Week of 10/23 Notes
Week of 10/23 Notes BIOL 1124
Popular in Intro Biol: Molecule/Cell/Phys
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This 5 page Class Notes was uploaded by Bailey Brimfield on Friday October 30, 2015. The Class Notes belongs to BIOL 1124 at University of Oklahoma taught by Broughton in Fall 2015. Since its upload, it has received 42 views. For similar materials see Intro Biol: Molecule/Cell/Phys in Biology at University of Oklahoma.
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If Bailey isn't already a tutor, they should be. Haven't had any of this stuff explained to me as clearly as this was. I appreciate the help!
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Date Created: 10/30/15
1023 Mendel O O In the mid 18005 there were two primary gene theories Blending inheritance gametes had genes that fuse at fertilization Particulate inheritance each gene is physically distinct and remains intact Austrian monk named Mendel tests this at an abbey using pea plants they are true breeding owers and therefore ideal test subjects Mendel39s Experiment 0 0 Parent generation P generation First lial generation produced by crossing of two different parent plants f1 Second lial generation produced by selfpollination of f1 f2 Parent generation wrinkled x smooth F1 all smooth peas F2 34 smooth peas 14 wrinkled peas If a trait appears in f1 it is dominant If it doesn39t resurface until f2 it is recessive Recessive traits still remain in the genotype they are just not expressed in the phenotype Genes are not quotblendedquot away like hypothesized in blending inheritance theory These results aligned with the particulate inheritance theory Mendel39s Laws 0 0 Genes occur in pairs one from each parent Genes of one parent separate during the production of gametes and they recombine with the second parent s genes at fertilization reconstructing a diploid individual Allele different form of a gene pink leaves smooth peas Genotype Alleles present the genetic makeup If S smooth peas and 5 wrinkled peas 2 copies of the same allele homozygous True breeding SS or 55 1 copy of two or more different alleles heterozygous Ss Dominant gene appears in phenotype Phenotype Physically manifested trait in Ss the peas will be smooth even though the genotype contains an allele for wrinkled peas so its phenotype is smooth This naming system is problematic because it only allows two different forms of a gene to be considered A gene must be homozygous for the recessive trait to express the recessive trait Mendel39s Law of Segregation Two copies of a gene separate during meiosis each gamete gets one copy Combined with partner39s genes at fertilization Three ways to get dominant gene expression one way to get recessive gene expression Genotypic ratio 121 Phenotypic ratio 31 Mendelian genetics explain the basic pattern of inheritance Particulate inheritance follows chromosomal pattern of replication and recombination Laws of segregation and fertilization follow basic laws of probability Dominant genes only need one copy to produce their phenotype A single protein may be sufficient to cause a phenotype to be expressed ln recessive homozygosity neither copy produces a protein for a certain phenotype smooth peas and therefore exhibits a recessive trait wrinkled peas Mendel39s Law of Independent Assortment Alleles of different genes sort independently lf genes are on separate chromosomes they sort independently Genes that are on the same chromosome and whose sorting is therefore related are linked genes Mendel conveniently chose traits on different chromosomes and did not have to deal with linkage The Law of Independent Assortment and recombination of chromosomes allows for genetic diversity Linked genes Sort in groups and do not follow the principles of mendelian inheritance SSYY x ssyy Sst SY sy Sy sY four different possible combinations 0 Cancer Genes O O Mutation in oncogenes is typically dominant only needs one mutated copy to express Mutations in tumor suppressor genes are usually recessive needs two mutated copies to express 1026 NonMendelian patterns 0 O Sexlinked inheritance inheritance of a gene on a sex chromosome does not follow the principles of Mendelian inheritance ex dominant and recessive patterns XX female XY male The Y chromosome carries few genes it is little more than a quotswitchquot gene that begins the male developmental process Conversely the X chromosome carries many genes XY males only have one hemizygous O O O 0 If the X chromosome a male inherits has recessive genes those phenotypes will be expressed which does not follow Mendelian patterns of dominant and recessive genes The father gamete sperm determines the sex of the offspring carries either Y or a second X X linked traits typically exhibited by males Females are heterozygous carriers their second X chromosome usually has a gene on it that is dominant over the recessive gene Female exhibition of a recessive sexlinked trait is rare Redgreen color blindness and hemophilia are examples of X linked traits The Search for Genetic Material 0 O O 0 Early 20th century identi cation of genetic molecules and thereby the mechanism of inheritance was unknown Criteria Had to be present in the nucleus speci cally chromosomes Doubles in the cell cycle Twice as much in diploid cells half as much in haploid cells Some transmission pattern of heritable traits DNA and proteins became viable candidates for genetic material DNA was thought to be too simple only comprised of four nucleotides Proteins were the favored candidate Miescher isolates DNA in cell nucleus in 1868 dubbed it quotnucleinquot Grif th39s 1928 experiment Isolated two strains of pneumonia one with a slimy smooth coat that was virulent and one with a rough coat that was nonvirulent Combined dead smooth cells with rough living cells and the combination killed the host mouse even though the virulent cells were not alive Sought the quottransforming substancequot responsible for this phenomenon Avery39s 1944 experiment Prepared puri ed DNA and puri ed proteins from smooth pneumonia strain and mixed rough nonvirulent pneumonia into each DNA transformed the cells into virulent strains proving that DNA is genetic material Many were still unconvinced criticizing his puri cation techniques etc Hershey and Chase39s 1952 Experiment Viruses inject their genetic material into a host cell and their protein capsids remain on the outside of the host cell Hershey and Chase used radiolabeling to identify protein and nucleic acids dyed protein with radioactive sulfur dyed DNA with radioactive phosphorous f protein enters the host cell it would follow that protein was what comprised genetic material The protein remained outside the host cell and DNA was found inside the host cells Proved that DNA is genetic material con rmed Avery39s discovery This study was conclusive con rmed what some others had already suspected What is DNA s structure 0 0 Finding DNA s structure could reveal the inner workings of cell division determine the method of expression of phenotypes explain the diversity of life etc Many types of evidence provided clues to DNA39s structure The quest to determine the structure of DNA was an international very competitive pursuit among many types of scientists physicists biologists chemists The winner f this quotracequot was highly likely to win the Nobel Prize It was known that DNA was a polymer of nucleotides comprised of deoxyribose sugar a phosphate group and a nitrogenous base Forms of bases differ purines 2 rings adenine and guanine Pyrimidines 1 ring thymine and cytosine Chargaff 1950 Found equal proportions in adenineguanine and thyminecytosine in many different species39 DNA not RNA FranklinWilkins Rosalind Franklin used xray crystallography to determine that DNA was heica in shape Watson and Crick Used Franklin39s data without her knowledge possibly obtained from Wilkins Made 3D scale models which suggested Bases form hydrogen bond pairs on interior of two strands Strands are antiparallel running in opposite directions 0 Each purine is paired with a pyrimidine to maintain a constant distance this matches Chargaff39s ndings 0 Double stranded right handed helix with a uniform diameter Storage of genes 0 Millions of nucleotides and base sequences encode huge amounts of information Susceptible to mutation Watson and Crick anticipated a quotcopying mechanismquot based off their data Overall the search for genetic material and its structure inspired many groundbreaking classic experiments