1 / 43

Unit 4 Genetics

Unit 4 Genetics. Ch. 11 Introduction to Genetics. The Work of Gregor Mendel. Genetics - the scientific study of heredity Mendel is considered the “Father” of genetics. Gregor Mendel’s Peas. Mendel was an Austrian monk, that worked on pea plants

biana
Download Presentation

Unit 4 Genetics

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. Unit 4 Genetics Ch. 11 Introduction to Genetics

  2. The Work of Gregor Mendel • Genetics - the scientific study of heredity • Mendel is considered the “Father” of genetics

  3. Gregor Mendel’s Peas • Mendel was an Austrian monk, that worked on pea plants • His experiments with pea plants laid the foundation of the science of genetics

  4. Gregor Mendel’s Peas • Fertilization - when male & female sex cells join together • Pea flowers are normally self-pollinating, meaning the sperm cells in the pollen fertilize the egg cells in the same flower

  5. Gregor Mendel’s Peas • Seeds produced by self-pollination inherit all of their characteristics from the single plant that bore them • True-breeding - if plants were allowed to self-pollinate, they would produce offspring identical to themselves

  6. Gregor Mendel’s Peas • Mendel wanted to produce seeds by joining male & female sex cells from 2 different plants • He cut off the pollen (male) parts of a plant, & dusted pollen from another plant onto the flower (female)

  7. Gregor Mendel’s Peas • Cross-pollination - produces seeds that had 2 different parent plants

  8. Genes & Dominance • P - parent generation • F1 - First generation (first generation of offspring) • F2 - Second generation (offspring from the F1 generation)

  9. Genes & Dominance • Trait - a specific characteristic • Ex.) seed color, plant height • Hybrids - offspring of crosses between parents with different traits • Ex.) cross between plant with yellow seed color & plant with green seed color

  10. Genes & Dominance • Mendel concluded that biological inheritance is determined by factors that are passed from 1 generation to the next • Genes - chemical factors that determine traits

  11. Genes & Dominance • Alleles - different forms of a gene • Ex.) gene for plant height occurs in 1 form that produces tall plants & in another form that produces short plants • Mendel’s 2nd conclusion is the principle of dominance

  12. Genes & Dominance • The principle of dominance states that some alleles are dominant & others are recessive • Dominant allele for a trait will always be exhibited (expressed or shown) • Recessive allele will only be expressed when a dominant allele is not present

  13. Mendel’s Seven F1 Crosses on Pea Plants

  14. Segregation • Gametes - sex cells (sperm or egg) • Segregation - during gamete formation, alleles segregate (separate) from each other so each gamete only carries a single copy of each gene

  15. Segregation • Therefore, each F1 plant produces 2 types of gametes, those with the allele for tallness & those with the allele for shortness

  16. Punnett Squares • Punnett square - a diagram that might result from a genetic cross • Punnett squares can be used to predict & compare the genetic variations that will result from a cross

  17. Punnett Squares • Homozygous - organisms that have 2 identical alleles for a particular trait • Ex.) TT or tt • Heterozygous - organism that has 2 different alleles for the same trait • Ex.) Tt

  18. Punnett Squares • Phenotype - physical characteristics • Ex.) Tall plants • Genotype - genetic makeup • Ex.) TT

  19. Independent Assortment • Independent assortment - genes for different traits can segregate (separate) independently during gamete formation • Independent assortment increases genetic variation (genetic diversity, helps create genetically different organisms)

  20. A Summary of Mendel’s Principles 1. The inheritance of biological characteristics is determined by individual units - genes • Genes are passed from parents to their offspring

  21. A Summary of Mendel’s Principles 2. In cases where 2 or more forms (alleles) of the gene for a single trait exist, some forms of the gene may be dominant & others may be recessive

  22. A Summary of Mendel’s Principles • 3. In most sexually producing organisms, each adult has 2 copies of each gene (1 from each parent) • These genes are segregated (separated) from each other when gametes are formed

  23. A Summary of Mendel’s Principles • 4. The alleles for different genes usually segregate (separate) independently of 1 another

  24. Beyond Dominant & Recessive Alleles • Some alleles are neither dominant nor recessive, & many traits are controlled by multiple alleles or multiple genes

  25. Beyond Dominant & Recessive Alleles • Incomplete dominance - when 1 allele is not completely dominant over another • The heterozygous phenotype is somewhere in between the 2 homozygous phenotypes

  26. Beyond Dominant & Recessive Alleles • Codominance - where both alleles contribute to the phenotype • Flowers would not be pink, (a blend of red & white), but both red & white speckled

  27. Beyond Dominant & Recessive Alleles • Multiple alleles - when genes have more than 2 alleles • It does not mean that an individual can have more than 2 alleles • It only means that more than 2 possible alleles exist in a population

  28. Multiple Alleles

  29. Beyond Dominant & Recessive Alleles • Polygenic traits - traits controlled by 2 or more genes • Ex.) at least 3 genes are responsible for making the reddish-brown pigment in the eyes of fruit flies

  30. Genetics & the Environment • The characteristics of any organism are not determined solely by the genes it inherits • Characteristics are determined by interaction between genes & the environment

  31. Genetics & the Environment • Ex.) genes may affect a sunflower plant’s height & the color of its flowers • However, these conditions are also influenced by climate, soil conditions, & the availability of water • Ex.) Rabbit fur color in winter & summer

  32. Chromosome Number • All cells of an organism (except for sex cells, gametes) have the same # of chromosomes • Each body cell has 2 sets of chromosomes • Homologous chromosomes - the same chromosomes, 1 set from each parent

  33. Homologous Chromosomes

  34. Chromosome Number • Diploid - (2n) - a cell that has both sets of homologous chromosomes • Haploid - (n) - a cell that has half the normal set of chromosomes, or 1 set (only sex cells are haploid)

  35. Phases of Meiosis • Meiosis - process of reduction division, where the # of chromosomes per cell is cut in 1/2, through the separation of homologous chromosomes in a diploid cell

  36. Phases of Meiosis • During meiosis 1, crossing-over may occur • Crossing-over - when chromosomes exchange portions of their chromatids

  37. Phases of Meiosis • Crossing-over results in the exchange of alleles between homologous chromosomes & produces new combinations of alleles • Crossing-over increases genetic variation (genetic diversity, helps create genetically different organisms)

  38. Phases of Meiosis • Meiosis II, begins with 2 genetically different haploid (n) cells, & results in 4 (n) genetically different haploid cells • Therefore, Meiosis II is a mitotic division

  39. Meiosis I

  40. Meiosis II

  41. Gamete Formation • In males, the haploid gametes are sperm • In females, the haploid gametes are eggs

  42. Comparing Mitosis & Meiosis • Mitosis results in the production of 2 genetically identical diploid (2n) cells • Mitosis produces all cells of the body, except sex cells • Meiosis produces 4 (n) genetically different haploid cells • Meiosis produces ONLY sex cells (gametes)

  43. Gene Linkage • Each chromosome is a group of linked genes • It is the chromosomes, however, that line up independently, not individual genes (Principle of Independent Assortment)

More Related