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How are genetic traits inherited?

How are genetic traits inherited?. Chapter 10. Observing Differences. http://pantransit.reptiles.org/images/1996-07-28/parrots.jpg. http://www.paw-rescue.org/CATS/SPECIAL_USE/kittens.jpg. http://strictlyreptiles.tv/photos/gallery/a/images/Albino%20sulcata%20and%20heteros.jpg.

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How are genetic traits inherited?

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  1. How are genetic traits inherited? Chapter 10

  2. Observing Differences http://pantransit.reptiles.org/images/1996-07-28/parrots.jpg http://www.paw-rescue.org/CATS/SPECIAL_USE/kittens.jpg http://strictlyreptiles.tv/photos/gallery/a/images/Albino%20sulcata%20and%20heteros.jpg http://www.wyomingoutdoorsradio.com/Copy%20of%20Albino%20bear%202.jpg http://www.englishbulldogminiature.com/webart/P1-24.jpg http://www.ravenna.portage.k12.oh.us/schools/willyard/hamsters/inbowl.jpg

  3. Observing Differences • Inherited traits are passed from the parent generation to the offspring. • Typically called genes • What are some inherited traits in humans? • Acquired traits are characteristics accumulated through out an individual’s lifetime. • Not passed on to a individual’s offspring. • What are some acquired traits in humans? http://www.phschool.com/atschool/science_activity_library/images/survey_of_traits.jpg

  4. The Science of Genetics • Genetics is the scientific study of heredity. • Heredity is the passing on of characteristics from parents to offspring. • These characteristics that are passed on are called traits. http://www.atmos.washington.edu/2001Q1/211/Group_projects/group_Y_W01/Mitchel/ClimateAgriculture_files/image002.jpg

  5. Gregor Mendel observed the heritable traits of pea plants. Obtained large amounts of data to find the probability of certain traits. Grew many generations of pea plants and measured there traits. Mendel carefully followed one trait at a time to compile his results. The Science of Genetics http://www.library.villanova.edu/services/exhibits/images/mendel.JPG

  6. Why Pea Plants? Pea plants reproduce sexually. They produce male and female sex cells, or gametes. The male gamete is the pollen. Fertilization results in a zygote that develops into a seed. Pea Plant Experiments http://en.wikipedia.org/wiki/Image:Crateva_religiosa.jpg http://freepages.family.rootsweb.com/~bobofwa/gardenpea.jpg

  7. Pollination occurs when the pollen grains are transferred to the female sex organ. Pea plants contain both sex organs in the same flower. Pea plants usually reproduce through self-pollination. Pea Plant Experiments http://fairmanstudios.com/images/pollination.jpg

  8. Sometimes, Mendel wanted to breed one plant with another. Called cross-fertilization. He remove the male organs. He would dust the pollen from one flower onto the female parts of another flower. Pea Plant Experiments http://www.usask.ca/biology/rank/genomic/mendel1.jpg

  9. Mendel carefully studied one trait at a time. He examined seven traits of pea plants: Pea Plant Experiments

  10. Pea Plant Experiments Round vs. Wrinkled Yellow vs. Green

  11. P1 Generation Mendel needed to begin with true breeding parent plants. Tall plants that only have tall offspring Short plants that only have short offspring Mendel’s Monohybrid Crosses http://www.glencoe.com/qe/images/b136/q4315/ch10_0_h.gif

  12. F1 Generation Mendel crossed the true-breeding tall pea plant with the true-breeding short pea plant. All offspring where as tall as the tall parent plant. A hybrid is produced by fertilizing different lines with each other. Mendel’s Monohybrid Crosses http://www.glencoe.com/qe/images/b136/q4315/ch10_0_h.gif

  13. F2 Generation When Mendel allowed the offspring to reproduce, he found: Most of the plants were tall But the short trait returned in ¼ of the offspring. Mendel’s Monohybrid Cross http://www.glencoe.com/qe/images/b136/q4315/ch10_0_h.gif

  14. Mendel’s Monohybrid Crosses • Mendel continued his research with the other traits of pea plants with similar results. • He made several important conclusions: • The Rule of Unit Factors • The Rule of Dominance • The Rule of Segregation • The Rule of Independent Assortment http://home.hawaii.rr.com/mwh8000/BioWebProject/Mendels_Pea_Plants.JPG

  15. Actual Results of F2 Cross

  16. Each organism contains two factors that control each of its traits. One factor from the mother and the other from the father. These factors are called genes, which determine your traits. Genes are pieces of DNA that code for a specific protein, which are located on a chromosome. The Rule of Unit Factors

  17. The Rule of Unit Factors • The multiple forms of a gene are called alleles. • The gene for seed color has two alleles: • Some are yellow • Some are green YellowvsGreen

  18. When two pure-bred plants are crossed, the hybrids will only show the trait of one allele. Dominant Allele The trait that is observed in hybrids. Represented by a capital letter. Recessive Allele The trait that disappears in hybrids. Represented by a lower case letter. The Rule of Dominance Y = Yellow y = green

  19. The phenotype is the way that an organism looks. The physical appearance of a trait. The Rule of Dominance YELLOW GREEN

  20. The genotype of an organism is the combination of alleles or the genetic makeup. Homozygous If both alleles for the trait are the same. True-breeding (P1 generation) Heterozygous If the two alleles for the trait are different. Hybrids (F1 generation) Always shows the dominant phenotype. The Rule of Dominance YY yy Yy

  21. Yoga for Your Brain What word, expression, or name is depicted below? BEND DRAW DRAW DRAW agb

  22. Yoga for Your Brain What word, expression, or name is depicted below? HOROBOD MEica

  23. When the gametes are formed, the alleles separate from each other. Half of the gametes have one allele. Half of the gametes have the other allele. When fertilization occurs, each parent contributes a single allele. The Rule of Segregation

  24. Rule of Segregation P generation TT tt segregation T T t t fertilization F1 generation Tt Tt Tt Tt segregation T t T t fertilization TT Tt Tt tt F2 generation 3 Tall and 1 Short

  25. Mendel concluded that genes for different traits are inherited independently from each other. Green pea color does not mean tall plant. Forming Gametes TTYy  TY, Ty, TY, Ty TtYY  TY, tY, TY. tY TtYy  TY, Ty, tY, ty The Law of Independent Assortment Rryy rryy rryy rrYy rrYy RrYy Rryy RrYy

  26. Step One Identify what the letters mean. Step Two Determine the genotypes of the parents. Steps to a Punnett Square Y – yellow pea y – green pea X yy YY

  27. Step Three Put the parents’ gametes on the outside of the square. Steps to a Punnett Square y y X yy Y YY Y

  28. Step Four Complete the inside of the square to determine the possible combinations. Steps to a Punnett Square y y Yy Yy Y Yy Yy Y

  29. Step Five Determine the probability of each genotype. Step Six Determine the probability of each phenotype. Steps to a Punnett Square y y Yy Yy Y Genotype- 100% Yy Yy Yy Y Phenotype- 100% Yellow

  30. Y Y y Y y - yellow y - green Monohybrid Cross Heterozygous Yellow x Heterozygous Yellow Y y Y Y Y Y y Genotypic Ratio 1:2:1 Phenotypic Ratio 3:1 y Y y y y

  31. Two-Factor Cross Yyrr yyRR X Heterozygous Yellow and Wrinkled Green and Homozygous Round yR yR yR yR Results: Genotypes- 50% YyRr 50% yyRr YyRr YyRr YyRr YyRr Yr YyRr YyRr YyRr YyRr Yr Phenotypes- 50%yellow/round 50% green/round yyRr yyRr yyRr yyRr yr yyRr yyRr yyRr yyRr yr

  32. Dihybrid Cross YyRr Heterozygous Yellow and Heterozygous Round X Heterozygous Yellow and Heterozygous Round YyRr YR Yr yR yr YR YYRR YYRr YyRR YyRr Phenotypic Ratio: 9 Yellow/Round YYRr YYrr YyRr Yyrr Yr 3 Yellow/Wrinkled 3 Green/Round yR YyRR YyRr yyRR yyRr 1 Green/Wrinkled yr Yyrr yyRr yyrr YyRr 9:3:3:1

  33. A recessive phenotype only has one genotype. A dominant phenotype has two possible genotypes. A test cross is used to determine the genotype of a dominant phenotype. Cross the dominant individual with a recessive individual. Test Cross gg Green is Dominant GG Gg Blue is Recessive

  34. Look at the offspring A GG x gg cross only produces dominant offspring. A Gg x gg cross produces both dominant and recessive phenotypes. If any offspring are recessive (gg), then the dominant parent must have been heterozygous (Gg). Test Cross g g G Gg Gg Gg Gg Gg Gg G gg gg g If the green parent is homozygous dominant, 100% of the offspring are green. If the green parent is heterozygous dominant, 50% of the offspring will be blue!

  35. Review Questions Assuming you are not a dwarf, what is your genotype? If someone were a dwarf, what could their genotype be? If two non-dwarfs mated, what is the probability of a dwarf child? In humans, dwarfism is dominant to average height.

  36. Review Questions If two dwarfs with heterozygous genotypes mate, what is the probability of having a non-dwarf child? If a person is dwarf of unknown genotype, how can you determine his/her genotype? (Hint: You Will Perform a Test Cross) In humans, dwarfism is dominant to average height.

  37. 6 5 1 2 3 4 D? Dd Dd dd dd dd

  38. How are the Gametes Formed? Section 10.2

  39. Section Objectives • At the end of this lesson, YOU will be able to: • Analyze how meiosis maintains a constant number of chromosomes within a species. • Infer how meiosis leads to variation in species. • Relate Mendel’s laws of heredity to the events of meiosis.

  40. Remember Mitosis • In the human body, somatic (body) cells have 46 chromosomes. • These cells undergo mitosis to create 2 identical cells, each with the same 46 chromosomes. • The purpose of mitosis is the grow and replace old cells. • Somatic cells are diploid. • This means that each chromosome has an identical copy. • Humans have 46 chromosomes, or 23 pairs. • Diploid is represented by 2N.

  41. 2N 4N 2N 2N Remembering Mitosis 46 S phase iPMATc 46 92 Diploid 46 Diploid

  42. Gametes • In the human body, gametes (sex cells) have 23 chromosomes. • These cells undergo meiosis to create 4 different daughter cells, each with 23 chromosomes. • Gametes are haploid. • This means that the cells have half the normal number of chromosomes. • Haploid is represented by N.

  43. N 2N N S phase 2N 4N Meiosis II Meiosis I N 2N N Meiosis Diploid Haploid

  44. A Connection to Mendel • Mendel’s Rule of Unit Factors • Mendel said that each organism has two alleles for a trait. • This is supported by the diploid nature of body cells. • Mendel’s Rule of Segregation • Mendel said that each parent gives one allele to the offspring. • This is supported by the haploid nature of the reproductive cells. Aa Aa Aa a a A A Aa a A Aa a A A A a a Nothing to Write on this Slide!

  45. Chromosome Numbers • Each species contains a specific number of chromosomes. • The number of chromosomes in the gametes is exactly half the number in body cells. • The number of chromosomes does not relate to the complexity of the organism.

  46. In a diploid cell, the two chromosomes that are paired are called homologous chromosomes. Each of the pair have the same genes arranged in the same order. The chromosomes may have different forms of a gene (alleles). Homologous Chromosomes

  47. Meiosis is a form of cell division that produces gametes containing half the number of chromosomes as a parent’s body cell. Meiosis occurs in specialized cells that produce gametes. The gametes are haploid cells. The male gamete is sperm. The female gamete is egg. Meiosis

  48. Human Meiosis

  49. Fertilization occurs when a sperm cell unites with an egg cell. The resulting zygote has a diploid number of chromosomes. This is called Sexual Reproduction. Sperm (23) + Egg (23) = Zygote (46) Fertilization

  50. Meiosis consists of two consecutive cell divisions to produce gametes. Meiosis I Meiosis II The Phases of Meiosis

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