BIOA01 Textbook Notes Chapter 8,10,12,14.docx

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Biological Sciences
Dwayne Pare

11/7/2013 7:31:00 AM Chapter 8- Cell Cycles - Eukaryotic cell division mediated by processes of: DNA replication, a dynamically changing cytoskeleton, cell cycle checkpoints Prokaryotic Cell Division - binary fission: dividing of cell into 2 parts cells have a B period of cell growth, then chromosomes have C period where they are replicated and separated to opposite ends of cell, finally D period where membrane pinches and two daughter cell are formed - nucleoid: where chromosome is compacted in central region in prokaryotic cells - origin of replication (ori): regions where replication of bacterial chromosome occurs cytokinetic ring: the inward constriction of cytoskeletal protein that allows the dividing of DNA - chromatids: two newly created molecules of DNA - spindle: microtubules made of polymerized tubulin protein that forms and segregates chromosomes to their daughter cells without requiring portions of the nuclear envelope seen in yeasts Eukaryotic Cell Division - chromosome is composed of DNA molecules and its associated proteins can have: - diploid: two copies of each type of chromosome in nuclei - haploid: one copy of each type of chromosome in nucleus - ploidy: the number of chromosome sets in a species or cell ex: humans have 23 - nucleolus: nuclear site of rRNA transcription processing and ribosome assembly - sister chromatids: two new, identical molecules - chromosomal segregation: the equal distribution of daughter chromosomes to each of the two cells that result from cell division - before replication chromosome is composed of 1 DNA molecule, after replication it is composed of 2 DNA Mitosis 1 interphase: the cell grows and replicated its DNA in preparation for mitosis G1 phase: cell makes RNA, proteins, not nuclear DNA; only phase that varies among species, can enter a g0 phase where division is arrested S phase: cell duplicates chromosomal proteins and DNA G2 phase: cell synthesize RNAs and proteins, required for mitosis 2. prophase: replicated chromosomes condense into compact rodlike structures nucleolus becomes smaller and disappears while condensing mitonic spindle begins to form between 2 centromeres and they migrate towards opposite ends of the cell forming spindle poles 3. prometaphase: kinetochore formed on each chromatid at centromere and attaches to microtubules from spindle kinetochore: a specialized structure consisting of proteins attached to a centromere that mediates the attachment and movement of chromosomes along the mitonic spindle 4. metaphase: spindle microtubules move chromosomes into alignment at spindle midpoint/ metaphase plate karyotype: collection of metaphase chromosomes arranged according to size and shape of species 5. anaphase: sister chromatids separate and move to opposite spindle poles 6. Telophase: spindle disassembles and the chromosomes at each pole decondense - cytokensis: division of cytoplasm furrow: in animals, groove that girdles the cell powered by microfilaments and motor proteins and gradually deepens until it cuts cytoplasm into 2 parts cell plate: in plants, new cell wall forms between daughter nuclei and grows laterally until it divides cytoplasm Mitotic Spindle - centrosome: site near the nucleus that organizes the microtubule cytoskeleton during interphase and positions the organelles in cytoplasm; found in animal cells and protists main microtubule organizing centre (MTOC) contains centrioles: cylindrical structure consisting of 9 triplets of microtubules, generates microtubules needed for flagella and cilia asters: radiating array produced as microtubules extending from the centrosomes of cells grow in length and extent, at the spindle tips, form poles of the spindle - 2 types of microtubules in eukaryotes: kinetochore: connect the chromosomes to the spindle pole non kinetochore: extend between spindle poles without connecting to chromosomes - during anaphase, chromosomes are moved to the poles by motor proteins in their kinetochores and tubulin units of microtubules disassemble as kinetochore “walks” along them Cell Cycle Regulation - checkpoints: internal control of the cell cycle prevents a critical phase from beginning until all previous phase is complete - cyclin-dependent kinases: a protein kinase/ enzyme that adds phosphate groups to proteins regulating and controls progression of cell cycle; enzymes are switched on when combined with protein cyclin - growth and death factor proteins and peptide hormones bind to receptors on cell membrane which trigger reactions inside the cell that cause regulatory effects - contact inhibition: the inhibition of movement or proliferation of normal cells that results from cell-cell contact - cellular senescence: loss of proliferative (diving) ability over time telomeres: repetitive DNA sequences that are added to the ends of chormsomes by enzyme telomerase cells stop dividing after telomeres reach a minimum length - cancer cells: lose adhesions to other cells and become actively mobile causing metastasis mutations in genes that code for cyclin that disregulated cell division (oncogenes) - apoptosis: programmed cell death caspases: a protease enzyme that is coded by cell death abnormal gene, CED-3 Chapter 10 – Mendel, Genes and Inheritance Garden Peas - the male gametes are sperm nuclei contained in pollen produced in anthers - female gametes are egg cells produced in carpel - self pollination: fertilization from sperm into the carpel/egg of the same plant - cross pollination: fertilization of one plant by a different plant - true breeding: individual that passes traits without change from one generation to the next - P generation parental, F1 first generation, G2 generation - Hypotheses of Mendel: adult plants carry a pair of factors that govern the inheritance of each character (genes) if an individual’s pair of genes consists of different alleles, one allele is dominant over the other recessive allele (dominance= masking effect) the two alleles of a gene segregate and enter gametes singly the alleles of the genes that govern the two characters segregate independently during formation of gametes - alleles: different versions of a gene that produce different traits of a character - Principle of Segregation: Mendel’s principle that pairs of alleles that control a character segregate as gametes are formed and that half the gametes carry one allele and the other half carry the other allele - homozygous: 2 same alleles of the same gene - heterozygous: 2 different alleles of the same gene - monohybrid cross: a cross between two individuals that are each heterozygous for the same pair of alleles (Pp x Pp) - genotype: genetic constitution of an organism - phenotype: outward appearance - probability: possibility that an outcome will occur if it a matter of chance dividing an outcome by the total number of possible outcomes product rule: the probability that events A and B will both occur equals the probability of A multiplied by B sum rule: probability that either A or B or C will occur equals probability of A plus B plus C - testcross: a cross between an individual with dominant phenotype and a homozygous recessive individual - dihybrid: zygote produced from a cross that involves two characters - dihybrid cross: cross between 2 individual that are heterozygous for 2 pairs of alleles (RrYy X RrYy) forms a 9:3:3:1 ratio - Principle of Independent Assortment: Mendel’s principle that the alleles of the genes that govern two characters segregate independently during formation of gametes Sutton’s Chromosome Theory - chromosome theory of inheritance: the principle that genes and their alleles are carried on the chromosomes - chromosomes occur in pairs in sexually producing, diploid organisms, as do alleles of gene - chromosomes of each pair are separated and delivered singly to gametes as are alleles of gene - separation of any pair of chromosomes in meiosis and gamete formation is independent of the separation of other pairs - one member of each chromosomes pair is deriver in fertilization from the male parent and one from the female - locus: particular site on a chromosome at which a gene is located particular DNA sequence that encodes for a protein or RNA responsible for the phenotype - incomplete dominance: occurs when effects of recessive alleles can be detected to some extent in heterozygotes (pink flower between white and red) - codominance: occurs when alleles have approximately equal effects in individuals, making the two alleles equally detectable in heterozygotes (L M and L alleles for blood encoding for types of glycoprotein) - multiple alleles: more than two different alleles of a gene are present, contain nucleotide differences at one or more locations in their DNA ABO blood types exhibit both dominant and co-dominance; 3 alleles of single gene; I , I , i - epistasis: genes interact with one or more alleles of a gene at one locus inhibiting or masking effects of one or more alleles of a gene at a different locus insulin resistance in humans homozygous recessive gene ee in Labradors always masks the other gene (b/B) regardless of which alleles it has - polygenic inheritance: several to many different genes contribute to the same character height involves many different genes on the chromosome quantitative traits: skin colour, body weight, height phenotype is also influenced by the environment - pleiotropy: single genes affecting more than one character of an organism sickle cell disease Chapter 12- DNA Structure, Replication and Organization Establishing DNA as Hereditary - Johann Friedrich Miescher first discovered deoxyribonucleic acid while studying the composition of the cell nucleus. He extracted pus cells from bandages and found the acidic substance with high phosphorus content, and called it nuclein, we now know as DNA, the genetic material of living things. - Frederick Griffith injected mice with S strain, infective, protein coated Streptococcus bacteria caused death; and R strain, no capsule, noninfective streptococcus bacteria didn’t cause death. Injection by heat killed S cells allowed mice to live, however heat killed S cells and R cells caused mice to die. Griffith concluded that dead S cells could genetically change R cells to S cells via transformation Transforming principle: agent responsible for transforming R cells into S cells= DNA (Oswald Avery) - Hershey and Chase bacteriophages: virus: two batches of e coli phages prepared, one with radioactive label on protein, other with radioactive label on DNA progeny phages in 3S medium labeled proteins (sulphur component in 32 proteins) and phages in P medium labeled DNA (phosphorus component of DNA) 32 P isotope was found in phage infected cells and progeny, protein was only found in protein coat indicating that DNA is the genetic material and protein is not - Watson and Crick established that DNA is made up of 5 carbon sugar deoxyribose, phosphate group, ¼ nitrogenous bases purines: double ring structures of carbon and nitrogen, adenine and guanine pyrimidines: single carbon ring structures, thymine and cytosine Chargaff’s rules: # of purines= # of pyrimidines, AT, CG Sugar phosphate backbone: deoxyribose sugars linked by alternating phosphate groups that act as a bridge between 3’ carbon of sugar and 5’ carbon of next sugar; also called a phosphodiester bond the polynucleotide chain has polarity, 5’ end and 3’ are differently charged - double helix model: the two sugar- phosphate backbones are separated from each other by a regular distance, the bases extend into this and fill the central space - complementary base pairing: each strands are complementary to each other, A and T, C and G this causes the two strands to be antiparallel DNA Replication - semiconservative replication: the process of DNA replication in which the two parental strands separate and each serves as a template for the synthesis of new progeny double stranded DNA; each progeny ends up with 1 new strand and 1 parental conservative replication: after copies separate and wind together to an all new helix dispersive replication: mixture of both old and new pieces of DNA interspersed on the same piece - Meselson and Stahl proved that DNA replication is semiconservative: used nonradioactive heavy nitrogen isotope 15N to tag parental DNA and 14 lighter N isotops first grew e coli bacteria in5N labeling the entire DNA and then transferred 14 it to N after each round of replication following the transfer, extracted DNA and put it into a cesium chloride and centrifuged mixture, double helices moved to position in gradient where density/weight matches the CsCl results observed of density only made sense to conclude that semiconservative is the mechanism of DNA replication - DNA polymerase: are type of enzyme that assembles complementary nucleotide chains during replication deoxyribonucleoside triphosphates: substrates for the polymerization reaction of DNA polymerase; nitrogenous base linked to sugar linked to three phosphate groups DNA polymerase can only add to the 3’-5’ end of existing chain, assembling new chain in 5’-3’ direction 3’ OH, 5’ phosphate on ends of chain sliding DNA clamp: protein that encircles the DNA and binds to the rear of DNA polymerase to attach it to template, rate of DNA synthesis speeds up - DNA helicase: an enzyme that catalyzes the unwinding of DNA template strands - origin of replication (ori): a specific region at which the replication of bacterial chromosome commences - replication fork: Y shaped structure consisting of two unwound template strands - single-stranded binding proteins (SSBs): coat the exposed single stranded DNA segments stabilizing the DNa and keeping the two strands from pairing back together - topoisomerase: an enzyme that relieves the overtwisting and strain of DNA ahead of replication fork, prevents tangling - primer: short nucleotide chain made up of RNA that is laid down as the first series of nucleotides in new DNA strand primase: an enzyme that assembles and synthesizes the primer for a new DNA strand during replication RNA primers are removed and replaced with DNA later in replication - discontinuous replication: replication in which a DNA strand is formed in short lengths that are synthesized in the direction opposite of the unwinding Okazaki fragments: relatively short segments of DNA synthesized on the lagging strand to cover up the gaps in DNA Leading strand: DNA strand assembled in the direction of unwinding Lagging strand: DNA strand assembled discontinuously in direction opposite of unwinding - DNA polymerase II: main polymerase, extends the primer by adding nucleotides - DNA polymerase I: removes RNA primer at 5’ end of Okazaki fragme
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