1 / 30

Mendelian Patterns of Inheritance

Mendelian Patterns of Inheritance. Outline. Blending Inheritance Monohybrid Cross Law of Segregation Modern Genetics Genotype vs. Phenotype Punnett Square Dihybrid Cross Law of Independent Assortment. Gregor Mendel.

dutch
Télécharger la présentation

Mendelian Patterns of Inheritance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mendelian Patterns of Inheritance Mader: Biology 8th Ed.

  2. Outline • Blending Inheritance • Monohybrid Cross • Law of Segregation • Modern Genetics • Genotype vs. Phenotype • Punnett Square • Dihybrid Cross • Law of Independent Assortment Mader: Biology 8th Ed.

  3. Gregor Mendel • Austrian monk who formulated fundamental laws of heredity in early 1860s. • Studied science and mathematics at University of Vienna. • Conducted breeding experiments with the garden pea Pisum sativum. • Carefully gathered and documented mathematical data from his experiments. Mader: Biology 8th Ed.

  4. Blending Inheritance • At the time, most breeders believed parents of contrasting appearance always produce offspring of intermediate appearance. • Mendel’s experiments helped him formulate the particulate theory of inheritance. • Inheritance involves reshuffling of genes from generation to generation. Mader: Biology 8th Ed.

  5. Garden Peas Mader: Biology 8th Ed.

  6. One-Trait Inheritance • Mendel performed cross-breeding experiments between true-breeding plants. • Chose varieties that differed in only one trait (monohybrid cross) • Performed reciprocal crosses • Parental generation = P • First generation offspring = F1 • Second generation offspring = F2 • Formulated law of segregation Mader: Biology 8th Ed.

  7. Mendel’s Monohybrid Cross Mader: Biology 8th Ed.

  8. Mendel’s Monohybrid Cross Mader: Biology 8th Ed.

  9. Law of Segregation • Each individual has two factors for each trait. • The factors segregate during gamete formation. • Each gamete contains only one factor from each pair of factors. • Fertilization gives each new individual two factors for each trait. Mader: Biology 8th Ed.

  10. Modern Genetics View • Each trait in a pea plant is controlled by two alleles (alternate forms of a gene). • Dominant allele (capital letter) masks the expression of the recessive allele (lower-case). • Alleles occur on a homologous pair of chromosomes at a particular gene locus. • Homozygous = identical alleles • Heterozygous = different alleles Mader: Biology 8th Ed.

  11. Homologous Chromosomes Mader: Biology 8th Ed.

  12. Genotype Versus Phenotype • Genotype • Refers to the alleles an individual receives at fertilization. • Phenotype • Refers to the physical appearance of the individual. Mader: Biology 8th Ed.

  13. Punnett Square • All possible kinds of sperm are lined up on one axis, and all possible kinds of eggs are lined up on the other axis. • Every possible combination of alleles is placed within the squares. Mader: Biology 8th Ed.

  14. PUNNETT SQUARE Mader: Biology 8th Ed.

  15. Testcross • A monohybrid testcross is used to determine if an individual with the dominant phenotype is homozygous dominant or heterozygous for a particular trait. • The individual with the dominant trait in question is crossed with a homozygous recessive Mader: Biology 8th Ed.

  16. Testcross Mader: Biology 8th Ed.

  17. Two-Trait Inheritance • Mendel performed cross using true-breeding plants differing in two traits. • Dihybrid Cross • Observed phenotypes among F2 plants. • Formulated law of independent assortment Mader: Biology 8th Ed.

  18. Law of Independent Assortment • Each pair of factors segregates independently of the other pairs. • All possible combinations of factors can occur in the gametes. Mader: Biology 8th Ed.

  19. Dihybrid Cross Mader: Biology 8th Ed.

  20. Dihybrid Cross Mader: Biology 8th Ed.

  21. Two-Trait Testcross • A two-trait testcross is used to determine if an individual is homozygous dominant or heterozygous for either of the two traits. Mader: Biology 8th Ed.

  22. Two-Trait Testcross Mader: Biology 8th Ed.

  23. Incomplete Dominance • Exhibited when the heterozygote has an intermediate phenotype between that of either homozygote. Mader: Biology 8th Ed.

  24. Incomplete Dominance Mader: Biology 8th Ed.

  25. Polygenic Inheritance • Occurs when a trait is governed by two or more sets of alleles. • Each dominant allele has a quantitative effect on the phenotype, and these effects are additive. • Result in continuous variation of phenotypes. Mader: Biology 8th Ed.

  26. Height in Human Beings Mader: Biology 8th Ed.

  27. Terminology • Pleiotropy - A gene that affects more than one characteristic of an individual. • Sickle-cell anemia (incomplete dominance) • Codominance - More than one allele is fully expressed. • ABO blood type (multiple allelic traits) • Epistasis - A gene at one locus interferes with the expression of a gene at a different locus. • Human skin color (polygenic inheritance) Mader: Biology 8th Ed.

  28. Environment and Phenotype • Himalayan Rabbits - Enzyme coding for black fur is active only at low temperatures. • Black fur only occurs on extremities. Mader: Biology 8th Ed.

  29. Review • Blending Inheritance • Monohybrid Cross • Law of Segregation • Modern Genetics • Genotype vs. Phenotype • Punnett Square • Dihybrid Cross • Law of Independent Assortment Mader: Biology 8th Ed.

  30. Mader: Biology 8th Ed.

More Related