Bio 1A03 Test 3 Questions and Answers Verified 100% Correct

Bio 1A03 Test 3 Questions and Answers Verified 100% Correct how does cyclin-cdk regulate mitosis? - ANSWER -cyclin-cdk binds to kinases (constant concentration) in order to activate them. these kinases then phosphorylate and activate proteins needed to break down the nuclear envelope, regulate assembly of microtubules, etc S cyclin-CDK - ANSWER -helps initiate DNA synthesis (cyclin A + cdk 2) G1/S cyclin-CDK complex - ANSWER -prepares cell for DNA replication Mitosis checkpoints - ANSWER -G1/S checkpoint, if cell is ready for DNA synthesis (DNA Damage checkpoint) G2 Checkpoint: Is everything replicated/cell ready for mitosis? Pre-Anaphase checkpoint: All chromosomes attached to spindle fibers? How does the G1/S checkpoint work? - ANSWER -If damage to DNA is present, kinases phosphorylate the gene for p53, increasing the production of its protein which accumulates in the nucleus and acts a transcription factor for the inhibitory proteins. These proteins bind to and block G1/S cyclin-CDK complex so that the cell can repair DNA. How does the spindle-assembly checkpoint work? - ANSWER -Unattached kinetochores release a "wait" signal from the lack of tension that recruits checkpoint proteins. These remain until all kinetochores are attached to micotubules. Seperase breaks apart sister chromatids semiconservative replication - ANSWER -each new DNA molecule consists of one new strand and one old strand conservative replication - ANSWER -2 parental strands rejoin after replication dispersive replication - ANSWER -all 4 strands mix together How was the semiconservative model confirmed? - ANSWER -Meselsohn & Stahl created DNA strand out of radioactive isotope of Nitrogen, replicated DNA, used centrifuge to separate the strands and used the placements of the new bands compared to the original strand to prove this model prokaryotic vs eukaryotic DNA replication - ANSWER -Prokaryotes: only 1 ORI, replication moves in both directions due to circular DNA, no gaps in DNA Eukaryotes: multiple ORI, okazaki fragments/dna ligase, free phosphate on 3' end of strands, telomeres (DNA shortening) RNA primer - ANSWER -5-10 nucleotide sequence that binds to BP with template DNA strands so DNA Pol can begin replication (can only add to an existing strand) After fragment/strand is complete, another DNA pol replaces the primer with DNA nucleotides leading strand - ANSWER -3'-5', only req's 1 primer lagging strand - ANSWER -5'-3', multiple primers (one per okazaki fragment), replicates *away* from replication fork Helicase - ANSWER -breaks Hydrogen bonds between base pairs topoisomerase II - ANSWER -relieves the stress of unwinding the DNA for helicase by uncoiling/straightening it single stranded binding proteins (SSBs) - ANSWER -bind to each side of the DNA ladder keeping it from bonding back together during DNA replication RNA primase - ANSWER -synthesizes RNA primers for DNA replication Initiator proteins for DNA replixation - ANSWER -Helicase, SSBs, topoisomerase II DNA polymerase I & III - ANSWER -dna pol I : elongation/synthesis/adding nucleotides dna pol III : removes RNA primer & replaces with DNA (prokaryotes only; eukaryotes different) Reason for Telomeres and Telomere shortening - ANSWER -the last RNA primer on the lagging strand (3' end) has no 3' hydroxyl for DNA pol to attach to and replaxe these nucleotides once they are removed (unlike in prokaryotes) leading to shorter and shorter ends of DNA What are telomeres? - ANSWER -ends of chromosomes designed to protect from DNA shortening. Made of of 100s-1000s of TTAGGG tandem repeats. get increasingly short with each division especially in somatic cells telomere shortening does not occur in which types of cell? - ANSWER -gametes and stem cells. they contain telomerase, a reverse transcriptase that binds to the ends of the tails and adds repeats. potentially useful for aging/cancer karyotype - ANSWER -A display of the chromosome pairs of a cell arranged by size and shape. ploidy - ANSWER -number of sets of chromosomes in a cell haploid vs diploid - ANSWER -one set of chromosomes vs two sets of chromosomes mitotic spindle - ANSWER -a structure made of microtubules that controls chromosome movement during mitosis unlike animals, during cell division, plant cells do not contain ____ - ANSWER centrosomes (though they do have mitotic spindle). final location defines the poles.