sex-Linked Disorders Some conditions are passed only on the 23rd or the X or Y chromosome. Since these are our sexcells, the disorders are sex-linked.

  25. All eggs carry the X chromosome. The sperm determines the gender of a child. Females: XX Males: XY X X Y It’s a BOY!! It’s a GIRL!!

  26. If a disorder is carried on the X chromosome, both boys and girls can inherit it. (#12) Males:XY Females:XX If a disorder is carried on the Y chromosome, only boys can inherit it.

  27. Punnett square for a sex-linked disorder that’s carried on the X chromosome. Mother does not have the disorder, but carries and passes on the gene for it. Mother (carrier)

  28. Examples of Sex-Linked Disorders (#14) Baldness Colorblindness

  29. Duchenne Muscular Dystrophy (#14) Calico (cats’ fur)

  30. Hemophilia This hemophilia patient received only one injection (shot). The body reacted with severe bleeding under the skin. (bruising) (#14)

  31. Pedigrees A pedigree is a chart used to trace genetic traits throughout a family’s history.

  32. A pedigree is very useful when trying to find the pattern of inheritance of a genetic disorder. (colorblindness, baldness, hemophilia)

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