USF BSC 2210: Cell Cycle - Mitosis and Meiosis

Anaphase

As kinetochore microtubules begin to contract, the chromosomes are broken apart at the centromeres, causing the chromatids to move to opposite poles. Polar microtubules elongate, in turn elongating the cell. The cleavage furrow is formed, setting the stage for cytokinesis. The centrosomes begin to move further apart as they pull the chromatids with them to their respective poles.

Aster

A radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis.

Centromere

A region on a chromosome that attaches either the two arms of a chromosome, or two sister chromatids together.

Centrosome

A structure in animal cells containing centrioles from which the spindle fibers develop. Two centrioles are present per centrosome.

Kinetochore

A structure made up of proteins that have assembled on specific sections of DNA at each centromere. Kinetochore microtubules attach to this to allow the sister chromatids to be separated.

Anaphase I

As kinetochore microtubules begin to contract, the tetrads are broken apart, causing the homologous chromosomes to move to opposite poles. Polar microtubules elongate, in turn elongating the cell. Centrosomes begin to move further apart as they pull the chromatids with them.

Independent Assortment

Because each pair of homologous chromosomes is positioned independently of the other pairs at metaphase I, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair.

Prophase I

Chromosomes begin to condense. Homologous chromosomes pair up, form chiasmata, and exchange genetic material via crossing over. This is one of the ways cells obtain such genetic diversity in gametes.

Mitosis

Eukaryotic cell division during which a parent cell divides into two daughter cells that are genetically identical to the parent cell.

Meiosis

Eukaryotic cell process during which a parent cell divides into four gametes that are genetically diverse from the parent cell and from each other.

Metaphase Plate

Plane midway between the two poles of the cell where chromosomes line up during metaphase.

Crossing Over

Process in which homologous chromosomes exchange portions of their chromatids during meiosis.

G1 Phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.

Cyclin

A cellular protein that occurs in a cyclically fluctuating concentration and that plays an important role in regulating the cell cycle.

Centrioles

A minute cylindrical organelle near the nucleus in animal cells, occurring in pairs and involved in the development of spindle fibers in cell division.

G0 Phase

A nondividing state occupied by cells that have left the cell cycle, sometimes reversibly.

Anaphase II

As kinetochore microtubules begin to contract, the chromosomes are broken apart at the centromeres, causing the chromatids to move to opposite poles. Polar microtubules elongate, in turn elongating the cell. Centrosomes begin to move further apart as they pull the chromatids with them.

Prophase

Chromosomes begin to condense. The Nuclear Envelope breaks down, releasing the chromosomes. The mitotic spindle begins to form, as the centrioles form aster structures around them at opposite ends of the cell. This spindle is made up of microtubules and is meant to attach to the chromosomes at the kinetochores and line them up correctly.

Cyclin-Dependent Kinase (Cdk)

One of a group of enzymes associated with cyclins that help them perform their functions.

Chromatid

One of two identical "sister" parts of a duplicated chromosome

Metaphase II

The chromosomes, now bound to kinetochore microtubules, are lined up at the metaphase plate. Because of crossing over in meiosis I, the two sister chromatids of each chromosome are not genetically identical. In Meiosis II, the chromosomes are lined up with one chromatid facing each end of the cell, similarly to Metaphase in Mitosis.

Metaphase I

The chromosomes, now bound to kinetochore microtubules, are lined up at the metaphase plate. Each pair has lined up independently of other pairs, which is known as independent assortment. In Meiosis I, pairs of homologous chromosomes are lined up with the homologous chromosomes facing each end of the cell, meaning that when they are separated, each daughter cell will gain one of each homologous chromosome rather than one chromatid as in Mitosis.

Metaphase

The chromosomes, now bound to kinetochore microtubules, are lined up at the metaphase plate. In Mitosis, the chromosomes are lined up in a straight line, with one chromatid facing each end of the cell. Note: Metaphase II during Meiosis II looks very similar to Metaphase in Mitosis, and functions similarly as well.

Prophase II

The first phase of meiosis II. Prophase II is identical to mitotic prophase, except that the number of chromosomes was reduced by half during meiosis I.

Telophase II

The mitotic spindle is broken down, and the chromosomes are released. Two nuclei are formed in each cell, as the chromosomes are surrounded by the reconstituting nuclear membrane on both sides of the dividing cell. The four daughter cells are genetically distinct from one another and from the parent cell.

Telophase

The mitotic spindle is broken down, and the chromosomes are released. Two nuclei are formed, as the chromosomes are surrounded by the reconstituting nuclear membrane on both sides of the dividing cell. Chromosomes begin to unfold back into their decondensed state.

Telophase I

The mitotic spindle is broken down, and the chromosomes are released. When telophase I begins, each half of the cell has a complete haploid set of duplicated chromosomes. Each chromosome is composed of two sister chromatids; one or both chromatids include regions of non-sister chromatid DNA. Two nuclei are formed, as the chromosomes are surrounded by the reconstituting nuclear membrane on both sides of the dividing cell.

Interphase

The resting phase between successive mitotic divisions of a cell, or between the first and second divisions of meiosis.

G2 Phase

The second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occurs.

S Phase

The synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated.

Homologous Chromosomes

The two chromosomes of a pair have the same length, centromere position, and staining pattern

Prometaphase I

The Nuclear Envelope breaks down, releasing the chromosomes. The mitotic spindle begins to form, as the centrioles form aster structures around them at opposite ends of the cell.

Chromosome

Usually linear bodies in the cell nucleus that contain the genetic material.

Cleavage Furrow

The area of the animal cell membrane that pinches in and eventually separates the dividing cell.

Cytokinesis I

The cell contracts in the middle, as the cell is cleaved into two daughter cells that are genetically diverse from each other and their parent cell. These daughter cells are still diploid (2n), but the chromosomes are still duplicated.

Cytokinesis

The cell contracts in the middle, as the cell is cleaved into two daughter cells that are genetically identical to each other and to the parent cell. Cytokinesis functions similarly in Meiosis I and Meiosis II, but a key thing to note is the number of cells produced at the end of each process, and the genetic makeup of those cells as well.

Chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones.