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Genetics Unit

Genetics Unit. Introduction to Genetics. - Genetics is the study of heredity . - Heredity is how different genes are passed down from parents to children. PHENOTYPE.

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Genetics Unit

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  1. Genetics Unit

  2. Introduction to Genetics -Genetics is the study of heredity. -Heredity is how different genes are passed down from parents to children.

  3. PHENOTYPE • A phenotype is the expression of an observable physical trait or characteristic of an organism, such as stature or blood type, based on genetic and environmental influences.

  4. Examples vs Non-examples Hair PHENOTYPE Hair-do: not a phenotype Twins born with A weird girl who fros-out blonde and red hair her hair

  5. Phenotypes • Can you think of some examples of phenotypes? • Write down at least 2 examples of phenotypes (traits) in your notes

  6. How good are you at judging chimpanzee phenotype? Which chimps are related?

  7. Phenotypes? Yes or no? Polydactyl

  8. Phenotypes? Yes or no? • NO! • Flamingos get their pink color from the food they eat, not their genes!

  9. HOMOZYGOUS organism with two identical alleles for the same trait**root word “homo” = same

  10. HETEROZYGOUSorganism with twodifferentalleles for the same trait**root word “hetero” = different

  11. Homozygous vs. Heterozygous Two alleles for the “height gene” might be TALL (T) and SHORT (t) A homozygous individual would be TT or tt –two of the same alleles A heterozygous individual would be Tt –two DIFFERENT alleles

  12. DOMINANTallele that is expressed when at least one allele is present (TT or Tt = tall)“cover up”

  13. RECESSIVEallele that is expressed only when homozygous (no dominant allele)(tt = short)

  14. Dominant Recessive aa AA or Aa

  15. Dominant Recessive ww WW or Ww

  16. What could AC Slater’s genotype be? Zach’s? Dimples (D) No dimples (d) DD or Dd dd

  17. SNOWFLAKE –rare albino gorilla • Albinism • combination of recessive alleles passed from both parents of an individual • prevents the body from making the usual amounts of the pigment melanin • NN = Normal pigmentation (dominant) • Nn = Normal pigmentation • nn = Albinism • About 1 in 17,000 people have some type of albinism, although up to 1 in 75 are carriers. My PHENOTYPE is Albino (or no color). My GENOTYPE is nn.

  18. TRAITa characteristicExamples:Plant size, seed color, pod shape

  19. GENE(a segment of DNA that controls traits)

  20. Above you see chromosomes. The circled area is a gene on chromosome #22. The absence of this gene causes velo-cardio-facial syndrome (VCFS) which may cause ADD and mental illness

  21. Breast Cancer and Genes

  22. ALLELES Each gene comes in different forms called alleles, so the gene that controls flower color may come in two alleles: purple and white.

  23. ALLELESdifferent forms of a gene

  24. Genotype The combination of the two alleles for a given gene

  25. MENDEL’S EXPERIMENTS

  26. GREGOR MENDEL • The “father” of Genetics • Lived from 1822-1884 • Austrian Monk • Published his work in 1866, but no one took him seriously until 1900. • Studied Pea Plants!

  27. Mendel experimented with 7 different characteristics

  28. GENES Each feature of the pea plants is controlled by a gene. It may have a gene that controls its color, another size for and another for shape.

  29. Monohybrid cross. • First, Mendel kept all the traits the same except for _one___. This is a called a __monohybrid___cross___ ________ • One trait disappeared in the _F1_______ • It reappear in the F2 in a ratio of 3:1_____

  30. Dihybrid Cross • Next, Mendel controlled all traits except for __2__. He called this a _dihybrid cross_____ • Again, two traits disappeared in the F1 • They reappeared in the F2 in a ratio of 9:3:3:1

  31. Mendel’s Principles of Inheritance • Inherited traits are transmitted by genes which occur in alternate forms called alleles • Principle of Dominance - when 2 forms of the same gene are present the dominant allele is expressed • Principle of Segregation - in meiosis two alleles separate so that each gamete receives only one form of the gene • Principle of Independent Assortment - each trait is inherited independent of other traits (chance)

  32. If we saw an organism that had round seeds (round is dominant), how could we figure out what its genotype is?

  33. Test Cross A cross between an unknown and a homozygous recessive

  34. Example of a Test Cross Unknown

  35. Incomplete Dominance When a combination of the dominant and recessive creates a new phenotype. RR = red, rr = white, and Rr = pink

  36. Incomplete Dominance RR Rr rr

  37. Co-dominance When both traits are expressed equally. Example: AB blood type

  38. Sex Linked Trait a trait that is found on either the X or Y chromosome

  39. Hemophilia is an example of a sex linked trait.

  40. Hemophilia a disease where your blood doesn’t clot.

  41. Hemophilia only occurs when all of the X chromosomes have a copy of the recessive gene.

  42. SICKLE CELL ANEMIA

  43. Why would African American’s be so much more likely to have Sickle Cell?

  44. PEDIGREE chart that shows the relationships within a family

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