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28 Cards in this Set
- Front
- Back
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Compare the amount of DNA in eukaryotes with the amount of DNA in prokaryotes.
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Euks have a lot more.
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How is nuclear DNA packaged into chromosomes? Describe the different 'stages' DNA goes through.
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Double helix associates with histones to form Beads On String (now known as CHROMATIN)
Keep and pack until you get chromosome (maximally condensed) |
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What is a nucleosome?
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a nucleosome core particle and linker DNA, i.e., DNA wrapped around a core histone and between each histone is linker DNA
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How many types of Histones are there? What does Histone 1 do? And the rest?
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6 types:
Histone 1: binds linker DNA and NCP to help package chromatin Histones H2A, H2B H3, and H4: form NCP H5: does what H1 does in some cells |
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If a nucleosome were exposed to a nuclease what would happen?
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Digest linker DNA and would get nucleosome core core particle
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How would you dissociate DNA from a nucleosome core particle?
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High salt concentration
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Describe the structure of the nuclear envelope. What organelles is it continuous with? What structures/proteins does it associate with?
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Inner and outer membranes with nuclear pores
Outer nuclear membrane (ONM): continuous with ER and may have ribosomes INM: binding sites for lamins and chromosomes |
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What would an interphase nucleus look like under a microscope?
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Looser than usual; uncondensed chromatin!
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What types of diffusion can nuclear pores permit?
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free diffusion for small molecs, active transport for larger macromolecules
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What proteins comprise the nuclear pore?
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nucleoporins
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How would a molecule larger than 40,000 daltons enter the nucleus? Describe the molecular process.
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Requires a nuclear localization signal and ATP (active transport)
Nuclear transport receptor (floating on a bunch of hairs, aka nuclear fibrils) associates with sequence Fibrils (hairs) guide receptor/protein complex to nuclear pore (which opened when receptor bound sequence) |
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What are lamins? What do they do?
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IMs found in nucleus; form lattice to
1) determine nuclear structure 2) anchor interphase chromosomes |
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What comprises the nucleolus? What goes on in there?
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rRNA and ribosome subunits they produce
Ribosome subunit is 45S but gets modified (and cleaved) into three subunits; these then assemble in different quantities to form ribosomal subunits |
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What occurs in S phase?
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S: Chromosomes replicated
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What occurs in G2 phase?
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G2: phosphorylation (CRUCIAL!) causes chromosome condensation, spindle formation, breakdown of nuclear lamina and envelope
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What occurs in anaphase? How?
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Chromatids separate
Anaphase A: Kinteochore MT's depolymerize, pulls chromatids toward poles Anaphase B: Kinesin causes sliding between associated interpolar MT's (not attached to kinetochore, just attached to each other), causing poles to push apart |
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What occurs during metaphase? How?
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Chromatids line up at equator
2 centrosomes form poles and serve as MTOC's Interpolar MT's have plus ends interacting with kinetochore Aster MT's anchor poles to cell cortex |
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Describe when and how centrioles are replicated and distributed.
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In G1, centrosome has pair of centrioles perpendicular to one another, they then separate by few microns
In S phase, new centriole grows perpendicularly to each of original centrioles, this is complete by G2 In Prophase, centrosomes separate and have their own pairs of centrioles |
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Why is chromosome condensation important in mitosis? What protein facilitates this?
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Helps sister chromatids line up side by side, and prevents chromatomes from tangling together during mitosis
Condensin is involved |
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During what phase does spindle formation occur? How?
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Prophase
2 centrosomes form poles and serve as MTOC, start growing MT's But they grow and shrink Eventually get some overlap of MT's from opp poles KINESIN slides MT's past each other, pushing apart poles |
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What happens in prometaphase? Describe the process.
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Nuclear envolpe disperses and plus ends of MT's probe into condensing chromosomes
Attach to kinetochores; when attached on opposite sides of kinetochore, there is tension, signaling MT's to pull away. If there's no tension, means interpolar MT's aren't bound to both sides, MT's break away and try again |
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On a subatomic level, describe what happens to MT's as they associate with the kinetochore.
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Fibrils on kinetochore (may be called collar) attaches to MTs; dynein on collar pulls kinetochore toward (-) end, allowint MT's to polymerize/depolymerize while still attached to kinetochore
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What region are sister chromatids attached? What protein facilitates this? What happens to it during anaphase?
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Centromere
Cohesin It's destroyed by anaphase promoting complex |
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What does tubulin do?
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Maintains overlap of interpolar MTs
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What roles do astral microtubules play in the cell cycle?
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Anchor MTOC to plasma membrane, but can also use dynein to pull MTOC closer to it; thus pulling apart poles
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What occurs in telophase? How?
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Dephosphorylation in ANAPHASE causes reassembly of nuclear lamina, envelope, and pores
Also causes spindle MT's to depolymerize, chrosomomes to decondense Also causes rRNA transcription to resume, causing nucleolus to reform |
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What occurs during cytokinesis? How?
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Still have some interpolar MT's associated
They form a central spindle, which creates a narrow bridge of cytoplasm Actin and myosin-II form a contractile ring, which creates cleavage furrow Golgi vesicles fuse with membrane to provide extra membrane needed for furrow and daughter cells. Cell breaks into two daughter cells. |
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Do prokaryotes have organelles? Histones?
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No and no.
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