CH 4 textbook & Lecture Notes Mendelian Evolution
CH 4 textbook & Lecture Notes Mendelian Evolution APY 203
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This 3 page Class Notes was uploaded by Demaree Rios on Tuesday January 26, 2016. The Class Notes belongs to APY 203 at University of Miami taught by William Pestle in Spring 2016. Since its upload, it has received 26 views. For similar materials see Principles of Physical Anthropology in anthropology, evolution, sphr at University of Miami.
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Date Created: 01/26/16
CHAPTER 4 NOTES Heredity amp Evolution gt PreMendelian Theories O preformation I within reproductive cells there existed preformed version of the offspring and the womb was just the incubator like little photocopies I doesn t explain mixed resemblance of offspring nor variation 0 blending inheritance I both parents contribute to the characteristics of their offspring I again doesn t explain variation or novel traits I eventually offspring would all regress to the same mean average bc no mechanism for introducing new variation so how would species evolve gt BASIC DNA INFO O directs all cell activity 0 JAMES WATSON FRANCIS CRICK ROSALIND FRANKLIN MAURICE WILKINS O composed of 2 chains of nucleotides 0 nucleotide deoxyribose sugar mol phosphate group 1 of 4 nitrogenous bases I double helical structuresiderails of ladder made up of sugars and phosphates rungs made up of nitrogen bases I adenine guanine thymine cytosine AT pair or GC pair 0 stability and simplicity preserves genetic code 0 chromosomes I are tightly packed strands of DNA during cell replication I humans have 23 pairs of chrom I pairs because one comes from mom one comes from dad so 46 total 0 gene the actual units small sections of DNA I sequence of DNA bases that code for specific trait aa protein ampor functional product I may be composed of thousands of DNA bases 0 locus the positior locatio on a chrom where a given gene occurs 0 alleles alternate forms of a gene occur same locus on paired chrom so govern same trait but different expression gt Mendel s Genetic Principles 0 Gregor Mendel 18821884 0 studied hybridization of garden peas focused on expression of certain characteristics height texture coloring etc from generation to generation I began interbreeding pea plants F1 generation all yellow F2 generation 34 yellow this pattern was recurring in other traits I no evidence of blending O Principle of Segregation Chrom occur in pairs so genes alleles occur in pairs during gamete formation the the pairs separate so ea gamete has one member of ea pair meiosis O dominant dom allele is the one that is expressed in the F1 gen I may partially or completely prevent expression of rec alleles dom always expressed genotype indicated by uppercase letter O recessive not expressed in F1 but is expressed in F2 gen I individual needs to copies of rec allele for the trait to be expressed genotype indicated by lowercase letter O codominance mixture of both alleles eXpressed 0 genetic makeup what genetically an individual has inherited from parents 0 homozygous inherit same allele at same locus on both members of chromosome pair AA or aa 0 heterozygous inherit diff alleles at same locus members of chrom pair Aa genotypic ratio 121 phenotypic ratio 31 0 genotype an organism s underlying genetic makeup or organism s allele s at a particular locus I diff genotypes can produce diff phenotype and it is possible to produce same phenotype via diff genotypes O phenotype observable phys char s eXpressions of organism gt dominance recessiveness is not all or nothing situation eX recessive allele maybe not be readily visible phenotypically but may be biochemically observable gt dominant traits should not be thought of as betterstrongermore common gt Mendelian Inheritance in Humans 0 Independent Assortment some char aren t inherited together genes that code for diff traits separate independently during gamete formation 0 Random Assortment the randomchance distribution of chrom to daughter cells during meiosis this random recombination is important for genetic variation 0 Particulate Inheritance O MendelianDiscrete Traits I controlled by alleles at only one locus I he was able to see discrete variation bc phenotypic eXpression was under control of one gene I discontinuous as in phenotypic eXpressions don t overlap clearly defined categories eX blood type I many Mend traits are biochem but some are phenotypically eXpressed I eXpression not usually in uenced by traits O Traits can be traced out through pedigree charts that diagrams generations of parents and offspring to determine modes of inheritance I autosomal dominantgt traits governed by dom alleles on autosomes I autosomal recessivegt I Xlinked dominant I Xlinked recessive I ylinked I mitochondrial gt NonMendelian Inheritance O Polygenic Continuous Traits I unlike Mendelian these traits show variation eX height skin hair eye color I governed by alleles at 2 or more loci ea locus bears phenotypic in uence this also makes it harder to ID all the loci associated with a given trait I important to not only consider genes associated with traits but also DNA sequences that regulate them I eXpression may be in uenced by environment 0 Mitochondrial Inheritance I ea mitochondrion contains mtDNA which is functionally and structurally similar to chrom DNA I mtDNA only passed on from the mother thus no meiosis no recombination variation only comes from mutation O Pleiotropy I the action of a single gene in uences more than one trait gt Genetic and Environmental Factors 0 phenotypes are not solely products of genotypes genotypes set limits for development but also interact with environment eX nutrition which in turn can in uence phenotype too less likely for env to in uence Mendelian inheritance women with particularly higher degree morning sickness have healthier and bigger babies bc its better to reject potentially harmful substances sickle cell anemia the benefits outweigh the potential harm bc the sickle shape is a defense to maleria thus it has been selected for