Biology Study Guide Exam 3I. Punnett SquareP (parental generation) > F1 (filial first generation) > F2 (second generation)II. Mendel’s Model of Hereditya. alternate versions of genes (alleles) account for variation in inherited charactersb. for each character, an offspring inherits two alleles, one from each parentc. if two alleles at one loci differ then the dominant allele will determine appearance, the recessive will have no noticeable affectd. Law of Segregation (shown in monohybrid cross): two alleles for a heritable character will separate during gamete formation and end up in separate gametes, a sperm and egg gets one of the two alleles III. Mendel’s Law of Independent Assortment (shown in dihybrid cross): each pair of alleles separated independently of other alleles. In other words two traits like smooth and green or rough and yellow do not transfer together. Characters are not linked as long as they are on separate chromosomes. IV. Co-dominanceBoth alleles of the same gene affect the phenotype in separate distinguishable waysexample:* can also be Rh+ or Rh-V. Incomplete Dominanceneither allele is completely dominant, so the phenotype of the offspring is intermediate between the pheno-types of the two parental varietiesVI. Epistasisthe phenotypic expression of a gene at one locus affects the expression of a gene at another locusexample:mouse and color coat- one set of alleles determines whether it will be brown or black- another set of alleles will determine if color will be deposited in the coat- albinos do not have the gene to deposit color, not matter if they have the gene to be brown or blackVII. Pleiotropy a gene with multiple phenotypic effectsexample:symptoms of inherited diseases like sickle-cell diseaseVIII. DNA drawingIX. Sex linked recessive genes- always carried on X because the X carries most genes- father’s pass sex linked genes to all their daughters (X) but none of their sons (Y)- any male receiving a recessive gene from his mother will express that trait- far more males have sex-linked disordersX. Morgan’s experimentAll F1 offspring have red eyes because the mother was WW, so both kids expressed the dominant (red eye) gene from her. The F2 generation has a boy with white eyes because the mother from F1 was Ww (she got the w from her white eyed father) and gave her son the recessive allele. The Y of that son could not counter-act the recessive allele (w) because Y mainly determines sex.XI. Barr bodiesone of a female’s X chromosomes is inactivated to prevent the production of twice the normal about of pro-teins, the inactivate X forms a Barr Body- this is done my methylation of DNA bases- cell will randomly choose which X to inactivateexample:calico cat- different cells inactivated different alleles for color resulting in mottled black and orange furXII. Crossing over- the reciprocal exchange of genetic mat. between non-sister chromatids during prophase I of meiosis- the closer two genes are the less likely they are to cross over- the further away genes are on chromosome the more likely they are to cross over- accounts for the recombination of linked genes- provides genetic diversityXIII. Griffith Experimentshowed there was a transforming factor- the heated pathogenic strand when mixed with the non-pathogenic caused the mice to die because the non-pathogenic strand had taken up the deadly DNA of the pathogenicXIV. Hershey Chase experimentPhage’s protein was labeled with radioactive sulfur, and another’s DNA was labeled with radioactive phos-phorus. The phages inserted its transforming factor which was unknown at the time into bacteria. Both bac-teria were separately centrifuged. The more dense cell parts of the bacteria formed a pellet. In the first bac-teria the pellet was colorless and the less dense liquid above was pink. This showed that the protein of the phage was not inserted into the bacteria because it was still in the outside contents. The second bacteria’s centrifuged test tube had a blue pellet of the its cell parts and a colorless, less dense liquid. Therefore the DNA of the phage was what was inserted into the bacteria, because it was blue.XV. Semiconservative experiment- bacterial DNA was labeled with a heavy isotope- then it was labeled with a lighter isotope- the DNA centrifuged after the first replication appeared as one strand- the DNA centrifuged after the second replication appeared as two strandsThere was one layer from the first replication because both the replicated strands contained one original andone new DNA strand. After the second replicated from one of those DNA there was a strand with two new strands and then another with one original strand and one new strand. The two different densities caused two layers in the centrifuged test tube. *this disproved the dispersive and conservative models, and confirmed the semiconservativeXVI. DNA replicationhelicase- unzips DNA double strandorigin of replication- where replication beginsleading strand- strand going in the 5’ to 3’ direction that makes for a continuous replicated DNAlagging strand- strand going in the 3’ to 5’ direction that can only be replicated discontinuouslyprimase- makes the primerprimer- binds to the DNA template strand so that DNA polymerase III can bind and do its thingDNA polymerase III- binds to the primer and adds complementary nucleotide bases to the template strandOkazaki fragments- segments of the replicated strand of the lagging strand because it cannot be replicated continuouslyligase- seals together the Okazaki fragmentssingle strand binding proteins- keeps the two DNA template strands apart so they can be replicatedtopoisomerase- releases the torsion up stream of replication that is created by the helicase’s unwindingDNA polymerase I- replaces the primers on the lagging strandtelomeres- non-coding nucleotides added to the end of the DNA strand to prevent degradation of important nucleotide sequence telomerase- forms telomeresXVII. Cell cycleG1: cell growth, organelles reproduceS: synthesis of DNA G2: continued cell growth(cyclin gets degraded and accumulated throughout the cycle)checkpoints:G1 > is the cell ready to divide, yes enter S, no enter G0G2 > are we ready for mitosis, is there enough MPF (cyclin accumulated and bound to CDK)MPF is maturation promoting factor it works by disintegrating the nuclear envelope and causing chromo-somes to condenseM > are chromosomes lined up at the metaphase plate
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