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Mendelian Genetics

Mendelian Genetics. Sexual Reproduction and Genetics. Chapter 10. 10.2 Mendelian Genetics. How Genetics Began. Inheritance, or heredity  passing traits to the next generation. Mendel performed cross-pollination in pea plants. Mendel followed various traits in the pea plants he bred.

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Mendelian Genetics

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  1. Mendelian Genetics

  2. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics How Genetics Began • Inheritance, or heredity passing traits to the next generation • Mendel performed cross-pollination in pea plants. • Mendel followed various traits in the pea plants he bred.

  3. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics • The parent generation is also known as the P generation.

  4. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics • The offspring of this P cross are called the first filial (F1) generation. • The second filial (F2) generation is the offspring from the F1 cross.

  5. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics • Mendel studied seven different traits. • Seed or pea color • Flower color • Seed pod color • Seed shape or texture • Seed pod shape • Stem length • Flower position

  6. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Genes in Pairs • Allele • An alternative form of a trait • Ex. Eye color

  7. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Dominance • Homozygous 2 of the same alleles for a particular trait, also called pure bred. • Heterozygous 2 different alleles for a particular trait, also called hybrids. Bb bb BB

  8. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Genotype and Phenotype • Genotype allele pairs (GENES) • TT, Tt, BB, bb, Mm • Phenotype The observable characteristic or outward expression of an allele pair (WHAT YOU SEE) Bb

  9. Dominant The phenotype of the organism is determined completely by one of the alleles Written with at least 1 capital letter (TT or Tt) Recessive The other allele, has no big effect on the organism's phenotype Written with lowercase letters (bb) Dominant vs. Recessive Example: Brown eyes is dominant and blue eyes is recessive

  10. Mendel’s Conclusions cont’d… Ex. Tall plant (T) x short plant (t) = tall offspring (Tt) What allele was dominant?

  11. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Mendel’sLaw of Segregation • Two alleles for each trait separate during meiosis. • During fertilization, two alleles for that trait unite.

  12. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Monohybrid Cross • A cross that involves hybrids for a single trait is called a monohybrid cross.

  13. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Dihybrid Cross • The simultaneous inheritance of two or more traits in the same plant is a dihybrid cross. • Dihybrids are heterozygous for both traits.

  14. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Law of Independent Assortment • Random distribution of alleles occurs during gamete formation • Genes on separate chromosomes sort independently during meiosis. • Each allele combination is equally likely to occur. Law of Segregation • The two alleles for each trait separate during meiosis (ex: If a parent is Tt, then either T or t can be given to the offspring)

  15. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Punnett Squares • Predict the possible offspring of a cross between two known genotypes

  16. Monohybrid Crosses Do this on your paper: Tt X Tt Cross: Give the genotypes, phenotypes, & percentages Go to Section:

  17. Monohybrid Cross Answer… Go to Section:

  18. Probability the chance or percentage of chance of a trait being exhibited

  19. Sexual Reproduction and Genetics Chapter 10 10.2 Mendelian Genetics Punnett Square—Dihybrid Cross • Four types of alleles from the male gametes and four types of alleles from the female gametes can be produced. • The resulting phenotypic ratio is 9:3:3:1.

  20. Sexual Reproduction and Genetics Chapter 10 10.3 Gene Linkage and Polyploidy Genetic Recombination • The new combination of genes produced by crossing over and independent assortment

  21. Sexual Reproduction and Genetics Chapter 10 10.3 Gene Linkage and Polyploidy Gene Linkage • The linkage of genes on a chromosome results in an exception to Mendel’s law of independent assortment because linked genes usually do not segregate independently.

  22. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Incomplete Dominance • The heterozygous phenotype is an intermediate phenotype between the two homozygous phenotypes.

  23. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Codominance • Both alleles are expressed in the heterozygous condition.

  24. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Coat Color of Rabbits • Multiple alleles can demonstrate a hierarchy of dominance. • In rabbits, four alleles code for coat color: C, cch, ch,and c.

  25. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Coat Color of Rabbits Chinchilla Albino Light gray Dark gray Himalayan

  26. Complex Inheritance and Human Heredity Chapter 11 11.2 Complex Patterns of Inheritance Multiple Alleles • Blood groups in humans • ABO blood groups have three forms of alleles.

  27. Human Blood Typing • Human blood is classified according to the presence or absence of certain markers called antigens that are located on the surface of red blood cells. • If you have the A antigen, you have type A blood and antibodies against B blood. • If you have the B antigen, you have type B blood and antibodies against A blood.

  28. What about O & AB? • If you don’t have either the A or B antigen, you have type O blood. • In the US, O is the most common blood type. • You have antibodies against A and B. • You are also a universal donor. (You can give blood to anyone) • If you have both the A and B antigens, you have type AB blood and this is the rarest form of blood. No antibodies against either A or B.

  29. Describe sex-linked alleles • Sex-linked alleles: controlled by genes located on sexchromosomes • Usually carried on X chromosome • Since females are XX, they are usually carriers of the trait • Since males are XY, they have a higher tendency for inheritance of trait

  30. Polyploidy is the occurrence of one or more extra sets of all chromosomes in an organism. Sexual Reproduction and Genetics • A triploid organism, for instance, would be designated 3n, which means that it has three complete sets of chromosomes. Chapter 10 10.3 Gene Linkage and Polyploidy

  31. Complex Inheritance and Human Heredity Chapter 11 11.3 Chromosomes and Human Heredity Karyotype Studies • Karyotype—micrograph in which the pairs of homologous chromosomes are arranged in decreasing size. • Images of chromosomes stained during metaphase • Chromosomes are arranged in decreasing size to produce a micrograph.

  32. Sexual Reproduction and Genetics Chapter 10 10.3 Gene Linkage and Polyploidy • Epistasis- is a gene at one location on a chromosome can affect the expression of a gene at a second location A good example of epistasis is the genetic interactions that produce coat color in horses and other mammals. In horses, brown coat color (B) is dominant over tan (b). Gene expression is dependent on a second gene that controls the deposition of pigment in hair.

  33. Genetics Disorders

  34. Recessive

  35. Cystic Fibrosis • Affects the mucus-producing glands, digestive enzymes, and sweat glands

  36. Albinism • Caused by altered genes, resulting in the absence of the skin pigment melanin in hair and eyes • White Hair • Very pale skin • Pink Pupils

  37. Tay-Sachs • Causes inflating of brain nerve cells and mental deterioration. • Most common in Jewish descent people

  38. Dominant

  39. Huntington’s Disease • Decline in nervous system functions & causes mental retardation • Ability to move deteriorates

  40. Achondroplasia • small body size and limbs that are comparatively short

  41. Sex-Linked (On X Chromosome)

  42. Describe sex-linked alleles • Sex-linked alleles: controlled by genes located on sexchromosomes • Usually carried on X chromosome • Since females are XX, they are usually carriers of the trait • Since males are XY, they have a higher tendency for inheritance of trait

  43. Hemophilia

  44. Red-Green Color-Blindness

  45. Co-Dominant

  46. Sickle Cell Anemia Changes in hemoglobin cause red blood cells to change to a sickle shape.

  47. Non-Disjunction

  48. Klinefelter Syndrome • Male • Extra X-chromosome • Genotype: XXY • Sterile • Often mentally retarded • Small testes, enlarged breasts, and reduced sperm production

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