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TOPIC D: HEREDITY

TOPIC D: HEREDITY. CHAPTER 11-1,11-2,11-3. Genetics The study of heredity 1. Gregor Mendel, the “Father of Genetics”, was an monk in the 1860’s who discovered the fundamental principles of genetics by breeding garden peas. Genes and Alleles. Genes

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TOPIC D: HEREDITY

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  1. TOPIC D: HEREDITY CHAPTER 11-1,11-2,11-3

  2. Genetics The study of heredity 1. Gregor Mendel, the “Father of Genetics”, was anmonk in the 1860’s who discovered the fundamental principles of genetics by breedinggarden peas.

  3. Genes and Alleles Genes Sequence of DNA that codes for a protein and determines a trait. Alleles Alternative forms of genes. One comes from your mom and one from your dad.

  4. Multiple alleles traits that are controlled by more than two alleles (ex. ABO blood typing)

  5. eye color locus B = brown eyes eye color locus b = blue eyes Paternal Maternal 2. The Principle of Dominance Some alleles are dominant and others are recessive. Recessive alleles are not expressed in the organism, but may be passed on to future generations.

  6. 3. Dominant and Recessive alleles Dominant alleles – upper-case (BB) Recessive alleles – lower case (bb) Homozygous (purebred) both alleles are the same (BB – Brown eyes) (bb – blue eyes) Heterozygous (hybrid) two differentalleles (Bb – Brown eyes)

  7. 4. 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.

  8. Outward appearance Physical characteristics Examples: 1.Brown eyes 2.blue eyes Arrangement of genes that produces the phenotype Example: 1. BB, Bb 2. bb Genotype Phenotype

  9. Punnett Square • A Punnett square is used to show the possiblecombinations of gametes and allow us to determine the probability of an allele combination.

  10. Dihybrid Cross • cross between two individuals that differ in two traits of particular interest Example: cross between round and yellow heterozygous pea seeds.

  11. 7. What Possible Gametes are Produced in a Dihybrid Cross RY RyrYryx RY RyrYry RrYyx RrYy R = round r = wrinkled Y = yellow y = green

  12. Round/Yellow = ? Round/green = ? wrinkled/Yellow = ? wrinkled/green = ? RY Ry rY ry RY Ry rY ry 8. Dihybrid Cross

  13. Heredity Part II Intermediate (Non-Mendelian) Inheritance

  14. R R W W Incomplete Dominance • One allele is not completely dominant over another and the traits combine • RED FLOWER + WHITE FLOWER = PINK FLOWER

  15. R R RW RW W RW RW W Incomplete Doiminance a. List the possible genotypes and phenotypes genotypes – RW phenotypes – Pink b. How many of the plants would have red flowers? 0 % c. How many would have white flowers? 0% • How many would have pink flowers? 100%

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

  17. Codominance in Blood

  18. Polygenic Traits – a trait controlled by two or more than two genes (usually by many different genes) at different loci on different chromosomes Examples: skin color, shoe size

  19. Sex-linked Traits • a trait genetically determined by an allele located on the X- chromosome

  20. And now it’s time for…. • Bikini Bottom Genetics!!!!!

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