Bisc 130 Kemege test 4
Bisc 130 Kemege test 4 Bisc 130
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This page Class Notes was uploaded by Victoria Kemp on Wednesday February 3, 2016. The Class Notes belongs to Bisc 130 at Louisiana Tech University taught by Dr. Kyle Kemege in Fall 2015. Since its upload, it has received 172 views. For similar materials see Introduction to Biology in Natural Sciences and Mathematics at Louisiana Tech University.
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Date Created: 02/03/16
Alternate forms of a gene Genesproteins Proteins lead to physical Characteristics total set of alleles that an individual has the appearancephysical characteristics of an individual 0 Result of the genotype We have 2 sets of chromosomes 0 Two alleles for each gene 0 But only one phenotype Pea Plants REPRODUCTION each ower has female sex organs ovaries that house the eggs and male sex organsanthers make pollen contains sperm pollen from a ower can fertilize its own ovaries selffertilization aka selfcross can happen naturally or can be done purposefully Controlled crossfertilization aka cross Remove anthers from a ower to prevent a selfcross Obtain pollen from a different plant use it to fertilize antherless ower OBSERVATIONS Peas can have purple or white owers ower colorljphenotype 0 There exists a white ower allele and a purple ower allele 0 Some purple owered peas when they selfcross produce only purple ower offspring o Other purple owered peas when they selfcross produce a mixture of purple and white owered offspring 0 ALL white owered peas when hey selfcross produce only white owered offspring Set up crosses 1 True breeding purple crossed with true breeding white the parenting generation produced offspring ALL purple F1 generation Since all the F1 were purple purple is the allelephenotype White is the allelephenotype 2 Selfcross the F1 Produce F2 75 purple 25 True breeding white 31 ratio between dominant and recessive phenotypes in F2 SAME RATION IN ALL TRAITS 3 Selfcross F2 Produced F3 25 of F2 were truebreeding purple 50 of the F2 were nontrue breeding purple 25 of F2 were truebreeding white Actually a 121 ration in F2 MENDEL39S MODEL FOR GENETICS I Parents transmit discrete information to offspring he called theme quotfactorsquot now known as GENES II Each offspring receives one copy of this gene from each parent III Not all copies of these genes are identical Alleles exist An individual with two copies of the same allele true breeding owers Can be homozygous dominant or homozygous recessive individual with two different alleles Nontrue breeding owers IV Alleles are discrete they don39t blend into one another no light purple owers V In heterozygous individuals one allele is dominant and other is recessive Phenotype dominant allele Punnett Squares Diagrams to predict possible outcomes of a cross Show genotype of individual Traitgene is assigned a letter 0 Individuals have two copies of each gene so two of each letter is present 0 Letter is capitalized if it is a dominant allele and lowercase if it is recessive aee Eg ower color letterP Dominant purpleP recessive whitep Homozygous dominantPP Homozygous recessivepp HeterozygousPp P P Pp P P PP P P PP Pp P PP PP Graphical representation mating and reproducing in multiple generations tracking a single trait Malessquares Femalescircles Mating indicated with a horizontal line between mother amp father connected to offspring Generations on separate rows Individuals with tracked trait are highlighted Genotype of individuals is not always known 0 Sometimes it can be inferred Example from the Dominant pedigree for the cross between the mother and father 0 After looking at the punnet square the Father had to be heterozygous because one of his offspring doesn39t have the trait Mother 9 9 Father Pedigrees for recessive traits Traits are more dif cult to analyze Trait is more rare Need homozygous recessive for the phenotype Heterozygous individuals do not have the trait They are called Two carriers can have offspring with the trait only 25 chance Alleles for recessive genetic diseases are rare in population Two carriers mating is even more rare Inbreeding can increase the chances Examples cystic brosis sickle cell anemia More Complex Genetic Scenarios More than one gene affects a single trait Trait is not binary Has continuous variation Eg height in humans More than two alleles Can result in Multiple alleles each exert their phenotypes Eg ABO blood types in humans 0 3 alleles o O is recessive A and B are dominant O is the most common blood type A and B are pretty rare in the population Genotype Phenotype AA AO B B BO AB 00 Heterozygous is intermediate in appearance between two homozygotes Phenotype Affected by Environment Eg Siamese cat Allele encodes a protein that is only active at low temperature 0 And many many more exist Next Chapter Chromosomes Humans have 23 x 2 46 chromosomes 1x22 are 0 Determine sexual characteristics Humans two versions of sex chromosomesljl X amp Y 22x244 are 0 Not directly involved in sexual development Sex Chromosomes X and Y o X has many genes that are required for life 0 XX biological females 0 Y not required for life 0 Has other genes that alter Xdriven development 0 Leads to the development of biological males 0 XYbioogical male XX and XY are the only normally occurring combinations 0 In other animals sexual characteristics are determined through different mechanisms 0 Some genes not directly related to sexual development are located on sex chromosomes Eg A disease in which blood does not clot properly Genetic disease Rare Recessive Gene on X chromosome Xlinked trait af icted are almost always males IOOOOOOO Example of Hemophilia cross XH Xh X39H Xh no X39H fem have XH no XH Xl xm y390 no yO yo have Xlnachann Female mammals have two X chromosomes Twice as much RNA proteins as malesXY o No could be harmful Dosage Composition In XX cells one X chromosome is inactivated o X in activation Chromosome condenses Not transcribed from Called Barr body Occurs early in development X inactivation leads to 0 Cells in different parts of the body have different X chromosomes active inactive 0 Every female is genetic mosaic 0 Can cause different phenotypes in different parts of the body Eg tortoiseshell cat which are orange and black failure of chromosomes to separate during meiosis Leads to spermeggs with abnormal chromosomes number 0 Too few or too many Resulting offspring will have o Monosomy one copy of a certain chromosome Eg Cri Du Chat o Trisomy an extra third copy of a certain chromosome Eg Down syndrome 0 Most often lethal to embryo 0 Or severe developmental problem 0 Nondisjunction rates increase with age of women 0 Due to the way eggs are made 0 Eggs wait in 61 for years until they are used 0 So when a women is 40 the eggs are very old 0 Doesn t depend on men because sperm is constantly being made Nondisjunction can occur in the sex chromosomes 0 Usually in the eggs XX or O XO zygotes A rare but wellstudied genetic disorders OY is not viable Nondisjunctmn can occur in sperm too more rare 0 XY or O two fertilized eggs fused into a 2ceed embryo o Eg female banned from the Olympics for being XXXY genetically was a man Eg women accused of not being her children s mother after a genetic test came back negative but her uterus was genetically positive Next Chapter A Hypothesis 0 May or may not yet have evidence to support it o The reason for additional observationexperiments A scienti c theory 0 A well subported explanation of some aspect of the natural world 0 Based on reproducible experimentationobservation The most reliable well founded explanation in science A scienti c law m better supported theory Like a theory A well supported explanation of some aspect of the natural world Based on reproducible experimentationobservation Tied with theory for the most reliable well founded explanation in science Its narrow in scope explains only a piece of something 0 Can be proved false if new data better supports a new explanation 0 Change in the genetic makeup of a population over time 0 Evolution occurs at the population level I is all organism of the same species in the same area 0 Individuals do not evolve 0Change in the genetic makeuo of a population over time OEvolution is a change in the proportion of alleles I Certain alleles become more or less numerous 0Change in the genetic makeup of a population over time 0 Evolution occurs over multiple generations What drives these changes Natural selection 1 All organisms reproduce exponentially create more 9f themselves To increase total number 2 Population of organisms tend to remain stable 3 Resources are limited Foodspacetht Inference In nature there is a struggle for survival to get resources and only a portion of offspring will survive and reproduce 4 Variation exists within populations phenotypic and genotypic different alleles in different individuals WHY ALL THIS DIVERSITY mutations can create new alleles Gene ow one population mixes with another Can bring in alleles that are novel to a population 5 Much of this variation is heritable passed down genetically lnference The struggle for survival depend on traits whether you can nd food or get to shelter their might be some traits that help them get to the nut or build shelter Not just any traits but traits that are heritable traits that can be passed down genetically Natura selection the few individuals that survive and reproduced will be those that have traits that best help them survive and reproduce and their offspring will have these traits too Natura selection leads to changes in allele frequencies over generations increase in traitsalleles that aid in survival reproduction Eg the Peppered Moth they live in forest with mostly light colored trees have lightcolored wings peppered with black Cooration traitalleles aid in survival help moths hide from predators any cause that reduces the reproductive success of a portion of a population bird predators create selective pressure against mostly dark colored wings and for lighter colored wings moths that don39t blend in get eaten more often despite the advantage of mostly light colored wings still variation in population Light wings common dark wings uncommon Evolution during industrial revolution sootash from nearby factories made trees darker now darker colored wings thrived in survival seective pressure for darker colored wings over several moth generations biologists around these forests they saw more dark colored moths and less light colored moths change in genetic makeup of this moth population over time Devolution caused by natural selection Eg insecticide resistance physical and molecular variations in populations of insects that eat crops different enzymesproteins Might have some alleles that allow them to resist the molecular action of an insecticide Seective pressure is application of insecticide insects with allele that confers resistance survivereproduce better offspring will have this allele too over several generations genetic makeup of population changes evoution Eg Antibiotics and Pathogenic bacteria moecuar variations in bacteria too Antibiotics create selective pressure for bacteria that resist their effects Bacteria populations evolve to resist antibiotics Evolution cannot create the quotPerfect animalquot Natura selection favors survival reproduction in uenced by selective pressure The Theory of Evolution Evolution is Natural selection ie changes occur in the genetic makeup of a population over time because some heritable traits allow organisms to survivereproduce better than others
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