1 / 60

Chapter 11 : Genetics

Chapter 11 : Genetics. 11.1 The Work of Gregor Mendel. Genetics: study of Heredity , or the passing of characteristics from parents to offspring . Traits : Inherited characteristics . Examples: eye color, red hair , height …. http://www.writing.ucsb.edu/faculty/samuels/dna.jpg.

lharvey
Download Presentation

Chapter 11 : 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. Chapter 11: Genetics

  2. 11.1 The Work of Gregor Mendel • Genetics: study of Heredity, or the passing of characteristics from parents to offspring. • Traits: Inherited characteristics. • Examples: eye color, red hair, height …. http://www.writing.ucsb.edu/faculty/samuels/dna.jpg

  3. Gametes: The sex cells found in an individual or plant - egg or sperm and plants pollen . • Fertilization: The uniting of male and female gametes.

  4. Mendel’s Peas • Gregor Mendel (1822-1884): An Austrian monk. He wanted to know how traits were passed from parent to child. Studied pea plants.

  5. Mendel started out with plants that he knew would only produce tall and pea plants that only produces short offspring. • He mated short plants with tall plants. • All the offspring were tall http://www.mhhe.com/biosci/esp/2001_gbio/folder_structure/ge/m2/s2/assets/images/gem2s2_1.jpg

  6. Tall Short Tall Tall Tall Tall Tall Short

  7. The parental generation:P1 generation • The first generation of offspring: F1 generation • The second generation of offspring: F2 generation http://www.fastplants.org/graphics/genetics/parent_F2.jpg

  8. Mendel had the new tall offspring (F1 plants) self-pollinate and observed the second generation (F2 Plants). • The resulting plants were tall ¾ of the time, and short ¼ of the time! http://www.biology.arizona.edu/mendelian_genetics/problem_sets/monohybrid_cross/graphics/02Q.gif

  9. What did Mendel concluded about trait inheritance? factors are passed from generation to generation. Genes: are the Factors that determine traits. Ex. Hair and eye color, height

  10. There are two alleles that determine trait inheritance. • Alleles: A particular form of a gene, one comes from the mother, one from the father. • Ex. Gene = height, the allele could be tall or short. • Gene = eye color, the allele could be light or dark. http://ghs.gresham.k12.or.us/science/ps/sci/soph/genetics/alleles.gif

  11. The Role of Dominance • If there are two alleles, and only one observed trait, which allele is dominant? • A dominant allele is alwaysexpressed. • A recessive allele not expressed when in the presence of a dominant allele. is expressed when paired with another recessive allele. http://wellspring.isinj.com/bio/principlesI/Images/segregation.jpg

  12. T is dominant to t which is recessive. Genotype is the genes. Phenotype is the physical appearance.

  13. T is dominant to t which is recessive. • TT = homozygous dominant • Tt = heterozygous • tt = homozygous recessive

  14. Law of SEGREGATION • Mendel’s first law. • Segregation=separation of two alleles during gamete formation during meiosis , each gamete receives one of the two alleles.

  15. Law of Independent Assortment Segregation + Independent assortment = four possible combinations of alleles. Law of Independent Assortment states traits like shape and seed color are inherited independently of each other.

  16. Each F1 has a tall and short allele (for the gene for height) that it can pass on to its offspring (F2)

  17. 11.2 Punnett Squares or Test Cross - A diagram used to show inheritance patterns in offspring • - Used to predict / compare variation in traits

  18. 11.3 Mendelian Genetics • Monohybridcross: comparing one gene. Each parent donates one allele to the offspring

  19. Homozygous: Two of the (same size allele) for a trait. • Ex. TT or tt. Purebreds • Heterozygous: Two different alleles for one trait. • Ex. Tt. • TT is homozygous dominant. • tt is homozygous recessive. • Tt is heterozygous.

  20. Dihybrid Cross (Two factor cross) • Ex. Wrinkled and yellow peas or round and green peas • Each parent donates two alleles to the offspring

  21. Phenotypes - Dihybrid Crosses RRYY, RRYy, RrYY, RrYy = Round Yellow rrYY, rrYy = Wrinkled Yellow RRyy, Rryy = Round Green rryy = Wrinkled Green

  22. Incomplete Dominance • The heterozygous form of 2 different dominant alleles for a trait. • Example: Cross red(RR) flower with awhite(WW) flower. The resulting RW flower is pink. • Blending Colors!

  23. Codominance • Both alleles are expressed equally. • B for black, W for white • BB black, BW white and black, WW white. • Ex: Roan Cows, chickens

  24. Multiple Alleles More than 2 alleles exist for any one gene or trait. • The result is various expressions of the gene. • Example: various hair color and blood types

  25. Only two alleles are found in an individual, but there can be many different alleles that exist in a population. • Ex Blood type A,B, or O are all alleles • AB=type, AO=Type A, BO= Type B OO = Type O • You can not have ABO blood type because you only inherit two alleles.

  26. Polygenic Inheritance • Polygenic Inheritance: The inheritance pattern of a trait that is controlled by more than one gene. • Genes may be on the same chromosome or different chromosomes. • Ex. Skin color, eye color, hair color • Very often, the more dominant alleles that are involved, the more the trait is expressed. • Ex. 1 dominant allele: light skin, 2: darker,4: very dark, etc.

  27. Sex Linked Traits • Humans have 22 pairs ofautosomes, or chromosome pairs that resemble one another. The 23rd pair of chromosomes are called the sex chromosomes. • Sex Linked Traits: Traits controlled by alleles that are found on the sex chromosomes, usually on the X chromosome. • Ex. Color blindness, hemophilia • Notation is XBXb or XBXB(female) and XBY or XbY (male) instead of BB, Bb or bb. • Can a man pass on a sex linked trait to his son?? Show work.

  28. Mitosis Review • Mitosis produces cells with exactly the same amount of chromosomes as the original cell. • If this was the only means of cell division, offspring would end up with twice as many chromosomes as the parents.

  29. Meiosis Important Terms • Haploid: cell with one of each kind of chromosome (n) • Organisms produce gametes that are haploid…eggand sperm • Diploid: cell with two of each kind of chromosome (2n) • Body cells of animals/plants have chromosomes that occur in pairs…one from each parent • How do organisms produce haploid gametes? • To produce haploid gametes, organisms under go meiosis

  30. Meiosis • Meiosis has 2 separate divisions…Meiosis I and Meiosis II • Meiosis I begins with a Diploid cell…2n • Meiosis II finishes with 4 Haploid cells (1n) • These 4 Haploid cells are Gametes (Egg or Sperm) • With Fertilization, Sperm has (23) chromosomes and Egg (23)..Haploid…come together to produce a Zygote with (46) chromosomes..Diploid • This pattern of reproduction that involves the combining (fusion) of haploid gametes is called Sexual Reproduction

  31. Meiosis QUESTIONS/EXAMPLES TITLE: Where do you find homologous chromosomes? • in Diploid Cells • Ex: • Homologous Chromosomes: Paired chromosomes, each with genes for the same traits. These exist in Diploid cells and are what determine how an individual looks. Mom’s chromosomes for hair color Dad’s chromosomes for hair color

  32. Phases of Meiosis

  33. What happens within the cell during Interphase of Meiosis? DNA is Replication

  34. Meiosis I

  35. Prophase I Crossing Over can occur Each pair of homologous chromosomes come together to form a four-part structure called a Tetrad

  36. Metaphase I homologus pairs In Meiosis, the Tetrad of homologous chromosomes lines up down the middle

  37. Anaphase I What gets separated during Anaphase I? Spindle fibers pull homologous chromosomes toward opposite ends of the cell Homologus pairs

  38. Telophase I Are the two cells identical? No, the cells have different sets of chromosomes! Cells begin to separate into two cells

  39. Meiosis I

  40. Meiosis II Meiosis II is identical to Mitosis

  41. Prophase II Nuclear Membrane breaks down, chromosomes condense. Chromosomes do not replicate during Prophase II of Meiosis.

  42. Metaphase II Chromosomes line up down the center of the cell

  43. Anaphase II Sister Chromatids separate towards opposite ends of each cell

  44. Telophase II A nuclear envelope forms around each set of chromosomes and cytokinesis occurs, producing four daughter cells. Produces 4 Haploid Cells that are genetically different How many and what type of cells are produced at the end of Telophase II?4 haploid cells!!

  45. Meiosis II

  46. Results in 2 genetically identical cells Cells are diploid Results in 4 genetically different cells Cells are haploid Mitosis vs. Meiosis

  47. Meiosis causes Genetic Variation • Meiosis “shuffles” chromosomes so that the offspring are not identical to the parents • Principle of Independent Assortment: genes for different traits segregate INDEPENDENTLY during meiosis, as long as they are on separate chromosomes.

  48. HOW do genes for different traits separate independently? Answer:By chromosomes lining up randomly during meiosis.

  49. Crossing Over – an exchange of genetic material between homologous chromosomes • Occurs randomly anywhere on the chromosomes

More Related