Chapter 14 notes
Chapter 14 notes BIOl 1020-003
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This 4 page Class Notes was uploaded by Crystal Boutwell on Saturday October 31, 2015. The Class Notes belongs to BIOl 1020-003 at Auburn University taught by Dr. Zhong in Fall 2015. Since its upload, it has received 23 views. For similar materials see Principles of Biology in Biology at Auburn University.
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Date Created: 10/31/15
II CHAPTER 142 MENDEL AND THE GENE IDEA Compiled by Crystal Boutwell Introduction A Blending hypothesis i In the 1800s this theorized that the traits a mother and father possessed would be blended into their offspring like when you blend paint colors together ii The problem After enough mixing you get one uniform color and our population is nowhere near being uniform yet B Gene Idea That parent s pass on heritable traits called genes i This is more like a deck of cards that can shuf ed and passed out ii Proposed by Gregor Mendel an Austrian Monk who experimented in a garden with pea plants Laws of Inheritance and genetic vocab A Character the noun used to describe each inheritable trait or feature Ex hair color eye color jaw line etc B Trait each variant for the character brown hair is a trait 0 Truebreeding when after many generations of selfpollinating an organisms produces the same variety as the parent plant AA or bb Hybridization when you cross two different truebreeding parents AA X aa P generation parental generation F1 generation first generation of offspring mama F2 generation second hybrid offspringfrom the F1 i Mendel analyzed F2 plants to make his hypotheses F The Law of Segregation states that genes have alternate forms or alleles which separate during meiosis and gamete formation so that each egg or sperm only carries one form of the gene This explains the 31 ratio of f2 phenotypes Each organism inherits one allele for each gene from each parent i Heterozygotes the genes are different One is dominant and one is recessive l The dominant allele determines the appearance of the organism 2 The recessive allele typically has no visible effect on the organism ii Homozygous the genes are the same both dominant or both recessive I Allele the alternative versions brown or black or red or blonde hair i Alleles are simply different orders of nucleotides in DNA J Punnet Square a diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup III IV K Genotype the genetic makeup of an organism Pp or KK or rr L Phenotype The physical appearance or observable traits of an organism The phenotype of two organisms can be the same even if their genotypes are not M Testcross When an organism with an unknown genotype is crossed with a recessive homozygous organism to determine it s genotype N The Law of Independent Assortment the two alleles for a gene separate independently of alleles for any different alleles For example the alleles that determine hair color disperse independently of the alleles that determine height 0 Monohybrid progeny of truebreeders for ONE character Aa P Dihybrid progeny of truebreeders for TWO characters AaBb Probability Laws and Mendelian Inheritance A Scale i 0 an event is certain to not happen ii 1 an event is certain to happen iii Probabilities of all possible outcomes must add up to one B Multiplication rule the probability of two or more events happening at the same time is equal to the product of the individual probabilities of the independent single events i If the probability that a kid will be born with brown hair is IA and the probability that a kid will be born with blue eyes is 12 then the probability that a kid will be born with brown hair and blue eyes is 14 times 12 or 18 C Addition rule the probability that any one of two or more mutually exclusive events will occur is calculated by adding their individual probabilities i Used for heterozygotes Degrees of dominance A Single Gene i Complete dominance the heterozygous phenotype is the same as that of homozygous dominant Rr looks the same as RR ii Incomplete dominance the homozygous dominant phenotype is not the same as the heterozygous phenotype R red owers r white owers RR red rrwhite Rr pink iii Codominance both phenotypes are expressed AB blood type iv Multiple alleles some genes have more than two alleles like blood type v Pleiotropy one gene will affect multiple phenotypic characters SickleCell disease B Two or more genes i Epistasis when the phenotypic expression of one gene affects the expression of another gene 1 Ex in labs Black fur B is dominant to brown fur b Expression of pigmentation E is dominant to not expressing pigmentation e If ee occurs the dog will have no pigmentation despite the code for fur color So BBee creates a yellow lab ii Polygenic inheritance a single phenotypic character is affected by two or more genes 1 Quantitative characters human skin color and height are examples Have many different possibilities compared to wrinkled or rounded peas 7 iii Our environment also has an impact on our phenotypes V Mendalian Patterns of Inheritance A Pedigree a genetic family tree 391 i Helps us calculate the probability that a future child will have a particular genotype and phenotype B Recessive alleles must be homozygous in order KEY to be eXpressed i Heterozygous are considered carriers A C Male Female MEquot Female common lethal genetic disease Cystic Fibrosis most i Chloride transport channels defective or absent in plasma membranes ii Can cause death by age of 5 D Sickle Cell disease common in people of African descent i Caused by substitution of a single amino acid in hemoglobin ii Recessive homozygous needed for full effects but Rr can effect the phenotype 1 Organismal level R is incompletely dominant to r 2 Molecular level R and r are codominant iii Evolution having a single copy of sickle cell allele reduces the severity of malaria attacks E Dominant disorders i Achondroplasia dwarfism 9999 of people are homozygous recessive ii Huntignton s disease lethal iii Just because an allele is dominant does not mean it is common F Fetal Testing i Amniocentesis done between 14th and 16th week of pregnancy 1 Uses amniotic uid ii Chorionic Villus sampling CVS 1 Done between the 8th and tenth week 2 A sample of tissue from the placenta iii Newborn screening now very common and mandatory in some places
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