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Genetics

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Genetics

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  1. Genetics

  2. Genetics • the study of heredity • the way in which traits of parents are passed on to offspring

  3. Father of Genetics • Gregor Mendel • Austrian monk • did experiments with peas and proved that certain characteristics……..

  4. ………. • Such as color and height, are passed from parent to offspring

  5. Differences • all differences in organisms are not caused by genetics • some are caused by the environment • the conditions under which the animals are raised

  6. Parts of the cell • cell membrane - contains the cytoplasm and the nucleus

  7. Cytoplasm • protects and cushions the nucleus

  8. Nucleus • contains the genetic material

  9. Chromosomes • carry the genes • exist in pairs in all cells except sperm and egg cells

  10. Genes • single determiner of a hereditary trait

  11. Cell Division • two types • Mitosis • Meiosis

  12. Mitosis • cell division for growth • this division never ends • chromosome pairs are duplicated exactly alike

  13. Mitosis • each new cell is exactly like the old ones • asexual division • chromosomes are in pairs

  14. Mitosis • steps of mitosis • Prophase (Interphase) • Metaphase • Anaphase

  15. Steps • Telophase • Cytokinesis • ** PMATC

  16. Meiosis • cell division of reproductive cells (sperm and egg) • each new cell is not exactly like the old one

  17. Meiosis • in each new cell chromosomes are not in pairs • each new cell contains half of the original number of chromosomes

  18. Meiosis • allows for random assortment of parental genes

  19. Gamete • mature egg or sperm cell • each gamete has half the original number of chromosomes

  20. Dominant gene • in a pair, hides the effect of another gene

  21. Recessive gene • the gene which is hidden by a dominant gene

  22. Examples • of dominant genes • tongue rolling • free ear lobes • polled cattle

  23. Examples • of recessive genes • color red in Holsteins • dwarfism

  24. Symbols • dominant genes • capital letters A

  25. Symbols • recessive genes • lower case letters a

  26. Homozygous • gene pairs • one which carries two genes for a trait • both represented by capital or lower case letters

  27. Homozygous • polled - PP • horned - pp

  28. Heterozygous • gene pairs • one which carries one dominant and one recessive gene

  29. Heterozygous • Pp

  30. Genotype • genetic makeup of an animal or a given trait expressed by symbols • Ex: PP, AA, Pp, Aa, aa

  31. Phenotype • physical appearance expressed in words • Ex: polled, horned

  32. Mitosis T t Meiosis T t Mitosis t t

  33. Steps of Meiosis • Prophase I ( Interphase) • Metaphase I • Anaphase I • Telophase I

  34. Steps of Meiosis • Prophase II (Interphase) • Metaphase II • Anaphase II • Telophase II • Cytokinesis

  35. If • two heterozygous animals are mated • the number of traits being selected is six • the total number of offspring is over 16,000,000

  36. Incomplete Dominance • when one gene does not hide the effect of the other in a gene pair • result is a mixture of the two traits

  37. Incomplete Dominance • Roan coloring in cattle • RR X WW = RW • Red X White = Roan • Roan - mixture of red and white hairs

  38. Sex determination • male sex chromosomes • male mammals have two different sex chromosomes • XY • females are XX

  39. Sex determination • poultry • the female determines the sex of the offspring • female is ZW • male is ZZ

  40. Sex Linked Traits • genes which are carried only on the sex chromosomes • ex: red green color blindness • 2:25 males • 1:150 females

  41. Sex Linked Traits • hemophilia • bleeders’ disease • more common in males than in females

  42. Sex Linked Traits • barred feather pattern vs black in chickens

  43. Mutation • when a new trait is shown that did not exist in either parent

  44. Mutation • the new breed of polled Herefords • which resulted from the crossing of two horned animals

  45. Causes of Mutations • radiation (nuclear accident or x-ray) • chemicals

  46. Systems of breeding • purebreeding • inbreeding • outcrossing • grading up • crossbreeding

  47. Purebreeding • purebred is defined as a member of a breed • the animals of which possess a common ancestry • distinctive characteristics

  48. Purebreeding • is registered or eligible for registry

  49. Outcrossing • mating of animals of different families within the same breed • relatively safe system of breeding

  50. Outcrossing • unlikely that two unrelated animals would carry the same undesirable genes and pass them on