Biology:

Cell Plate:

Plate that develops at the midpoint between the two groups of chromosomes in a dividing cell and that is involved in forming the wall between the two new daughter cells.

Diploid:

(of a cell or nucleus) containing two complete sets of chromosomes, one from each parent.

Haploid:

(of a cell or nucleus) having a single set of unpaired chromosomes.

S Phase:

S phase follows G1; its major function involves replicating the cell's DNA. The "S" name stands for synthesis. By using enzymes, the cell copies the DNA molecules of each chromosome. After S phase completes, chromosomes have two chromatids, meaning each chromosome has two molecules of DNA. This stage is not distinctly visible through a microscope because material inside the cell is too diffuse.

Ovaries:

A female reproductive organ in which ova or eggs are produced, present in humans and other vertebrates as a pair.

Tetrad:

A group of four chromatids formed by synapsis at the beginning of meiosis.

Gamete:

A mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote.

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.

Centromere:

A specialized structure on the chromosome, appearing during cell division as the constricted central region where the two chromatids are held together and form an X shape.

Chromosome:

A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

G2 Stage:

After S phase, a cell enters G2, or "Gap 2," and it involves another period of growth. The cell synthesizes more proteins, and organelles like mitochondria grow and divide. The cell also resumes normal functions like transforming food into fuel; cells stock up on this energy for its use in mitosis. G2 is the final step before a cell enters the first stage of mitosis.

Gonad:

An organ that produces gametes; a testis or ovary.

Somatic Cells:

Any cell of a living organism other than the reproductive cells.

Chromatid:

Each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.

Spindle Fibers:

Form a protein structure that divides the genetic material in a cell. The spindle is necessary to equally divide the chromosomes in a parental cell into two daughter cells during both types of nuclear division: mitosis and meiosis.

Homologous:

Having the same or a similar relation; corresponding, as in relative position or structure.

Know how DNA makes a chromosome:

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.

Asexual:

Independent of sexual processes, especially not involving the union of male and female germ cells.

G1 Stage:

Interphase begins with G1, which stands for "Gap 1." During G1, cells grow and synthesize proteins needed for mitosis. These proteins also activate the cell's metabolism and break down carbohydrates and lipids to transform this food into energy. Chromosomes inside the cell have not yet replicated in G1, so each chromosome contains only one DNA molecule.

Oogenesis:

Is the creation of an ovum (egg cell). It is the female form of gametogenesis; the male equivalent is spermatogenesis.

Cleavage Furrow:

Is the indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process of cell division.

Cytokinesis:

Is the physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells. It occurs concurrently with two types of nuclear division called mitosis and meiosis, which occur in animal cells.

Spermatogenesis:

Is the process in which spermatozoa are produced from male primordial germ cells by way of mitosis and meiosis.

Explain the differences between mitosis and meiosis:

Meiosis has two rounds of genetic separation and cellular division while mitosis only has one of each. In meiosis homologous chromosomes separate leading to daughter cells that are not genetically identical. In mitosis the daughter cells are identical to the parent as well as to each other.

Explain the benefits of mitosis:

Mitosis creates identical copies of the original cells. This allows our skin or our liver to be made of identical cells and allows plants to be able to mass produce leaves with identical properties. Imagine if every one of our skin cells had different DNA!

Zygote:

The cell produced by the union of two gametes, before it undergoes cleavage.

Centrosome:

The centrosome is an organelle that is the main place where cell microtubules get organized. They occur only in plant and animal cells. Also, it regulates the cell division cycle, the stages which lead up to cell division.

Karyotype:

The chromosomes of a cell, usually displayed as a systematized arrangement of chromosome pairs in descending order of size.

Ova:

The female reproductive cell or gamete of animals, which is capable of developing, usually only after fertilization, into a new individual.

Prophase:

The first and longest stage of mitosis. In this stage the chromosomes become visible and the centrioles separate and move to opposite poles of the cell.

Telophase:

The fourth and last stage of mitosis. During this stage the chromosomes gather at opposite ends of the cell and lose their distinct rod-like shapes. Two new nuclear membranes then form around each of the two regions of DNA and the spindle fibers disappear.

Testes:

The male gonad or reproductive gland, either of two oval glands located in the scrotum.

Chromatin:

The material of which the chromosomes of organisms other than bacteria (i.e., eukaryotes) are composed. It consists of protein, RNA, and DNA.

Kinetochore:

The place on either side of the centromere to which the spindle fibers are attached during cell division.

Mitosis:

The process in cell division by which the nucleus divides, typically consisting of four stages, prophase, metaphase, anaphase, and telophase, and normally resulting in two new nuclei, each of which contains a complete copy of the parental chromosomes.

Gametogenesis:

The process in which cells undergo meiosis to form gametes.

Cytokinesis:

The process that follows the last stage of mitosis. With two complete copies of the DNA now in two different regions of one cell, the cell membrane will pinch and divide the cytoplasm in half. The result is two individual cells that are identical to the original cell. Each of the two new cells have a complete copy of the DNA and contain all of the organelles that the original cell had.

Metaphase:

The second stage of mitosis. In this stage the chromosomes line up across the center of the cell and become connected to the spindle fiber at their centromere.

Anaphase:

The third stage of mitosis. In this stage the sister chromatids separate into individual chromosomes and are pulled apart.