Chromosomes are threadlike structures inside each cell. They are made up of chromatin, a substance that contains protein and DNA, the cell's hereditary material. Cytoplasm is all the material inside the cell membrane except the nucleus. Cytoskeleton is a network of proteins that gives a cell its shape and moves structures in the cell cytoplasm. In some cells, the cytoskeleton helps the whole cell to move.
Endoplasmic reticulum is a complex network of membranes in the cytoplasm.
Enzymes are proteins that speed up chemical reactions. Genes are units of heredity that determine particular characteristics, such as height and hair color. Each gene is a section of a DNA molecule and carries instructions for making all or part of a specific protein. Meiosis is the process of division in the nucleus of some cells of the sex organs. It reduces the number of chromosomes in sex cells to half the number found in somatic cells.