Unit 6 Test Guide
Terms in this set (75)
Why does DNA condense or "super coil" into chromosome?
1. Easier to move during division.
2. So it fits in the nucleus.
5 um uncoiled DNA.
-Deoxyribose sugar (A, T, G, C)
Polymer of DNA nucleotides.
-Made of monomer ATGC
Proteins DNA wrap around.
DNA WRAPPED around the histone proteins.
Coils of nucleosomes
Coils of 30nm fibers; interphase.
Replicated (only in prophase and metaphase). Un-replicated in prophase and metaphase
Why does DNA stay coiled around histone proteins?
DNA- negative charge.
Histone proteins- positive charge.
(Refer to image) Nucleosomes
The basic packaging of DNA in eukaryotes.
-Made of eight histone proteins (octamer) in a core with two wraps of DNA and an H1 histone protein.
The DNA between adjacent nucleosomes.
Links adjacent nucleosomes together and binds the DNA to the octamer core.
-Replicated chromosome )(
Un-replicated daughter chromosomes
Chromatin (Refer to image)
DNA not tightly coiled, but has histones: I, G1
Replicated chromatin: S phase
Replicated DNA, not supercoiled: I, G2
Replicated chromosome: Pro.
Supercoiled, replicated DNA: Metaphase
Supercoiled, but no longer attached: Anaphase
(Look at the graphic image)
(Look at the visualizing nucleosomes thing)
Interphase is what?
A very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
Metabolic reactions that occur during interphase are:
-Majority of cell cycle is in G1, S, G2.
G1: Specialized functions; need proteins synthesis.
S: DNA replication occurs (nucleus).
The events that take place in a cell leading to its division that produces two daughter cells.
G1 (first gap phase)
-Cells performing differentiated function.
-A LOT of protein synthesis and metabolism.
-Numbers of organelles increase.
S (synthesis phase)
The cell replicated the DNA in the nucleus so that after mitosis both cells have a set of genes.
G2 (second gap phase)
-Protein synthesis and metabolism is occurring to create molecules needed for mitosis.
-Number of organelles increase.
Division of the cell nucleus into two genetically identical daughter nuclei.
The division of the nucleus into two genetically identical daughter nuclei.
What are the four processes that involve mitosis?
1. During embryonic development.
2. Organism growth.
3. Tissue repair.
4. Asexual reproduction.
What are the four stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase
Interphase (S and G2)
What four events occur during prophase?
1. Nuclear membrane begins to break down.
2. Nucleolus disappears
3. DNA super coils into replicated chromosomes (condenses)
4. Mitotic spindle fibers form and centrosomes (from two centrioles) move toward cell poles.
Outline the process of metaphase:
-Replicated chromosomes align at the central equator (metaphase plate).
-A protein complex (kinetochore), located at the centromere (sister chromatids attach), is connected to microtubules (spindle fiber)
Outline the process of anaphase:
-The identical chromatids (un-replicated chromosomes) are pulled towards the poles of the cell by motor proteins moving alone kinetochore microtubules.
-Non-kinetochore microtubules elongate cell.
Outline the events that occur during telophase:
-Nuclear membrane reforms.
-Chromosomes de-condense into chromatin.
-Spindle fibers break apart.
Occurs after mitosis and is different in plants and animal cells.
-Division of the parent cell cytoplasm and organelles into two daughter cells.
Difference between mitosis and cytokinesis is:
-Mitosis is the division of the nucleus (and DNA in it).
-Cytokinesis is the splitting of the cytoplasm and organelles.
Cleavage furrow in animal cells cytokinesis is what?
Contractile proteins form rings at the equator of the cell.
-Proteins then contract and form a cleavage furrow, pinching in the cell membrane unity; splits.
Describe the formation of the middle lamella and the cell wall in plant cell cytokinesis.
-Golgi body buds off vesicles; contains pectin (sticky polysaccharide).
-Vesicle moves towards cell equator and fuse together.
-Pectin becomes "middle lamella" and anchors daughter cells together.
-More vesicles secrete cellulose to form the cell wall.
Cytokinesis in plant cells:
1. Vesicles move to equator where they fuse to form tubular structures across the equator.
2. Tubular structures merge to form two plasma membranes of the two daughter cells. (div. = done)
3. Pectins/other deposited between two membranes by exocytosis, forming middle lamella.
4. Cellulose brought to the middle lamella by exocytosis.
Cytokinesis in animal cells:
1. Cleavage furrow is created using a ring of contractile protein, actin, and myosin.
2. The cleavage furrow reaches the center.
3. The cells are pinched apart into two, separate daughter cells.
(Look at the real-life pictures of the cell.)
cells in mitosis/total cells
(Refer to onion lab in notes.)
Protein that initiates different parts of the cell cycle.
-Family of proteins that control the progression of cells through the cell cycle.
-Cyclins activate CDK enzymes.
Cyclin Dependent Kinase (CDK)
Protein that must attach to a cyclin to work (work=phosphorylation).
-Active CDK complexes phosphorylate to target proteins that do jobs to do the cell cycle.
Cyclin + CDK bound together; can phosphorylate.
An enzyme that adds phosphate groups to
The process of adding a phosphate group to a molecule.
What are the four types of cyclins?
Cyclin D, E, A, B
-Different cyclins are active at different times.
Cyclin D (G1 Cyclin)
-Synthesized during G1.
-High concentration-> goes to next S.
-Cyclin D-CDK complex phosphorylates a protein that suppresses protein.
-Melanoma: cell makes Cyclin D when it should not.
-> Target protein remains active "tumor suppression" is off and cell moves to S when it should not.
-Too many cells move through -> tumor.
Cyclin E (S Cyclin)
-Begins being synthesized mid G1.
-At high concentration, E moves from G1 to S.
-E-CDK complex phosphorylates a target protein to replicate DNA.
-Breast cancer: makes E when should not.
-Protein remains active; DNA prepares for replication when it should not.
-Too many cells in the cell cycle; TUMOR.
-Regulate multiple cell cycle steps b/c it activates two CDKs.
-S: A-CDK initiates replication and ensures DNA replicated every cycle.
-G2: A-CDK prepares centrioles for mitosis.
Cyclin A (2)
-Produced at the wrong time.
Cyclin B (Mitotic Cyclin)
-Necessary for progression of cells into and out of mitosis.
-End of S: B-CDK triggers entry into prophase.
-For anaphase, degradation of B is necessary.
-B is elevated; cells enter mitosis prematurely (divide when should not).
-Anti-cancer therapies designed to prevent B/CDK complex formation in cancer cells to prevent cell division.
Who discovered cyclins and when?
Tim Hunt (British biochemist) in the early 1980s.
-2001 Nobel Peace Prize.
How did Hunt discover cyclins?
-Zygotes from sea urchins in mitosis.
-Samples removed at a time interval.
-Protein from samples ran through electrophoresis.
-Different proteins in the sample separate from each other on the gel.
-One protein, cyclin, accumulated and disappeared.
-Finding something good without looking for it.
-Discovering how the cycle was controlled was not Hunt's intention.
-Role: be observant and curious.
Disease caused by malignant tumors, mass of tissue, due to unregulated cell growth.
Malignant tumors can ____________.
When the cells from a malignant tumor spreads through the body via blood or lymph vessels.
Lack the ability to spread and do not cause cancer.
How does cancer occur?
-Cells become cancerous after mutations accumulate in the genes that control the cell cycle.
-Mutagen induce mutations in DNA, not all mutations cause cancer.
How do mutations arise?
When mutagens, such as UV radiation, change the DNA.
Mutation results in uncontrolled cell division and cancer.
Not all mutagens are ___________.
Normal genes that code for proteins (cyclins) that help the cell move through the cycle.
What happens when proto-oncogenes mutate?
They become oncogenes.
-Oncogenes can move through the cell cycle, even if they should not.
-Can lead to overstimulation of cell division overriding checkpoints.
Genes function to stop cells from dividing when it should not.
-Can mutate, leading to the cell moving through the cycle when it should not.
-Cancer develops when both tumor-suppressors mutate and oncogenes form.
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