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BSCI222: EXAM 1 REVIEWo Lecture 1 Material: Chromosomes/Mitosis/Meiosiso Chapters 1 & 2(5, 6, 7, 8, 11, 13, 14, 18, 19, 21, 22, 23, 25, 28, 33)oo Features of the Cell CycleStage Major FeaturesG0 Phase Stable, nondividing period of variablelengthInterphase - G1 PhaseChromosomes: 4DNA: 4Growth and development of the cell; G1/S checkpoint S PhaseChromosomes: 4DNA: 4  8Synthesis of DNA G2 PhaseChromosomes: 4DNA: 8Preparation for division; G2/M checkpointM Phase - ProphaseChromosomes: 4DNA: 8Chromosomes condense and mitotic spindle forms PrometaphaseChromosomes: 4DNA: 8Nuclear envelope disintegrates, and spindle microtubules anchor to kinetochores MetaphaseChromosomes: 4Chromosomes align on the metaphase plate; spindle-assemblyDNA: 8 checkpoint AnaphaseChromosomes: 8DNA: 8Sister chromatids separate, becoming individual chromosomes that migrate toward spindle poles TelophaseChromosomes: 4DNA: 4Chromosomes arrive at spindle poles,the nuclear envelope re-forms, and the condensed chromosomes relax CytokinesisChromosomes: 4DNA: 4Cytoplasm divides; cell wall forms in plant cellso Comparison of Mitosis, Meiosis I, and Meiosis IIEvent Mitosis Meiosis I Meiosis IICell Division Yes Yes YesChromosome reductionNo Yes NoGenetic variation producedNo Yes NoCrossing over No Yes NoIndependent assortmentNo Yes NoMetaphase Individual chromosomes line upHomologous pairsline upIndividual chromosomes line upAnaphase Chromatids separateHomologous chromosomes separateChromatids separateo Sources of Genetic Variation in Meiosis Crossing Over- PROPHASE 1 OF MEIOSIS- Exchange of genes between nonsister chromatids (chromatids from different homologous chromosomes)- Shuffles alleles on the same chromosome into new combinations- Crossing over is the basis for recombinationo Creating new combinations of alleles on a chromatid Segregation (Mendel’s first law)- ANAPHASE 1 OF MEIOSIS- Of homologs- Each individual diploid organism possessed two alleles forany particular characteristic- These two alleles segregate (separate) when gametes areformed, and one allele goes into each gamete- Each individual possessed two alleles encoding a trait, alleles separate when gametes are formed, alleles separate in equal proportions Independent Assortment (Mendel’s second law)- ANAPHASE 1 OF MEIOSIS- Alleles at different loci separate independently- The random assortment of maternal and paternal chromosomes shuffles alleles on different chromosomes into new combinationso Structure of Chromosomes Telomere, centromere, two sister chromatids, kinetochore, spindle microtubules Bivalent/Tetrad- each homologous pair of synapsed chromosomes consists of 4 chromatids Metacentric- centromere in middle Submetacentric- centromere gradually moving up Acrocentric Telocentric- centromere at top Cohesion controls the separation of chromatids and chromosomes in mitosis and meiosis Chiasma/Chiasmata- the physical exchange of DNA between homologous chromosomeso Ploidy: 1n=2 and 2n= 4o Spermatogenesis- the production of gametes in a male animal Spermatogonium (2n)  Primary spermatocyte (2n)  Secondary spermatocyte (1n)  Spermatids (1n) o Oogenesis- the production of gametes in a female animal Oogonium (2n)  Primary oocyte (2n)  First polar body/Secondary oocyte (1n)- the secondary oocyte completes meiosis II, producing an ovum and a second polar body, which also disintegrates  Second polar body/Ovum (1n)- in some animals, meiosis II takes place after the sperm has penetrated the secondary oocyteo Sperm and ovum fuse at fertilization and produce a diploid (2n) zygoteo Lecture 2 Material: Basicso Chapters 2 & 3(1, 2, 5, 8, 10, 11, 14, 15, 16, 20, 22, 25, 29, 36)o Gene- a factor responsible for a characteristico Locus- location of a gene in the genomeo Allele- form of geneo Dominant/recessive- Mendel’s peaso Monohybrid cross: Rr x Rro Dihybrid cross: RrGg x RrGg 16 combinations Following two loci on different chromosomes, no crossing overo If you know the genotype/phenotype relationship, then you can predict ratios of phenotypeso Lecture 3 Material: Basics & Genotype/Phenotype relationshipso Chapters 3 & 5(1,2,3,4,12,13,14,15,17,18,19,22,25,26,28,29,30,31,37,39)o Ch. 3 Probability The law of ‘and’ (multiplication)- P(x and y)= p(x)*p(y)- What is the probability of flipping a coin twice and gettingheads both times?o Probability of getting heads= ½o ½ * ½= 1/4 The law of ‘or’ (addition)- P(x or y)= p(x) + p(y)- What’s the probability of throwing either a 3 or a 4 when you roll a die?o Probability of rolling a 3= 1/6o Probability of rolling a 4= 16o 1/6 + 1/6= 1/3 Multilocus Problems, unlinked loci*- AABbDdEeGg x AaBbDdEeGgo What is the probability of (AABBddEegg)?o 25 gamete types from each parent= 1024 gamete combinationso p(AA) * p(BB) * p(dd) * p(Ee) * p(gg)o ½ * ¼ * ¼ * ½ * ¼ = 1/256- Data often do not match expectations exactly  Chi Square*- “Goodness of fit” chi-square testo if you expected a 1:1 ratio and produced 22 brown and 18 yellow, you wouldn’t be surprised that it’s not perfect 1:1o Reasonable to assume that chance produced the deviation between the expected and observed results- X2= (Observed – Expected)2/ Expected- Observed: observed data in each categoryo Numbers, not fractions or frequencies- Expected: expected data in category based on the experimenter’s hypothesis/model- Degree of freedom= n-1- P-valueo A measure of how significant the calculated value is—stands for probabilityo A big p-value means that the calculated value couldprobably have happened by chance processo A small p-value means there’s only a small probability that the calculated value arose If p-value is less than 0.05 a significant difference exists between the observed and the expected values in a chi-square test. P=0.05 threshold- Reject the null hypothesis if x2calc > x2crito Types of Dominance Complete dominance: DD and Dd= D phenotype- D completely masks the d allele Incomplete dominance: Dd= phenotype between D and d- Phenotype of the heterozygote is intermediate, falls between the phenotypes of the two homozygotes- Ex. red and white flower= pink flower Co-dominance: D phenotype and d phenotype- The heterozygote expresses the phenotypes of both homozygoyes- Ex. MN bloodtypes, blood-type antigens- Ex. red horse and white horse= roan horse (red and white) Dominance Series: involves multiple

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