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Chapter 3 ISS 220 notes

by: Anne Koster

Chapter 3 ISS 220 notes ISS 220

Marketplace > Michigan State University > ISS 220 > Chapter 3 ISS 220 notes
Anne Koster
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J. Hefner

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J Hefner.
J. Hefner
Class Notes
ISS 220, J. Hefner
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This 5 page Class Notes was uploaded by Anne Koster on Monday January 25, 2016. The Class Notes belongs to ISS 220 at Michigan State University taught by J. Hefner in Fall 2015. Since its upload, it has received 175 views.


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Date Created: 01/25/16
ISS 220 J hefner 10 11 Chapter 3 Gregory Mendel a monk that crossed different strains of purebred plants and studied their progeny His work illustrates the basic rules of inheritance Mendel s principle of Independent assortment The distribution of one pair of alleles into gametes does not influence the distribution of another pair The genes controlling different traits are inherited independently of one another a Today we know that this happens because the genes that control plant height and seed color are located on different chromosomes and during meiosis the chromosomes travel to newly forming cells indecently of another Mendelian Traits discrete traits or traits of simple inheritance Characteristics that are influences by alleles at only one genetic locus Antigens Large molecules found on the surface of cells Several different loci governing antigens on red and white blood cells are known Codominance The expression of both alleles in heterozygotes IN this situation neither allele is dominant or recessive both influence the phenotype Hybrids Off spring of parents that differ from each other with regard to certain aspects of genetic makeup heterozygotes Genetics The study of gene structure and action and the pattern of transmission of traits form parent to offspring a Genetic mechanisms are the foundation for evolutionary change Cells basic units of life in all living things to understand evolution and genetics we must understand that the cells in some cases are singular and in others complex multicellular forms there are billions of cells that make up things like birds or mammals a Cells of all living organisms share many similarities because they share a common evolutionary history b Before a cell divides its DNA must replicate Life on earth can be tracked back 37 billion years to prokaryotic cells which are single celled organisms that today are represented by bacteria and bluegreen algae More complex cells appeared 12 billion years ago these are Eukaryotic cells a These cells are found in all multicellular organisms Eukaryotic cell is a three dimensional structure that contains a variety of structures called organelles that are enclosed within a cell membrane a One of these organelles is the nucleus the nucleus contains two acids that contain the genetic information to control the cells functions DNA and RNA 12 Somatic cells all the cells in the body expect those involved in reproduction 13 Gametes Reproductive cells eggs and sperm in animals developed from precursor cells in ovaries and testes a The sole function of a sex cell is to unite with a gamete from another individual to form a zygote 14 Zygote a cell formed by the union of an egg and a sperm cell It contains the full complement of chromosomes and has potential to develop an entire organism 15 DNA molecule is composed of two chains of even smaller molecules called nucleotides a Nucleotides are the basic units of DNA molecules composed of sugar a phosphate unit and one of four DNA bases 16 Principle of segregation Discrete units or genes occur in pairs because the chromosomes occur in pairs a During gamete production members of each gene pair separate so each gamete contains one member of a pair b During fertilization the full number of chromosomes is restored and members of a gene or allele pairs are reunited 17 Dominance dominant traits are governed by an allele that can be expressed in the presence of another different allele a Dominant alleles prevent the expression of recessive alleles in heterozygotes b Thus phenotypically individuals that are homozygote dominant two dominant alleles appear identical to heterozygotes one dominant allele one recessive allele c Common misconception is that dominant alleles are better stronger or more common in population but this is not true 18 Recessive traits are not expressed in heterozygotes a Must receive allele to be expressed there must be two copies of the allele b Commonly associated with lack of a substance usually an enzyme 19 Homozygous Vs Heterozygous a Homozygous have the same allele at the same locus on both members of a pair of chromosomes b Heterozygous have different alleles at the same locus on member of a pair of chromosomes 20 Locus The position on a chromosome where a given gene occurs 21 22 23 24 25 26 27 28 a Sometimes used interchangeably with gene but this is incorrect Polygenic traits that are influences by genes at two or more loci a Ex Skin color stature eye color b Since these traits can generally be measured in some way anthropologists treat them statistically by using simple summary stats such as mean average or standard deviation a measurement of variation within a group c Many polygenic traits are influences by environmental factors Polygenic Inheritance polygenic traits or continuous traits are governed by alleles of two or more loci and each locus has some influence on the phenotype Skin color determined by pigment production by specialized cells called melanocytes a Melanin production is influenced by interaction between several different loci that until recently had not been identified Alleles are alternate forms of a genes that occur at the same locus on a pair of chromosomes and influence the same trait Genotype is the underlying genetic makeup of an individual Can refer to the organisms entire genetic makeup of to the alleles at the particular locus a sets limit and potentials for development but it also interacts with the environment and this genetic environmental interaction influences many aspects of the phenotypes Phenotype is the observable or detectable physical characteristics of an organism The detectable expressions of a genotype frequently influenced by environment Independent assortment the distribution of one pair of alleles into gametes does not influence the distribution of another pair a Genes controlling different traits are inherited independently of one another b This results in a lot of variation Punnett Square demonstrates how alleles can be combined when the F1 plants are self fertilized to produce and F2 generation pollen oquot B b 63 B BB Bb pistil 9 b Q Bb bb 29 30 31 32 33 34 35 36 37 38 Random assortment the chance distribution of chromosomes to daughter cells during meiosis along with recombination but not new alleles from meiosis Mitochondrial inheritance All cells contain mitochondria that convert energy into a form that can be used by the cell Each mitochondrion contains copies of a ringshaped DNA molecule or chromosome a Animals of both sexes inherit their mtDNA and all mitochondrial traits from their mothers b All variation is caused by mutation Evolution is a two stage process a Production and redistribution of Variation b Natural selection acting on Variation whereby differences among individuals affect their ability to reproduce Evolution s current definition a change in allele frequency from one generation to the next a Allele frequencies are indicators of the genetic makeup of a population the members of which share a common gene pool b In a population allele frequencies refer to the percentage of all the alleles at a locus accounted for by one specific allele these are indicators of the genetic makeup of a population Microevolution small genetic changes that occur within a species a The short term effects Macroevolution large scale changes that occur in population after many generations such as appearance Factors that produce and redistribute variation a Mutation b Gene flow c Genetic drift and founder effect d Recombination Gene Flow the exchange of genes between populations a If individuals move temporarily and mate n a new population and they don t necessarily stay there Genetic Drift occurs solely because the population is small a Alleles with low frequencies may not be passed to offspring and eventually disappear from the population Founder Effect occurs when a small band of founders leaves it s parent group and forms a colony elsewhere a A new population is established and all members within that population are descendants of the founders b A once rare allele that was carried by one of the founders can eventually became common 39 Mutation molecular alteration in genetic material a 9906 If one allele changes to another the gene itself is altered then is it mutation For mutation to have evaluation significance it must occur in a gamete Rates are generally low Only way to produce NEW genes When combined with natural selection evolutionary changes can occur and can occur more rapidly 40 Directional Change in allele frequency means that natural selection can increase or decrease the frequency of certain alleles over time in ways that are beneficial in specific environmental settings 41 Recombination doesn t change allele frequencies or cause evolution but it does change the composition of parts of chromosomes a Affects how some genes act and slight changes of gene function can become material for natural selection to act upon 42 Natural selection provides directional changes in allele frequency relative to specific environmental factors a If the environment changes selection pressures also change b If there are long term environmental changes in a consistent direction then the allele frequencies should also gradually shift each generation Chapter Questions How can the same process od genetic inheritance produce these different phenotypic conditions How does the environment shape the expression of Mendelian and polygenic traits How did Mendel use the term dominant What is the principle of segregation When alleles are introduced into a population from a new population this is known as


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