BIOB 272 1st Edition Lecture 7 Outline of Last Lecture Mendelian Genetics ContinuedI. Mendel’s Principles1. Dominance2. Segregation3. Independent AssortmentII. Mendel’s Experimental approachIII. Example of Independent Assortment IV. Clicker QuestionsV. Mendelian laws of segregationVI. Why is independent assortment important?Outline of Current Lecture Meiosis, Sex DeterminationI. What is sex? (in a genetic sense)II. Asexual Reproduction in bacteriaIII. Bacteria acquire new DNA three main waysIV. Genetic Transmission in Diploid, Sexual, Eukaryotesa. Cycleb. Genomes (in humans):c. Chromosomes V. Mitosis VI. Meiosis (germinal cell division):These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.VII. Sex Determination- Animal Male/Female Sexes Determined bya. Environmental Factorsb. Chromosomal Factorsi. XY (mammals, Drosophila)ii. ZW (butterflies, birds)iii. XO (some insects)iv. Haplodiploidy (bees, ants, etc.) c. Anisogamy d. Plants ReproductionVIII. Clicker QuestionCurrent LectureMeiosis, Sex DeterminationI. What is sex? (in a genetic sense)a. Creation of new genetic combinations(genetic recombination)b. Genetic recombination (broadly, sex) isuniversal:i. Virusesii. Prokaryotes (bacteria, etc.)iii. EukaryotesII. Asexual Reproduction in bacteria:-doubles its genetic materialMother Cell with bacterial chromosome => chromosome splits in half with septum between => two daughter cells III. Bacteria acquire new DNA three main ways:1. Conjugation involves acquisition of DNA directlyfrom another bacterium.2. Transformation involves acquisition of DNA fromthe environment.3. Transduction involves acquisition of bacterial DNA via a bacteriophage intermediate.**KEY POINT: Bacteria (and other non-eukaryotes) are mostly asexual, but do have opportunities forgenetic exchange which may be very importantevolutionarily.IV. Genetic Transmission in Diploid, Sexual, Eukaryotesd. Cycle :Meiosis=>Gametes(1N) => Fertilization (egg and sperm) => Zygote (2N)=> Mitosis (cell division and growth)=>Mature Adult (2N) => Repeat Cyclee. Genomes (in humans):a. Large genomesb. 46 chromosomes (23 pairs)c. 3 billion nucleotides= about 2 meters of DNAf. Chromosomes:a. Centromere combines sister chromatids-Sister chromatids have replicated copies of the samealleles of a given geneb. Homologous chromosomes: 1 from mom, 1 from dada. Carry the same genes, butmay have different versions or alleles of a given geneV. Mitosis:c. 1 duplication ofchromosomes,1 divisiond. 1 diploid cell =>2 diploid cells(all identical)e. occurs insomatic cells =>growthf. Homologous chromosomes do not pairVI. Meiosis (germinal cell division):g. 1 duplication ofchromosomes, 2divisionsh. 1 diploid cell =>4 haploid cells(each unique)i. occurs in germline (specializedcells)j. homologous chromosomes pair (synapsis), cross over, and then separatek. New genetic combinations are produced byindependent assortment through:- Random segregation of chromosomes- Crossing-over between pairs of homologous chromosomes- Chromosomal basis of Mendel’s principles-During metaphase I, the bivalents can align themselves in two different ways -Independent assortment of the R/r and Y/y alleles**Meiosis: Key points:- 1 duplication, 2 divisions- 1 diploid (2N) cell => 4 haploid (1N) cells- Each haploid gamete is a unique remix of theparental genotype- independent assortment of chromosomes- crossing over between homologues- Diploidy (2N) is restored by fusion of haploidgametes (i.e., fertilization of egg by sperm)VII. Sex Determination- Many organisms have 2 mating types or sexes (usually, but not always, male and female)- Animal Male/Female Sexes Determined by:c. Environmental Factorsi. Many reptiles-i.e. turtles- sex (male vs. female) determined by temperatured. Chromosomal Factorsi. XY (mammals, Drosophila)- X and Y chromosomes pair during meisosis- They pair at the homologous (pseudoautosomal) region= very small region- Males are the heterogametic sex- For X-linked diseases or for family balancing. Using flow cytomettry, X or- Y-bearing sperm can be enriched. MicroSort technology provides anaverage increase in X-bearing sperm to 88% and Y-bearing sperm to 73%.- High Variance- 10 sex chromosomes:o Males - X1Y1 X2Y2 X3Y3 X4Y4 X5Y5o Females - X1X1 X2X2 X3X3 X4X4 X5X5ii. ZW (butterflies, birds)- Presence or absence of W determines sex- Sex determination in all birds,- butterflies, moths, and some other species- female= ZW , male= ZZiii. XO (some insects)iv. Haplodiploidy (bees, ants, etc.)- 15% of all animal species use= works well- found in all Hymenoptera (bees, wasps, ants)- female= 32 diploid, male=16 haploid- Males are clones of queen’s gametes, femaleshave dads-1N egg=> mitosis=> haploid MM-1N egg=> fertilization=> diploid FFc. Anisogamy: Sexual reproduction involving the fusion of two dissimilar gametes.Larger gametes are defined as female. Smaller gametes are defined as maled. Plants Reproduction: - More than 90% of all plants are hermaphrodites (male and female in same individual)!!! Less than 10% of all plants have separate sexes. Hermaphrodites are very rare in animals.VIII. Clicker Question:Is self-fertilization a form of asexual or sexualreproduction?(a) Asexual (b) SexualAnswer: b.