ANTH 1013 1st Edition Lecture 4 Outline of Last Lecture I. Charles Darwin and the voyage of the HMS BeagleII. Alfred Russel Wallace (1823-1913)III. Origin of Species – DarwinIV. Natural SelectionV. Artificial SelectionVI. Theories of HeritabilityVII. Johan Gregor Mendel (1822-1884)Outline of Current Lecture I. Mendel’s Law of Independent AssortmentII. Examples of Medelian InheritanceIII. Mendelian Inheritance Lost and RediscoveredIV. GenesV. Cell Biology Related to Mendel’s TheoriesVI. Meiosis Big PictureCurrent LectureI. Mendel’s Law of Independent Assortmenti. Definition: each trait sorts independentlya. Alleles of one gene do not influence what happens with alleles from other genesThese 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.b. Must use FOIL when placing the Genotypes on the outside of the square (first, outside, inside, lastc. Standard ratio: AP = 9, Ap = 3, aP = 3, ap = 1d. If an individual that is homozygous dominant for a specific gene mates with an individual that is heterozygous for that gene, the frequency of the heterozygotes among the offspring will be: 50%II. Examples of Mendelian Inheritancei. Not all features follow these patterns of Mendelian Inheritance. In fact, MOST don’t.a. Albinism (albino) – recessive gene, Brachydactyly (club thumb) – dominant gene, Achondroplastic dwarfism – dominant geneii. ABO blood typinga. Type A = AA or AOb. Type B = BB or BOc. Type O = OOd. Type AB = ABIII. Mendelian Inheritance Lost and Rediscoveredi. Mendel’s work published in 1866a. Work only cited three times over the following 35 years (ignored)b. Published just after Origin of Species, but Darwin was unaware of workii. Results confirmed in other pea plants, but not generalizable to other organismsa. Pea research discontinued in 1864 after weevil infestationb. All research abandoned in 1871 after Mendel is elected abbot of the monasteryc. Mendel dies in 1884 from nephritisiii. Mendel’s work was rediscovered in 1900 after independent confirmation of his work by Hugo de Vries, Carl Correns, and Enrich von Tschermaka. Integration of Mendel’s and Darwin’s that occurred in the early 20th century is now referred to as the Modern Evolutionary SynthesisIV. Genesi. Work by cytologists (cell biologists) in the late 1880’s led to identification of different types of cells and microscopic structure inside cellsii. Types of cells: a. Prokaryoticb. Eukaryoticiii. Prokaryotic Cellsa. Primitive cell type – unicellular orginismsb. Characteristic of bacteriac. No nucleusd. DNA is circulariv. Eukaryotic Cellsa. Contains nucleus and organellesb. Found in multicellular organisms – animals, plants, fungi, and protistsc. Originated over 1.6 billion years agod. DNA organized into chromosomese. Mitochondria1. Organelle inside a eukaryotic cell2. Cellular power plants – generate most of the cells energy3. Contains separate type of DNA, mitochondrial DNA (mtDNA) that iscircular in formv. What is a chromosome?a. We can see chromosomes in humans1. Humans have 23 pairs of chromosomesa. 22 autosome pairsb. 1 “sex chromosome” pair2. Chimps and gorillas have one more chromosome than humansvi. Somatic cells vs. Gametesa. All cells in body contains chromosomes1. But, number of chromosomes varies depending on whether cels are somatic and gameticb. Somatic cells – all cells except gametes1. 46 chromosomes (23 pairs) = diploid2. Undergo mitosis (divide to create 2 identical daughter cells)3. Stages of mitosis:a. Interphase – cell replication occurs, chromosomes not visibleb. Prophase – nuclear membrane disappears, double-strandedchromosomes are visiblec. Metaphase – chromosomes aligned at center of cell d. Anaphase – chromosomes split at centromere, strands separate and move to opposite ends of celle. Telophase – cell membrane pinches as cell continues to divide, chromosomes begin to uncoilf. Cytokinesis – cytoplasm is divided, 2 identical daughter cellspresent, no chromosomes visiblec. Gametes – cells that join during fertilization1. 23 chromosomes (no pairs) = haploid2. Undergo meiosisa. Meiosis results in four daughter cells that have half the number of chromosomes as the original parent cellb. Like mitosis, starts with a diploid parent cell then duplicatesthe DNAc. Unlike mitosis, goes through 2 rounds of cell division producing 4 daughter cells3. Stages of meiosisa. Interphase – cell replication occurs, chromosomes not visibleb. Prophase I – nuclear envelope disappears, double-stranded chromosomes become visible, CROSSING-OVER OCCURSc. Metaphase I – homologous chromosome pairs migrate to the center of celld. Anaphase I – homologous pairs of chromosomes separate and move to opposite ends of the celle. Telophase I – cell membrane pinches as cell continues to divide, nuclear envelope reformsf. Cytokinesis – two haploid daughter cells present, cytoplasmin process of dividingg. Prophase II – chromosomes with 2 chromatids become visibleh. Metaphase II – chromosomes with 2 chromatids line up at the equator of the celli. Anaphase II – Chromosomes split so that a chromosome with only one chromatid moves toward each pole of the cellj. Telophase II – chromosomes with only one chromatid get surrounded by nuclear envelopesk. Final result = 4 haploid cells4. Crossing overa. Process by which novel combinations of genes are createdi. Exchange of genetic material between paired chromosomes during meiosis (does not happen duringmitosis!)b. Occurs during prophase Ic. Also known as recombination5. Sex cells – sperm and eggd. Mitosis vs. MeiosisV. Cell Biology related to Mendel’s theoriesi. The separation of homologous chromosomes during meiosis 1 is the process behind Mendel’s Law of Segregationii. You can’t predict which members of different chromosome pairs will move together through meiosis is Mendel’s law of independent assortmentiii. Exceptions to independent assortmenta. Genes are sorted into gametes independently of one anotherb. Now known to be true only for genes on separate chromosomesc. Genes on the same chromosome are LINKED, they do not assort independentlyVI. Meiosis Big Picturei. Meiosis shuffles genetic variationa. For humans, with 23 pairs of chromosomes, there are 2^23 = 8,388,608 possible haploid cell types without crossing overii. Things can go wrong during meiosisa. Non-disjunction – trisomy 21 (down syndrome)b.