Anthropology 270 Week 2 Notes
Anthropology 270 Week 2 Notes ANTH 270
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This 7 page Class Notes was uploaded by Aliya Cook on Thursday April 7, 2016. The Class Notes belongs to ANTH 270 at University of Oregon taught by Nelson Ting in Spring 2016. Since its upload, it has received 4 views. For similar materials see Intro Biological Anth >3 in anthropology, evolution, sphr at University of Oregon.
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Date Created: 04/07/16
Aliya Cook ANTH 270 04/04/2016 Biological Anthropology: Week 2 Notes Genetics and Inheritance Last Lecture: PreDarwinian world view impeded the development of evolutionary thinking Darwin developed the theory of natural selection and was influence by people before him Theory of Natural Selection Differential reproduction—individuals with favorable genes produce more offspring Limited resources lead to competition Individuals show variation Some variants have a selective advantage over others due to environmental factors These variants reproduce more than other individuals thus passing on a greater proportion of their genes Genetics—The Big Picture Darwin could not explain everything: i. How traits were inherited ii. How variation originates and how it’s maintained Genetics later provides us with this information Next two lectures focus on: i. How info is passed from one generation to the next ii. How genetic info creates proteins iii. Why variation exists iv. Why the distribution of genetic variation might change over time in a population Evolution was redefined to not only include natural selection, but other genetic mechanisms as well How are traits passed from one generation to the next? What molecular mechanism underlies patterns of inheritance? Why does variation exist and how is it maintained? 1 Century Heredity Concepts Lamarckian: offspring inherited traits from parents acquired in life Blending: parental traits/genes mixed to produce intermediate offspring Gregor Mendel (18221884), Mendel’s Pea Garden i. Breeding pea plants ii. Published results in 1865, not paid much attention to, didn’t really see much attention until he died, twenty years later, not rediscovered until the 1900’s iii. Only paper he ever published iv. Take pure strains of pea plants that had certain traits and breed them to see what the traits were in the next generations and he would count them v. Began with pure strains vi. Applied statistical properties vii. Used distinct traits with two contrasts Height of the plant (tall v. short) Color of the seed (yellow v. green In his method he slowly discovered the idea of recessive v. dominant traits By crossing tall plants with short plants his first generation would be solely tall, but then breeding them with themselves he noticed that the short plants appeared once more Mendel’s First Law: Principle of Segregation Traits are controlled by discrete units (genes) These units occur in pairs (alleles) Offspring inherit one unit from each parent Mendel realized that the units for absent characters in the first generation were not gone but were still present (e.g. recessive) For a recessive trait to be expressed an individual must have two copies (homozygous) For a dominant trait to be expressed an individual only needs one copy (heterozygous) Whatever alleles you have are called the genotype, then whatever expressed or seen traits are called the phenotype. T(0.5) T(0.5 ) t(0.5 Tt Tt ) t(.5) Tt Tt Mendel’s Second Law: Principle of Independent Assortment Applies to two or more traits i. The hereditary units that code for traits assort independently of each other ii. The inheritance pattern of one trait does not affect the inheritance pattern of another trait Human Cells Eukaryote: any cell that contains a nucleus in its cells In the nucleus is a copy of your genome: a copy of your complete DNA Every cell in your body has a copy of your genome, but not every cell has each thing turned on, so that’s why they all look different Deoxyribonucleic Acid (DNA) Francis Crick and James Watson The Structure of DNA i. Doublestranded helix composed of two complementary strands ii. Each strand is composed of a linear sequence of nucleotides with a sugar phosphate backbone iii. The two strands are connected by hydrogen bonds formed between complementary nucleotides (bases) Nucleotides i. Adenine goes to Thymine ii. Thymine goes to Adenine iii. Guanine goes to Cytosine iv. Cytosine goes to Guanine DNA Replication i. Two strands of the DNA molecule are separated ii. Each strand serves as a template for a new strand iii. While separated, unattached nucleotides are attracted to the free ends of attached nucleotides iv. A new strand is formed and replication is complete Chromosomes Discrete structures composed of DNA and protein How DNA is organized during cell division Locust is the physical position of where the genes or alleles occur Chromosomal Complement i. In most human cells there are two copies of each chromosome ii. In humans, the total count of chromosomes per cell is 46 (23 pairs) iii. That is, 22 autosomal pairs and 1 sex chromosome pair Primate chromosomes very similar to human Mitosis and Meiosis Mitosis is cell division in somatic cells i. End with two daughter cells that are exact copies of one another ii. One round of division iii. Daughter cells end with 46 chromosomes Meiosis is cell division in gametes/sex cells i. Two rounds of cell division ii. End with four daughter cells iii. Each daughter cell ends with 23 singlestrand chromosomes iv. These are sperm and ova Cancer—errors from mitosis Down syndrome—errors from meiosis Recombination Occurs when homologous chromosomes exchange chunks during the meiosis This results in different linkages between genes in the gametes Cells will never result in the exact same combination of genes What is a gene? A sequence of DNA bases that codes for a protein Protein ex: Hemoglobin i. Protein found in red blood cells that bings oxygen and allows transport to cells throughout the body Protein Synthesis DNA directs the creation of proteins Proteins are composed of chains of amino acids, which are determined by DNA sequence Proteins are made in the cytoplasm of the cell The Central Dogma of Molecular Biology A gene is transcribed into RNA which is translated into a protein DNA v. RNA DNA is double stranded while RNA is single stranded DNA has a thymine, RNA has uracil DNA has deoxyribose sugar while RNA has ribose Amino Acids Molecules which are the building blocks of all proteins. There are 20 distinct amino acids Also known as polypeptide chains Genetic Code There is a code to translate mRNA sequences into proteins Influence of Genes on Traits Mendelian Traits ii. Controlled by alleles at only one genetic locus iii. Also called discrete or discontinuous traits iv. Ex: blood type, genetic disorders such as SickleCell Anemia and TaySachs disease Single gene effect: each gene has a distinct effect Polygenic trait: several genes contribute to a single effect Pleiotropy: a single gene has multiple effects Take Home Points Mendel outlines the basic principles of inheritance in his pea plant ex The structure of DNA allows for the replication and transmission of traits from one generation to the next Processes that occur during meiosis and sexual reproduction allow for increased biological variation Genes encode for traits via the central dogma is molecular biology Why the distribution of genetic variation might change over time in a population? Modern (NeoDarwinian) Synthesis Sewall Wright Rediscovery of Mendelian Genetics (1900s) Before the rediscovery people believed much of the old ideas, such as blending, and Lamarckian thinking Emphasis on natural selection and mutation modified and expanded (1930s) Resistance to natural selection mostly until the 1930s New generation of geneticists came along to explain more thoroughly R. Fisher, J.B.S. Haldane, S. Wright, T. Dobzhansky, G.G. Simpson, E. Mayr The naturalists for a long time did not know how genetics worked Geneticists and naturalists were working parallel to one another but not understanding one another at all Evolution—A Modern Definition Microevolution: a change in allele frequency in a population over time Allele frequency: the percentage of all the alleles at a locus accounted for by one specific allele in a population Population: a community of interbreeding individuals Macroevolution: Large scale complex evolutionary change in whole systems over a long period of time—speciation Evolutionary Forces (Processes) Force that creates a new variation 1. Mutation Change in DNA, may result in a change in the phenotype of an organism Creates variation on which other forces can act Mutation is the creative force in evolution, as it is the only force that can produce novel variation Forces that reshuffle existing variation 1. Natural selection Changes in frequencies of certain traits in pop. due to differential reproductive success Based on selective pressures in specific environments Alleles associated with traits that allow for better survival and/or reproduction increase in frequency in the next generation 2. Genetic drift Fluctuations in a gene pool due to random factors, typically as a result of small pop. size Evolution due to small population size Two common types of genetic drift: Population Bottleneck—drastic reduction in population size; Founder Effect—small population branches off that is not representative of the larger population 3. Gene flow Evolution in populations through the exchange of genes from other populations Mutation: Introducing Variation An alteration in DNA, which may or may not affect cellular function Can introduce new variation into a pop. Selection: Redistributing Variation Molecular Genetics and Anthropology What can genetics tell us about human (and primate) demography? 1) Past Migrations, bottlenecks, social behavior What are the genetic underpinnings of human (and primate) phenotypic traits? 2) Adaptation, geneculture, coevolution, human distinctiveness, diseaseresistance How are primates related to one another? 3) Phylogeny, classification, evolutionary history What can genetics tell us about individual identity? 4) Forensics Types of Evolution Microevolution Macroevolution Macroevolution—Fundamental Questions How do we define species? 1. Species are often difficult to define because of the existence of different species concepts 2. A species is an interbreeding group of animals or plants that are reproductively isolated from other such groups (Biological Species Concept) What is speciation? 1. Process by which a new species evolves from an earlier (ancestral) one 2. Can occur by Cladogenesis (branching, a population branches into others) and Anagenesis (nonbranching, dramatic changes in one population) 3. Adaptive Radiation: the relatively rapid expansion and diversification of an evolving group of organisms as they adapt to new niches What causes speciation and maintains species boundaries? 1. Lack of gene flow maintains species boundaries 2. Isolation and interruption of gene flow cause speciation, followed by micro evolutionary change Common speciation mechanism: Allopatric Speciation
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