Chapter 12 - Cell Cycle Flashcards
Bi
= two
Centro
= center
Cyclo
= circle
Cyto
= cell
Kinet
= move
Gamet
= a wife or husband
Gen
= produce
Inter
= between
Mal
= bad or evil
Meio
= less
Meta
= between
Pro
= before
Soma
= body
Telos
= end
Anaphase
Fourth stage of mitosis.
Chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.
Anchorage Dependence
The requirement that to divide, a cell must be attached to the substratum.
Benign Tumor
A mass of abnormal cells that remains at the site of origin.
Cell Cycle
An ordered sequence of events in the life of eukaryotic cells. From its origin in the division of a parent cell until its own division into two.
M,G1,S, and G2 phases.
Cell Plate
A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis.
Centromere
The centralized region joining two sister chromatids.
Centrosome
Material present in the cytoplasm of all eukaryotic cells, important during cell division.
The microtubule-organizing center.
Checkpoint
A critical control point in the cell cycle where stop and go-ahead signals can regulate the cycle.
Chromatin
The complex of DNA and proteins that makes up a eukaryotic chromosome.
Chromosome
A threadlike, gene-carrying structure found in the nucleus. Each chromosome consist of one very long DNA molecule and associated proteins.
Cleavage
The process of cytokinesis in animal cells, characterized by pinching of the plasma membrane.
Cleavage Furrow
The first sign of cleavage in an animal cell. A shallow groove in the cell surface near the old metaphase plate.
Cytokinesis
The division of the cytoplasm to form two separate daughter cells immediately after mitosis.
Density-dependent Inhibition
The phenomenon observes in normal animal cells that causes them to stop dividing when they come into contact with one another.
G1 Phase
The first growth phase of the cell cycle, consisting of the portion of interphase BEFORE DNA synthesis begins.
G0 Phase
A nondividing state in which a cell has left the cell cycle
G2 Phase
The second growth phase of the cell cycle, consisting of the portion of interphase AFTER DNA synthesis occurs.
Gamete
A haploid cell, such as an egg or sperm.
Genome
The complete complement of an organisms genes.
An organisms genetic material.
Interphase
The period in the cell cycle when the cell is not dividing.
Kinetochore
A specialized region on the centromere that links each sister chromatid to the mitotic spindle.
Malignant Tumor
A cancerous tumor that is invasive enough to impair the functions of one of more organs.
Metaphase
The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.
Metaphase Plate
An imaginary plane during metaphase in which the centromeres of all the duplicated chromosomes are located midway between the two poles.
Metastasis
The spread of cancer cells to locations distant from their original site.
Mitosis
A process of nuclear division in eukaryotic cells conventionally divided into five stages.
Prophase, prometaphase, metaphase, anaphase, and telophase.
Mitosis conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei.
Mitotic(M) Phase
The phase of the cell cycle that includes mitosis and cytokinesis.
Mitotic Spindle
An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.
Prometaphase
The second stage of mitosis, in which discrete chromosomes consisting of identical sister chromatids appear, the nuclear envelope fragments, and the spindle microtubules attach to the kinetochores of the chromosomes.
Prophase
The first stage of mitosis, in which the chromatin is condensing and the mitotic spindle begins to form, but the nucleolus and nucleus are still intact.
S Phase
The synthesis phase of the cell cycle.
The portion of interphase during which DNA is replicated.
Sister Chromatids
Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meosis II.
Somatic Cell
Any cell in a multicellular organism except a sperm or egg cell.
Telophse
The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.
Transformation
The conversion of a normal animal cell to a cancerous cell.
How long is a cells life cycle?
From the time it was created until it under goes cell division or dies.
Some cell types constantly divide while other will not and other may only divide to repair damage.
Do single cell organisms divide?
They can reproduce by cell division.
Multi-cell organisms use cell division for____.
Growth, development, and repair.
Most important task of cell division?
First to duplicate(replicate) its entire genome(all genetic information) BEFORE it divides.
Ensures daughter cells will be genetically identical.
Genomes are organized into______.
Chromosomes which are segments of DNA nucleotides with associated proteins.
- each chromosome can have 100’s-1000’s of genes
- Prokaryotes have CIRCULAR chromosomes
- Eukaryotes have LINEAR chromosomes
Somatic VS Gamete cells
Somatic are all other body type cells EXCEPT gametes(sex cells)
- Somatic have 2 copies of chromosomes(2 copies of every gene)
- Gametes have one copy of each chromosome(1 copy of every gene)
Female = Egg Gamete Male = Sperm Gamete
Chromosome replication: Sister Chromatids
- chromatids are joined at a central area called the centomere
- Sister chromatids are completely identical to each other in DNA nucleotide sequence.
- They are called chromatids until they separate from each other in anaphase becoming “daughter chromosomes”
2 Major Phases of cell cycle division
- Interphase
2. Mitotic Phase
Interphase(longest phase) subphases
- G1(first gap) Phase - Normal function of cell takes place
- S Phase - DNA synthesis takes place(sister chromatids made)
- G2(second gap) Phase - Preparation for cell division, centrosomes duplicated
Mitotic Phase
- Mitosis: Division of Nucleus
2. Cytokinesis: Division of cytoplasm
Mitosis 5 Subphases
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
Mitosis Phase 1
Prophase
- Centrosomes begin formation of mitotic spindle: network of microtubules begin growing from each centrosome. - Chromatids begin to condense so that each pair begins to be visualized as distinct structures.
Mitosis Phase 2
Prometaphase
- Nuclear envelope disintegrates. - Centrosomes are at opposite ends of cell as mitotic spindle complete. - Pairs of sister chromatids seen distinctly. - Kinetochore microtubules attach to the kinetochores(proteins found at centromeres, one on each sister chromatid) - Non-kinetochore microtubules elongate and push against each other, lengthening cell
Mitosis Phase 3
Metaphase
- Each pair of sister chromatids is brought to the middle of the cell(imaginary metaphase plate) by the opposing pulling action of each centrosome and the kinetochore microtubules attached to those centrosomes.
Mitosis Phase 4
Anaphase
- Sister chromatids are released from each other and begin moving towards opposite poles of the cells by kinetochore microtubules that become shorter. - Called daughter chromosomes now.
Mitosis Phase 5
Telophase
- Daughter chromosomes now at opposite ends of the elongated cell. - Chromosomes begin to become more diffuse and less distinct. - Nuclear enevelopes reform around each daughter nuclei.
Cytokinesis(after Mitosis)
Animal Cells
- Cleavage furrow begins where microfilaments contract in the middle of the cell, eventually pinching apart 2 daughter cells.
Plant Cells
- Cell wall prevents each separation of daughter cells. - Vesicles containing cell wall building materials form a cell plate between 2 nuclei and eventually a complete new cell wall is built, separating the space into 2 daughter cells.
Following Chromosome/Chromatid number in Mitosis
- During the S phase, each chromosome duplicates and is a pair of sister chromatids
Ex. If the 2N=2, there are 2 chromosomes at S phase but each one is a pair of sister chromatids for a total of 4 chromatids - The chromosome number will stay 2N and the total chromatid number will stay that same until anaphase
- Each chromatid will then be called a chromosome again after pulling apart in anaphase
- After cytokinesis, each daughter cell will have the same chromosome number as the original somatic cell
Somatic Cell w/ 4 Chromosomes(2n = pairs)
G1: 4 chromosomes
S: 4 chromosomes; 8 chromatids(4 pairs)
G2: 4 chromosomes; 8 chromatids(4 pairs)
Prophase: 4 chromosomes; 8 chromatids(4 pairs)
Prometaphase: 4 chromosomes; 8 chromatids(4 pairs)
Metaphase: 4 chromosomes; 8 chromatids(4 pairs)
Anaphase: 8 chromosomes; 4 moving to each
Telophase: 4 chromosomes in each daughter nucleus
After cytokinesis: 4 chromosomes in each daughter cell.
CHECK: daughter cells have same as starting chromosomes.
Cell Cycle Control
- The passage of a cell between each stage is monitored by series of checkpoints
- 3 major checkpoints
- G1 checkpoint: Passage through this checkpoint indicates a cell will divide
- If a cell exits the cell cycle at this point, it enters G0 phase (non-dividing state)
- G2 checkpoint: Ensures DNA synthesis took place in S phase and that all necessary cellular material for mitotic phase has taken place including duplication of centrosome - M checkpoint: Ensures that all sister chromatids have separated properly and moved to opposite ends of the cell
- G1 checkpoint: Passage through this checkpoint indicates a cell will divide
Normal Cell Behavior
- Density dependent inhibition: Cells stop dividing if density of cells is too high
- Anchorage dependence: Most cell types need a substrate to attach to in order to divide
Abnormal Cell Behavior(Cancer cells)
- Transformation event turns normal cell into cancerous cell
- Cancer cells lack density dependent inhibition and will continue to divide uncontrollably forming a mass (tumor)
- Tumors can be benign and stay in the original area or
- Malignant because they leave their original site by loss of anchorage dependence
* Metastatic tumors form from cells broken away from original site of first tumor
Why do cells need to divide?
- Reproduction in single cell organisms
- development in multicell organisms
- repair in multicell organisms
3 Phases of Cell Cycle
- Interphase
- Mitotic Phase
- Cytokinesis
Cell Cycle: Phase 1
Interphase
- G1: growth of cell, organelles made - G0: non-dividing stage - S: if committed to dividing, DNA is copied - G2: more growth, preparation for dividing
Cell Cycle: Phase 2
Mitotic Phase(5 subparts)
- Prophase: Chromosomes become visible as they condense, Mitotic spindle begins to form and centrosomes begin moving apart.
- Prometaphase: Nuclear membrane fragments, Kinetochore microtubules attach to kinetochores, non-kinetochore tubules in aster not attached to chromosomes.
- Metaphase: Centrosomes at opposite poles, Chromosomes lined up at metaphase plate with
sister chromatids straddling plate, each attached
to opposite pole by microtubules. - Anaphase: Chromatids separate as kinetochore microtubules shorten and non-kinectochore microtubules lengthen to elongate cell.
- Telophase: Each pole has complete set of daughter chromosomes, begin to become diffuse, daughter nuclei form as nuclear membrane restructures.
Cell Cycle: Phase 3
Cytokinesis
- cytoplasm divides
Cytokinesis: Animal VS Plant
Animal cells lack a cell wall so cytokinesis is accomplished by pinching the plasma membrane in half. At the midpoint of the cell, a cleavage furrow begins as a ring of microfilaments contracts and pinches the cell in two.
Plant cells have the hard cell wall that prevents such pinching. They divide by using vesicles
carrying cell wall material fusing together to form a cell plate between the two daughter cells that eventually becomes the new cell walls.
Role of checkpoints in the cell control system
Checkpoints are times during the cell cycle when the cell confirms that certain events have happened or materials made before moving into the next phase.
G1 or restriction check point, the cell decides to move ahead and commit to dividing or stay in the G0 non-dividing stage.
the end of G2 checkpoint to make sure the DNA and centrosomes have duplicated.
During mitosis, before cytokinesis occurs, the cell also checks to make sure the sister chromatids have properly separated so that the daughter cells have the correct chromosome number.
It is believed many different external and internal signals help control the cell control system.
Normal Cell VS cancerous cells in cell division
Normal cells:
- Density dependent inhibition: when conditions become too crowded, the cells stop dividing. - Anchorage dependence: preferring to be attached to a substrate in order to divide. - have a set number of times they can divide before they stop.
Cancer cells:
- lack this density dependent inhibition. - lack this anchorage dependence. - can divide an endless amount of time.
Difference between benign, malignent, and metastatic tumors
Any tumor is a mass of abnormal cells that are not exhibiting the normal cell control.
Benign tumor:
- stays in the original area and typically is not damaging unless it becomes very large and affects other organs’ function. - easily removed surgically.
Malignant tumor:
- invasive and spread beyond the original area.
- harder to remove surgically and other treatment options such as chemotherapy
and radiation are usually necessary.
Metastatic tumor:
- cancerous cells which leave the original tumor and travel through the body in the circulatory or lymphatic system and begin dividing in another part of the body, creating more tumors.
