Genetics Exam 1 - Chapter 2

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ProphaseChromosomes condense, become visible; centrioles replicate and move towards poles; the nuclear membrane breaks down; sister chromatids can sometimes be seenCohesinA multi-subunit protein complex that holds sister chromatids togetherSister chromatidsHeld together by cohesin; share a single centromere; kinetochores assembles on opposite sides of the centromereKinetochoreA fibrous structure within the centromereShugoshinReinforces cohesin at centromerePrometaphaseCentrioles reach opposite poles; microtubules connect centrioles with kinetochores; cohesin is degraded by separase after spindle attachment (except at centromere); chromosomes are pushed/pulled to the metaphase plateMicrotubulesMade of protein called tubulin; forms the miotic spindles; responsible for chromosome movementMetaphaseThe chromosomes are aligned on the _____ plateMetaphase plateA structure that forms at the equator of the cell during metaphaseAnaphaseShugoshin is degraded; cohesin at centromere is cleaved by separase; sister chromatids separate; each sister chromatid is now called a daughter chromosome; kinetochore spindle fibers shorten; daughter chromosomes are pulled to opposite poles of the cellTelophaseChromosomes arrive at poles; spindle fibers disappear; nuclear membrane forms; chromosomes decondense; cytoplasm divides by cytokinesis; cell enters interphaseMitosisCreates two cells, each with the same number of chromosomes as the parent cellMeiosisReduces genetic content (diploid parent cells produce haploid daughter cells); produces sex cells; prevents doubling of genome size during sexual reproductionReductionalMeiosis 1 is called the _____ division stage; the number of chromosomes decreases by 1/2EquationalMeiosis 2 is called the _____ division stage; the number of chromosomes does not changeMeiotic prophase 1Has 5 substages; leptonema, zygonema, pachynema, diplonema, diakinesisLeptonemaMeiotic prophase 1 stage; interphase chromatin begins to condense; chromomeres can be seen; local coiling of DNA (also happens in mitotic prophase); homolog search beginsZygonemaMeiotic prophase 1 stage; chromosomes still condensing; rough pairing of homologous chromosomes occurs; a complex of proteins called the 'synaptonemal complex' begins forming between them; the synapsed homologous chromosomes are called bivalentsPachynemaMeiotic prophase 1 stage; Synaptonemal complex finished developing, leads to intimate pairing at a distance of about 100 nanometers; sister chromatids can be seen; synapsed homologs are now referred to as tetrads; crossing over occurs; chiasmata form between non-sister chromatidsTetradsConsist of pairs of sister chromatids and non-sister chromatids (4)Crossing overA physical exchange of DNA occurs between non-sister chromatidsDiplonemaMeiotic prophase 1 stage; the synaptonemal complex disassembles; each pair of sister chromatids begins to pull apart; but non-sister chromatids are still intertwined at chiasmata; although chiasmata formed in pachynema, they can't easily be detected until diplonema; as diplonema proceeds, chiasmata appear to move towards the ends of the chromatids (terminalization)DiakinesisMeiotic prophase 1 stage; terminalization continues; non-sister chromatids remain loosely associated at chiasmata; nuclear membrane breaks down; the two centromeres of each tetrad attach to spindle fibers; tetrads move to metaphase plateMetaphase 1The orientation of each tetrad relative to the poles is random; a product can inherit any combination of paternal and maternal chromosomes; to determine how many combinations of paternal and maternal chromosomes are possible, use the formula 2 ^ nGametogenesisThe development of gametes varies in spermatogenesis and oogenesisSpermatogenesisHow male gametes are produced (in testes)OogenesisHow female gametes are produced (in ovaries); four daughter cells do not receive equal cytoplasmPrimary spermatocyteUndergoes meiosis 1 to produce two secondary spermatocytesSecondary spermatocyteUndergo meiosis 2 to produce 4 haploid spermatidsSpermatozoaWhat the four spermatids made from secondary spermatocytes develop intoPrimary oocyteDivides into a secondary oocyte and the first polar bodySecondary oocyteDivides into the ootid and second polar bodyOotidDevelops into the ovum (mature egg cell)Polar bodiesThe cytoplasm-deficient _____ produced at meiosis 1 and 2 do not undergo further divisionProphaseChromosomes coil up and condense; centrioles divide and move apart; the poles at opposite ends of the cells are established; the nuclear envelope begins to break down and gradually disappearsPrometaphaseCentrioles reach the opposite poles; spindle fibers form; chromosomes are clearly double structuresMetaphaseCentromeres align on metaphase plateAnaphaseDaughter chromosomes migrate to opposite poles using kinetechore-spindle fiber attachment; centromeres split; disjunction of sister chromatids occursTelophaseDaughter chromosomes arrive at the poles; cytokinesis commences; partitioning of the cytoplasm occursInterphaseChromosomes are extended and uncoiled; the phase is composed for four phases - G1, G0, S, and G2SynapsisThe point-by-point pairing of homologous chromosomes during prophase of meiosis 1BivalentsThose structures formed by the synapsis of homologous chromosomesChiasmataThe structure, when viewed microscopically, of crossed chromatidsSister chromatidsThe 'post-S phase' structure of replicated chromosomesDyadsComposed of two chromatids joined by a centromereMonadA sister chromatidMeiosis 1Chromosome number is reduced to haploid complements, which is achieved by synapsis and their subsequent separationIdenticalIt would seem to be more mechanically difficult for genetically _____ daughters to form from mitosis if homologous chromosomes pairedMitosisBy having chromosomes unpaired at metaphase of _____, only centromere division is required for daughter cells to eventually receive identical chromosomal complementsPachynemaDuring the first meiotic prophase, when does crossing over occur?ZygonemaDuring the first meiotic prophase, when does synapsis begin?DiplonemaWhen are chiasmata first visible?150; 150; 150If one follows 150 primary oocytes in an animal through their various stages of oogenesis, how many secondary oocytes would be formed? How many polar bodies? How many ootids?300; 600If one follows 150 primary spermatocytes in an animal through their various stages of spermatogenesis, how many secondary spermatocytes would be formed? How many spermatids?G1During which stage can cells either exit the cell cycle or become committed to completing the cell cycle?SWhat is the longest stage of interphasePrecise replication of DNAWhich condition is evaluated at the G2/M checkpoint?2 dyadsAssume that you were examining a first polar body and noted that it had one copy (dyad) of each chromosome except chromosome 21. Chromosome 21 was completely absent; What would you expect to be the chromosome 21 complement (only with respect to chromosome 21) in the secondary oocyte?3 21 chromosomesAssume that you were examining a first polar body and noted that it had one copy (dyad) of each chromosome except chromosome 21. Chromosome 21 was completely absent; What consequences are likely in the resulting zygote if the secondary oocyte was fertilized?SpermatogenesisOccurs in males; produces spermatids; daughter cells receive equal amounts of cytoplasm and equal amounts of genetic materialOogenesisOccurs in females; produces polar bodies and ootids; daughter cells receive unequal amounts of cytoplasm and equal amounts of genetic material16A diploid cell contains four pairs of homologous chromosomes designated C1 and C2, M1 and M2, S1 and S2, and W1 and W2; predict the number of different haploid cells that could be produced by meiosis.