Chapter 9 AP Biology Mitosis and the Cell Cycle

Cell Division

Reproduction of cells.

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How many Chromatids exist from prophase-anaphase in normal human somatic cells.

none; now called chromosomes

How many sister chromatids exist in late anaphase-telophase in normal human somatic cells.

Cell Cycle

An ordered sequence of events in the life of a cell from its origin in the division of a parent cell until its own division of a parent cell until its own division into 2. The eukaryotic cells cycle is composed of interphase (including G1, S, and G2 subphases) and M phase (including mitosis and cytokinesis)

Genome

The genetic material of an organism or virus; the complete complement of an organism’s genes along with its noncoding nucleic acid sequences. A cells genetic information.

Chromosomes

A cellular structure consisting of DNA wrapped around histones which has been condensed. A eukaryotic cell typically has multiple linear __________ located in the nucleus. A prokaryotic cells typically has one circular chromosomes in the nucleoid. These condense and form in eukaryotic cells during mitosis.

Chromatin

The complex of DNA and proteins that males up eukaryotic chromosomes. When the cell is not dividing DNA exists in this non condensed form. In long thin strands not visible to light microscope.

Somatic Cells

All body cells except reproductive cells which have 2 sets of chromosomes.

Gametes

Reproductive cells: sperm and eggs. They are haploid and have only 1 set of chromosomes.

Sister Chromatids

Joined identical copies of the original chromosome. They are attached in duplicated chromosomes by sister chromatid cohesion.

Cohesins

Protein complexes which attach sister chromatids until anaphase.

Sister Chromatid Cohesion

The attachment of sister chromatids by cohesions.

Centromere

A region of chromosomal DNA where the chromatid is attached most closely to its sister chromatid.

Arms

Part of chromatid to either side of the centromere.

Mitosis

A process of nuclear division in eukaryotes cell conventionally divided into five stages; prophase, prometaphase, metaphase, anaphase, and telophase. Mitosis conserves chromosome number by allocating replicated chromosomes equally to each of the daughter nuclei. 2n-2n, 1 division, cells are genetically identical, done for growth or repair.

Cytokinesis

The division of the cytoplasm

Mitotic (M) Phase

The phase of the cell cycle that includes mitosis and cytokinesis.

Interphase

The much longer stage of the cell cycle (90%) which can be broken into three subphases. The period in the cell cycle when the cell is not dividing. During interphase, cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. Interphase often accounts for about 90% of the cell cycle.

G1 phase

The first gap phase or the first growth phase of the cell cycle consisting of the portion of interphase before DNA synthesis. Time in which the cell grows and carries out it normal cellular functions.

S phase

THe synthesis phase of interphase where DNA is replicated.

G2 Phase

The second gap phase or the second growth phase where the cell continues to grow and prepare for mitosis.

G2 of Interphase

Which phase: A nuclear envelope encloses the nucleus, nucleoli are present, a second centrosome forms, DNA not condensed.

Prophase

Which phase: Chromatin fibers condense into chromosomes, the nucleoli disappear, sister chromatids joined by cohesion, mitotic spindle begins to form, centrosomes move away from each other.

Prometaphase

Which phase: nuclear envelope fragments, the microtubules extend from each centrosome attach to the chromosome at the kinetochore, each chromatid has a kinetochore, nonkinetochore microtubules interact with those of opposite pole.

Metaphase

Which phase: The centrosome are now a t opposite poles of the cell and the mitotic spindle is complete, chromosomes are arranged along the metaphase plate. Chromosomes attached to kinetochore microtubules of both poles.

Anaphase

Which phase: the shortest stage of mitosis, cohesion proteins are cleaved and the sister chromatids are split and pulled to opposite sides of the cell. The nonkinetochore microtubules push past each other and cause the cell to elongate. By the end each end of the cell has 2 sets of chromosomes.

Telophase

Which phase: two daughter nuclei form in the cell, nuclear envelope reforms from fragments, nucleoli reappear, chromosomes decondense, microtubules depolymerized.

Cytokinesis

Which phase: The division of the cytoplasm, begins in telophase

Mitotic Spindle

An assemblage of microtubules and associated proteins that is involved in the movement of chromosomes during mitosis. Includes the centrosome, kinetochore and nonkinetochore microtubule, and the aster.

Centrosome

A subcellular region present in the cytoplasm of animal cells that functions as a microtubule-organizing center and is important during cell division. It contains two centrioles.

Aster

A radial array of short microtubules which extends from each centrosome.

Kinetochore

A structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle. Motor proteins within this structure are responsible for moving chromosomes towards the poles as the microtubules are disassembled.

Metaphase Plate

An imaginary plane equidistant from the poles of the cell.

Separase

An enzyme which cleaves the cohesions holding sister chromatids together.

Cleavage

The process of cytokinesis in animal cells characterized by the pinching of the plasma membrane due to a ring of actin filaments or microfilaments.

Cleavage Furrow

A shallow groove in the cell surface caused by the pinching of cell membranes.

Cell Plate

A membrane-bounded, flattened sac located at the midline of a dividing plant cells, inside which the new cell wall forms during cytokinesis. Eventually fuses with the plasma membrane.

Binary Fission

A method of asexual reproduction in single-celled organisms in which the cell grows to roughly double its size and the divides into two cells. Prokaryotes: no mitosis Unicellular Eukaryotes: Mitosis

Origin of Replication

The site where the replication of a DNA molecules begins in binary fission consisting of a specific sequence of nucleotides. The two origins then separate to opposite poles of the cell.

Dinoflagellates, Diatoms, and some yeasts

Unicellular eukaryotes that undergo mitosis yet the nuclear envelope remains intact.

Cytoplasm

Are the signals that regulate the cell cycle in the cytoplasm or the nucleus?

Cell cycle control system

A cyclically operating set of molecules in the eukaryotic cell that both trigger and coordinates key events in the cell cycle.

Checkpoint

A control point where stop and go-ahead signals can regulate the cycle. Major ________ are located in G1, G2, and mitosis.

G1 Checkpoint

THis checkpoint checks for cell size, growth factors, and environmental factors, and once these factors have been meet it allows the cell to proceed to the synthesis phase.

G2 checkpoint

This checkpoint checks that DNA has been completely replicated, that DNA damage and mutations didn’t occur, and that cell size is satisfactory to divide before allowing the cell to proceed to mitosis.

M Checkpoint

This check point makes sure that all of the spindle fibers are properly attached to chromosomes before allowing the cell to proceed to anaphase.

G0 Phase

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly. Most body cells are in this state and cells like nerve and muscle cells never divide. Occurs when the cell isn’t receiving the proper nutrients or growth factors

Cyclins

Proteins that activate cycling dependent kinases therefore regulating the cell cycle.

Cyclin Dependent Kinases

A family of protein kinases that play a crucial role in regulating the cell cycle. They are activated when they bind to specific proteins called cyclins. Once activated, CDKs phosphorylate target proteins that are necessary for the progression of the cell cycle, thus influencing events such as DNA replication, mitosis, and cytokinesis. Different cyclin-CDK complexes are active during different phases of the cell cycle, ensuring that the cell cycle progresses in an orderly manner.

Mitosis Promoting Factor

AKA Maturation Promoting Factor: a cdk bound to its m-cyclin partner. It triggers mitosis, aids in breaking down the nuclear envelope and promoting chromosome condensation.

Growth Factor

A protein released by certain cells that stimulates other cells to divide. Different cells react differently to these. It must be present in the extracellular environment for the growth and normal development of certain types of cells.

Platelet Derived Growth Factor

A growth factor made by platelets which stimulates the division of fibroblasts.

Density-dependent inhibition

THe phenomenon observed in normal animals cells that causes them to stop dividing when they come into contact with each other. Caused because the binding of cell-surface proteins sends a signal to both cells that inhibits cell division preventing the cells from moving forward in the cell cycle.

Anchorage Dependence

The requirement that a cell must be attached to a substratum (e.g. extracellular matrix or glass beaker) in order to initiate cell division. Caused by signals from plasma membrane proteins and elements of the cytoskeleton.

Cancer

When cells defy normal external factors (ignore density-dependent inhibition, and anchorage dependence, and create their own or bypass the need for growth factors) and internal factors (abnormal cell cycle) and bypass checkpoints in the cell cycle causing them to grow continuously or abnormally. Often caused by mutations. Causes tumors and often leads to death. Can sometimes be treated by radiation or chemotherapy. Cells that are _________ous often have abnormal numbers of chromosomes and their chromosomes have abnormalities like transformations, duplications, or deletions.

Transformation

THe process by which a cell in a culture acquires the ability to divide indefinitely, like the division of cancer cells.

Apoptosis

Programmed cell death when an error occurs or when the cell wears down. Cancer cells defy this event and continue to divide.

Benign Tumor

A mass of abnormal cells with specific genetic and cellular changes such that the cells are not capable of surviving at a new site and generally remain at the site of the tumor’s origin. Most do not causes serious issues and can be removed by surgery.

Malignant Tumor

A cancerous tumor containing cells that have significant genetic and cellular changes and are capable of invading and surviving in new sites. Can impair the functions of one or more organs and lead to death.

Metastasis

THe spread of cancer cells to locations distant from their original site typically via blood or lymph vessels.

Angiogenesis

The tendency of cancerous tumors to cause blood vessels to grow towards the tumor to supply the cancerous cells with nutrients.