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GENETICS Ch. 11

GENETICS Ch. 11. Gregor Mendel. Genetics is the study of heredity . Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breeding garden peas . 2. Mendel cross-pollinated pea plants.

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GENETICS Ch. 11

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  1. GENETICSCh. 11

  2. Gregor Mendel • Genetics is the study of heredity. • Gregor Mendel (1860’s) discovered the fundamental principles of genetics by breedinggarden peas.

  3. 2. Mendel cross-pollinated pea plants • He cut away the male parts of one flower, then dusted it with pollen from another

  4. 3. What did Mendel conclude? • He concluded that factors are passed from one generation to the next.

  5. eye color locus B = brown eyes eye color locus b = blue eyes Paternal Maternal 4. The Principle of Dominance • Alleles 1. Alternative forms of genes. 2. Units that determine heritable traits. The Principle of Dominance – some alleles are dominant and other are recessive.

  6. 5. Dominant and Recessive alleles Dominant alleles – upper-case a. homozygous dominant (BB – Brown eyes) Recessive alleles – lower case a. homozygous recessive (bb – blue eyes) b. Heterozygous (Bb – Brown eyes)

  7. Outward appearance Physical characteristics Examples: 1.Brown eyes 2.blue eyes Arrangement of genes that produces the phenotype Example: 1. TT, Tt 2. tt Phenotype vs. Genotype

  8. 6. SegregationAlleles separate during meiosis

  9. 7. Recessive traits show up about 1/4th of the time. • Because there is only a 25% chance that two recessive alleles will be paired together.

  10. 9. Punnett square • A Punnett square is used to show the possible combinations of gametes. • Monohybrid Cross

  11. B b male gametes B Bb x Bb b female gametes Monohybrid Cross • Example: Cross between two heterozygotesfor brown eyes (Bb) BB = brown eyes Bb = brown eyes bb = blue eyes

  12. B b 1/4 = BB - brown eyed 1/2 = Bb - brown eyed 1/4 = bb - blue eyed BB Bb B Bb x Bb b Bb bb 1:2:1 genotype 3:1 phenotype Monohybrid Cross

  13. Dihybrid Cross

  14. RY Ry rY ry RY Ry rY ry Dihybrid Cross

  15. RY Ry rY ry Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 RY RRYY RRYy RrYY RrYy Ry RRYy RRyy RrYy Rryy rY RrYY RrYy rrYY rrYy ry RrYy Rryy rrYy rryy 9:3:3:1 phenotypic ratio Dihybrid Cross

  16. RY Ry rY ry x RY Ry rY ry possible gametes produced Dihybrid Cross • Example: cross between round and yellow heterozygous pea seeds. R = round r = wrinkled Y = yellow y = green RrYy x RrYy

  17. This means all gametes will be different! B sperm B B Bb haploid (n) b b diploid (2n) b meiosis II meiosis I 10. Independent Assortment B F • Chromosomes separate independently of eachother Bb Ff b f Bb Ff B f Bb Ff B F

  18. Independent Assortment • Genes for different traits can segretate independently during the formation of gametes without influencing eachother • Question: How many gametes will be produced for the following allele arrangements? • Remember: 2n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtQq

  19. Answer: 1. RrYy: 2n = 22= 4 gametes RY Ry rY ry 2. AaBbCCDd: 2n = 23= 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3. MmNnOoPPQQRrssTtQq: 2n = 26= 64 gametes

  20. R R produces the F1 generation Rr Rr r r Rr Rr All Rr = pink (heterozygous pink) 11. Incomplete Dominance • One allele is not completely dominant over another

  21. 11. Codominance • Both alleles are expressed • Example: blood 1. type A = IAIA or IAi 2. type B = IBIB or IBi 3. type AB = IAIB 4. type O = ii Black cow + white cow = spotted cow

  22. Male CC with female Cc Male cc with female Cc c C c C C C c c 12. Which shows more genetic variation. (more combos?)

  23. Genetic Engineering

  24. Gene Therapy

  25. Is cloning a possibility? • Is it right to use cloning to create an entirely new human being? • Is it ethical to create an embryonic copy of John Doe to supply cells to keep John alive? • Does a multicellular ball of tissue -- an embryo -- have the same rights and status as a human being?

  26. How does Mendel’s principles apply to organisms • The basic principals can be applied to humans as well as any other living organism.

  27. And now it’s time for…. • Spongebob Genetics!!!!!

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