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Heredity

Heredity. Mendel’s Laws. Heredity. Source: http://en.wikipedia.org/wiki/Habsburg. How are traits inherited?. Selective Breeding Domestication of plants Higher yielding crops Mature faster, set fruit earlier Attractive fruit Domestication of animals Desired behaviors Desired qualities.

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Heredity

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  1. Heredity Mendel’s Laws S-B-8-1_Heredity PowerPoint

  2. Heredity S-B-8-1_Heredity PowerPoint Source: http://en.wikipedia.org/wiki/Habsburg

  3. How are traits inherited? • Selective Breeding • Domestication of plants • Higher yielding crops • Mature faster, set fruit earlier • Attractive fruit • Domestication of animals • Desired behaviors • Desired qualities Gray Wolf S-B-8-1_Heredity PowerPoint http://animal.discovery.com/mammals/wolf/ http://www.akc.org/breeds/

  4. Gregor Mendel • Born in 1822, Brno, Moravia (now the Czech Republic), the only son of a farming family • Showed promise in school and entered the monastery to continue his education • Went to the University of Vienna, studying physics and math • Came back to the Abbey in Brno to teach and experiment in the garden S-B-8-1_Heredity PowerPoint

  5. How can we calculate the probability of traits being inherited? • Sum Law • Product Law http://farm1.static.flickr.com/231/464511629_d09fb664af.jpg S-B-8-1_Heredity PowerPoint

  6. Product Law • States that the probability of two independent events occurring simultaneously is equal to the product of the probabilities of each event occurring alone. Example: • What is the probability of a coin toss resulting in 2 consecutive heads? S-B-8-1_Heredity PowerPoint

  7. Product Law Example Answer: The probability for each toss individually resulting in heads is 1/2. To obtain the probability of two consecutive heads, multiply their individual probabilities. (1/2) × (1/2) = 1/4 S-B-8-1_Heredity PowerPoint

  8. Sum Law: • States that the probability of two independent events occurring simultaneously is equal to the product of the probabilities of each event occurring alone. Example: • What is the probability if we flip a coin twice, that it will result in heads one time, and tails the next, if we do not specify the order in which they come? S-B-8-1_Heredity PowerPoint

  9. Sum Law Example Answer: • There are two mutually exclusive ways this can occur: • Heads the first time, tails the second. • Tails the first time heads the second. • The probability for each event is ½. • The probability of each situation can be derived using the product law: (1/2) × (1/2) = 1/4 • Since the individual events are mutually exclusive, the total probability of either occurring can be derived using the sum law: (1/4) + (1/4) = 1/2 S-B-8-1_Heredity PowerPoint

  10. Mendel’s Experiment • Mendel investigates inheritance in pea plants for eight years. • He chose peas because: • They are easy to cultivate. • They reproduced sexually. • They have easy to distinguish traits. http://www.scientificamerican.com/article.cfm?id=gene-behind-mendels-green&ref=rss S-B-8-1_Heredity PowerPoint

  11. Pisum sativum-The Pea http://www.tutorvista.com/content/biology/biology-iii/heredity-and-variation/mendels-experiments.php S-B-8-1_Heredity PowerPoint

  12. THINK-PAIR-SHARE • What made Gregor Mendel uniquely qualified for his experiments in heredity? • Pea plants have more than 7 observable traits. What condition did the trait need to meet in order for Mendel to study it? http://commons.wikimedia.org/wiki/File:Gregor_Johann_Mendel_bust.jpg S-B-8-1_Heredity PowerPoint

  13. Artificial Pollination Removing Stamen from flower Exposing Stigma and dusting with pollen Covering the flower with bag and labeling stem S-B-8-1_Heredity PowerPoint

  14. X Monohybrid Cross • Crossed Tall plants with Short plants, the parents or P • Called the hybrid offspring, the First Filial, F1, generation What would you expect the F1 Generation to look like? P F1 All offspring are tall. S-B-8-1_Heredity PowerPoint

  15. Rule of Dominance • DOMINANT traits • The trait expressed in hybrid offspring, the F1 generation • recessive traits • The trait that is not expressed, or hidden, in the F1 generation S-B-8-1_Heredity PowerPoint

  16. Biggest toe longest Longer second toe Widow’s Peak Attached Earlobe Smile Straight thumb Hitchhiker’s thumb Rolling tongue Kinky/naturally curly hair Non-rolling tongue Straight or wavy hair No Widow’s Peak Free Earlobe http://www.naturallycurly.com/curlreading/curl-products/curl-expert-creates-hair-rules-line-for-curls-and-kinks No Dimples https://mrsmaine.wikispaces.com/Jade+D Dimples http://udel.edu/~mcdonald/mythtongueroll.html http://udel.edu/~mcdonald/mythearlobe.html http://www.nydailynews.com/lifestyle/2010/06/09/2010-06-09_new_cosmetic_surgery_dimpleplasty_gives_you_dimples_like_mario_lopezs_in_ten_min.html No mid-digit hair Mid-digit hair https://mrsmaine.wikispaces.com/Jade+D Dominant/Recessive People Search S-B-8-1_Heredity PowerPoint http://www.ncrtec.org/tl/camp/gene/thumbs.htm

  17. X 787 tall plants and 277 dwarf plants The F2 Generation Mendel allowed the F1 plants to self pollinate. What would you expect the offspring to look like? P F1 F2 S-B-8-1_Heredity PowerPoint

  18. X P F1 F2 Rule of Unit Factors Mendel’s Explanation • Individuals have two “heritable” factors for a trait . • The two factors may or may not contain the same information: • Homozygous individuals have identical factors . • TT or tt • Heterozygous individuals have 2 different factors. • Tt TT tt Tt TT Tt Tt tt S-B-8-1_Heredity PowerPoint

  19. Dwarf allele Genetics Modern Genetics • Individuals have two copies of a gene (one one each homologous chromosome). • The various forms of a gene are called alleles: • Dominant alleles are expressed when they are present. • Recessive alleles are expressed only when the individual is homozygous for the gene form. Tall allele Genes at the same location HOMOLOGOUS CHROMOSOMES S-B-8-1_Heredity PowerPoint

  20. Phenotypes refer to what is expressed or the organism’s outward appearance. TT and Tt pea plant will be over 6 feet tall. tt pea plant will be under 2 feet tall. Genotypes refers to the specific alleles that make up the organism. A TT pea plant is homozygous Tall while a tt pea plant is homozygous dwarf. A Tt pea plant is heterozygous Tall. Phenotypes vs. Genotypes S-B-8-1_Heredity PowerPoint

  21. THINK-PAIR-SHARE • If the black rabbit and the white rabbit were bred and all the offspring were black, what conclusion can you make? • If the hybrid offspring were allowed to mate, would you expect some of the litter to be white? Why? http://www.countryfarm-lifestyles.com/raising-rabbits.html X http://athomepets.blogspot.com/2008/03/bunnies-born-for-easter-crowd.html S-B-8-1_Heredity PowerPoint

  22. THINK-PAIR-SHARE • Are the genotypes homozygous dominant, homozygous recessive, or heterozygous? • DdFF • RrYy • LLww • ggSs • The letters used in genotypes usually represent the dominant trait, e.g., Y-yellow seed and y-green seed. Decide on traits to represent the genotypes above, and describe the phenotypes. S-B-8-1_Heredity PowerPoint

  23. Mendel’s Explanation Alleles separate when forming gametes. Parents pass only one allele for each trait. Modern Genetics What process ensures that alleles separate during gamete formation? Law of Segregation S-B-8-1_Heredity PowerPoint http://www-bcf.usc.edu/~forsburg/meiosis.html

  24. P X F1 Dihybrid Cross • Mendel repeated his experiment with plants that are bred true for two traits. • He again allowed the F1 generation to self pollinate. • Phenotypic ratio: 9:3:3:1 F2 32 315 108 101 R-Round r-wrinkled Y-Yellow y-green http://image.wistatutor.com/content/feed/u2044/Punnet%20square.gif S-B-8-1_Heredity PowerPoint

  25. Law of Independent Assortment Mendel’s Explanation • Traits are inherited independently from one another. • Modern Genetics • What process ensures that genes are randomly assorted among the gametes? S-B-8-1_Heredity PowerPoint http://www.palaeos.com/Fungi/Lists/Glossary/GlossaryM.html

  26. Punnett Squares Punnett Square of Dihybrid Cross • British biologist Reginald Punnett used a matrix to show the Laws of Segregation and Independent Assortment. • The Punnett Square shows the probability of an offspring having a particular genotype. Parent Genotype RrYy Gametes’ Genotype Gametes’ Genotype S-B-8-1_Heredity PowerPoint http://image.wistatutor.com/content/feed/u2044/Punnet%20square.gif

  27. Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? Both parents are hybrids or heterozygous for black fur. ♂Bb and ♀Bb Step 1 Write the genotypes of the parents. S-B-8-1_Heredity PowerPoint

  28. STEP 2 List the different gametes that each parent can make. Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? To find the number of different gametes is 2n,wherenis the number of heterozygous gene pairs ♂ gametes ♀gametes B and b B and b S-B-8-1_Heredity PowerPoint

  29. STEP 3 Make a grid of horizontal and vertical lines. Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? Since the male and female can make 2 different gametes the grid will be 2 x 2. S-B-8-1_Heredity PowerPoint

  30. ♂gametes STEP 4 Put the gametes from one parent on the top and the other parent’s gametes on the side. ♀ gametes Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? B b B b S-B-8-1_Heredity PowerPoint

  31. STEP 5 Fill in the boxes by copying the row and column headings. B b B b Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? BB Bb Bb bb S-B-8-1_Heredity PowerPoint

  32. STEP 6 Determine the phenotypes of the possible offspring. B b BB Bb BB Bb B b } Bb bb 3-Black colored fur 1-Tan colored fur Using Punnett Squares Black colored fur (B) is dominant to tan colored fur (b) in dogs. Suppose you cross two hybrid dogs with black fur. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? 1-BB 2-Bb 1-bb S-B-8-1_Heredity PowerPoint

  33. THINK-PAIR-SHARE • What would a Punnett square look like for a monohybrid cross of a purple flowered pea plant allowed to self pollinate? • What are the genotypic ratios of the monohybrid cross? S-B-8-1_Heredity PowerPoint http://en.wikipedia.org/wiki/File:Punnett_square_mendel_flowers.svg

  34. Problems with Two Traits Black colored fur (B) is dominant to tan colored fur (b) in dogs while smooth hair (h) is recessive to wire hair texture (H). Suppose you cross two hybrid dogs with black wiry coats. What are the possible phenotypes and genotypes of the puppies? What are the expected ratios for each genotype and phenotype? Both parents are hybrids or heterozygous for black and wiry coats. Step 1 Write the genotypes of the parents. ♂BbHh and ♀BbHh S-B-8-1_Heredity PowerPoint

  35. Problems with Two Traits Step 1 Write the genotypes of the parents. ♂BbHh and ♀BbHh BH, Bh, bH, bh ♂ gametes BH, Bh, bH, bh ♀ gametes STEP 2 List the different gametes that each parent can make. bh BH, Bh bH ♂ gametes S-B-8-1_Heredity PowerPoint

  36. Problems with Two Traits STEP 3 Make a grid of horizontal and vertical lines. ♂ gametes BH Bh bH bh STEP 4 Put the gametes from one parent on the top and the other parent’s gametes on the side. ♀ gametes S-B-8-1_Heredity PowerPoint

  37. ♂ gametes BH Bh bH bh BH Bh bH bh ♀ gametes Problems with Two Traits STEP 5 Fill in the boxes by copying the row and column headings. BbHh BBHH BBHh BbHH BBHh BBhh BbHh Bbhh bbHH bbHh BbHH BbHh BbHh Bbhh bbHh bbhh S-B-8-1_Heredity PowerPoint

  38. Problems with Two Traits STEP 6 Determine the phenotypes of the possible offspring. There is a 9 out of 16 chance that the offspring will have a black wiry coat. BBHH BBHh BBHh BbHH BbHH BbHh BbHh BbHh BbHh There is a 3 out of 16 chance that the offspring will have a black smooth coat. Bbhh Bbhh BBhh There is a 3 out of 16 chance that the offspring will have a wiry tan coat. bbHh bbHh bbHH There is a 1 out of 16 chance that the offspring will have a smooth tan coat bbhh S-B-8-1_Heredity PowerPoint

  39. THINK-PAIR-SHARE In guinea pigs, short hair (H) is dominant to long hair (h) and a short tail (T) is dominant to long tails (t). If a hybrid short hair and tail guinea pig is crossed with a long hair and tail guinea pig, what are the expected genotypic and phenotypic ratios? S-B-8-1_Heredity PowerPoint

  40. Hybrid gametes Purebred gametes HT, Ht, hT, ht ht Hybrid parent Purebred Parent HhTt hhtt Step 1: Step 2: Ht hT ht Step 3: HT Step 4: HhTt ht Hhtt hhTt hhtt Step 5: There is a 1 in 4 chance that the offspring will have short hair and tail Step 6: HhTt There is a 1 in 4 chance that the offspring will have short hair and a long tail Hhtt hhTt There is a 1 in 4 chance that the offspring will have long hair and a short tail hhtt There is a 1 in 4 chance that the offspring will have long hair and tail S-B-8-1_Heredity PowerPoint

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