Exam 4 - Exam 4 Pre-read pg 262 285 A cell in Anaphase of...

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Exam 4 Pre-read pg. 262- 285 A cell in Anaphase of mitosis will have how many chromosomes and how much DNA compared to that same cell when it was in G2 of interphase? Twice as many chromosomes, same amount of DNA How do the chromosomes move on the spindle? The kinetochore of the centromere moves along the spindle fiber and breaks the spindle fiber down. What determines when a cell divides? What regulates cell division? Cancer is when cells continue to divide when they are not supposed to. Checkpoints o When cells aren’t dividing, they are held in G1 phase. Components of Cell division regulation Cyclin: a protein that varies in concentration depending on the cell cycle Cyclic dependent kinase: remains in constant concentration, dependent on cyclin Maturation promoting factor: Triggers cell division, cyclin and CDK combined Cyclin and CDK in the cell cycle: Throughout the cell cycle, CDK is present. At the beginning of G1, end of cytokinesis, there is no cyclin present. There is a low increase in cyclin in the S phase. In G2, there are high levels of cyclin, which creates MPF for cell division. At the end of cytokinesis, all the cyclin is destroyed. How many chromosomes are required to have one copy of each gene? How many chromosomes are required to have once complete copy of all the DNA needed to code for every protein in an organism? There is no set number of chromosomes. Ploidy Number of sets of chromosomes in a cell Haploid: 1 set, 1n (X) Diploid: 2 sets, 2n (XX) Triploid: 3 sets, 3n (XXX) Tetraploid: 4 sets, 4n (XXXX) Polyploid versus Aneuploid Polyploid: more than two sets of chromosomes Aneuploid: Change in the number of a single chromosome (Down’s Syndrome, etc.) o E.g. In Down’s Syndrome, all chromosomes are diploid, but chromosome 21 is triploid. Homologous Chromosomes Same length Same centromere position Same banding pattern Same GENES, but may not have the same form of the gene Meiosis Produces non-identical daughter cells Not identical to each other
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Not identical to parental cell Reduces number of chromosomes in the cell by half (haploid cells) One cell with two replicated chromosomes to four cells with one unreplicated chromosome each Why half the number of chromosomes? Sexual reproduction Does it matter which chromosomes are in each daughter cell? Yes Prophase I Homologous chromosomes are in synapsis o Synapsis: Pairs of replicated similar chromosomes from each parent o Not connected at centromere o Tetrad formation: pair of homologous chromosomes o Chiasmata: site of crossing-over o Crossing-over Chromosomes break and exchange ends of arms A cell in Anaphase II will have how much DNA compared to when it was in Prophase I? Half as much
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Exam 4 - Exam 4 Pre-read pg 262 285 A cell in Anaphase of...

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