bio 151 exam 2 Questions And Answers

reasons why cells divide (3) - ANS growth repair reproduction cell cycle (order of specific phases) - ANS interphase, prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis what happens in mitosis - ANS -nuclear envelope division and cytokenesis interphase phases - ANS G1 S G2 what is happening in G1? - ANS growing, making more organelles checkpoint of G1 - ANS G1/S G2 - ANS protein synthesis and preparation for division, check to make sure DNA is replicated checkpoint of G2 - ANS G2/M what is happening in S phase - ANS DNA replication (dna duplicated) at the end the cell has twice as much checkpoint of S phase - ANS none M phase - ANS mitosis (nuclear division) cytokinesis (cytoplasmic division) checkpoint of M phase - ANS m reasons why the cell cycle must be tightly regulated (4) - ANS 1. too much division gives cells when the organism does not need them 2. not enough division means no cells when the organism needs them 3. dividing too early and there might be problems with DNA 4. entering anaphase too early could mean nbiorientation not achieved and could get aneuploidy (presence of an abnormal number of chromosomes in a cell) what is being checked at the G1/S checkpoint - ANS DNA damage checkpoint: (occurs before entering S phase) Is DNA damaged? what is being checked at the G2/M checkpoint? - ANS DNA replication checkpoint: (at the end of G2) Is all DNA replicated? what is being checked at the M checkpoint? - ANS spindle checkpoint (before anaphase): are all chromosomes attached to the spindle what is significant about the "start" (G1/S) checkpoint ? - ANS cells are committed to divide or die what controls the checkpoints? what are the concentrations of these proteins throughout the cell cycle? - ANS active cyclin/CDK complexes CDK levels stable; cyclin levels vary what is the role of Rb - ANS "check" inhibits E2F what is the role of E2F? - ANS turns transcription on-- progress into cycle what stops the cell cycle from processing? what drives it - ANS Rb, "gas pedals" E2F and cyclin/CDK explain diagram with DNA damage - ANS -start checkpoint -when DNA damage detected -- activates p53 -p53 activates p21 -p21 inhibit CDK/cylcin explain diagram with pRb - ANS Rb inhibiting E2F CDK/cyclin phosphorylate Rb Phosphorylated Rb releases E2F E2F leads to cell cycle progression Occurs at each checkpoint what stops the cell cycle from progressing? - ANS Rb "checks" what drives the cycle cycle? - ANS E2F & cyclin/CDK "gas pedals" what checkpoint does DNA damage occur in? why? what is the role of p21? - ANS G1/S Inhibits cyclin/CDK so Rb cannot be phosphorylated Cell death what would happen if there was a mutation in G2/M checkpoint where it could not stop the cell cycle from processing? - ANS incomplete DNA passed entry to M phase what if G1 checkpoint was mutated to allow all cells to continue the cell cycle? - ANS damaged DNA could be replicated --- passed on what if G2/M checkpoint mutated to allow all cells to continue the cell cycle? - ANS incomplete DNA passed onto daughter cells premature entry M phase what if M checkpoint was mutated to allow all cells to continue the cell cycle - ANS premature division uneven amount of DNA in daughter cells when the cell has the most DNA (phase of cell cycle) - ANS G2 when the cell decides whether to divide or die (phase of cell cycle) - ANS G1/S checkpoint when DNA replication occurs (phase of cell cycle) - ANS S when chromosomes line up for separation (phase of cell cycle) - ANS m-checkpoint what is CDK - ANS cyclin dependent kinase , which must be bound to cylcin what is cyclin - ANS activates CDK and targets its protein what is the purpose of the CDK-cyclin complex - ANS conc. of active complexes controls which phase is happening drives cell cycle forward during what phase does a cell have the most DNA - ANS G2 when does the DNA damage arrest cells - ANS G1/S checkpoint what happens if S-cyclin cannot be ubiquitinated - ANS cells stuck at G2/M what are the corresponding base pairs to this sequence: 5'-ACGTTGACGTAT 3' - ANS 3'TGCAACTGCATA5' 5'ATACGTCAACGT3' what connects the two strands of the helix together? where do they attach? - ANS H-bonds connects nitrogenous bases which way is DNA always read? - ANS 5'--3' where does the next nucleotide get added? - ANS 3' end requires triphosphate what must be active first in order for DNA replication to occur? - ANS helices needs to unwind DNA