Term | Definition |
chromosome | rod-shaped structure made of DNA and protein |
histone | a type of protein molecule found in the chromosomes of only eukaryotic cells |
chromatid | one of the two strands of a chromosome that become visible during meiosis or mitosis |
centromere | the region of the chromosome that holds the two sister chromatids together during mitosis |
chromatin | the substance that composes eukaryotic chromosomes; it consists of specific proteins, DNA, and small amounts of RNA |
sex chromosome | one of the pair of chromosomes that determine the sex of an individual |
autosome | any chromosome that is not a sex chromosome |
homologous chromosome | chromosomes that have the same sequence of genes, that have the same structure, and that pair during meiosis |
karyotype | an array of the chromosomes found in an individual's cells at metaphase of mitosis and arranged in homologous pairs and in order of diminishing size |
diploid | a cell that contains two haploid sets of chromosomes |
haploid | describes a cell, nucleus, or organism that only has one set of unpaired chromosomes |
binary fission | a form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size |
mitosis | in eukaryotic cells, a process of cell division that forms two new nuclei, each of which has the same number of chromosomes |
asexual reproduction | reproduction that does not involve the union of gametes and in which a single parent produces offspring that are genetically identical to the parent |
meiosis | a process in cell division during which the number of chromosomes decreases to half the original number by two divisions of the nucleus, which results in the production of sex cells |
gamete | a haploid reproductive cell that unites with another haploid reproductive cell to form a zygote |
interphase | the period of the cell cycle during which activities such as cell growth and protein synthesis occur without visible signs of cell division |
cytokinesis | the division of the cytoplasm of a cell; cytokineses follows the division of the cell's nucleus by mitosis or meiosis |
prophase | the first stage of mitosis and meiosis in cell division; characterized by the condensation of the chromosomes |
spindle fiber | one of the microtubules that extend across a dividing eukaryotic cell; assist in the movement of chromosomes |
metaphase | one of the stages of mitosis and meiosis, during which all of the chromosomes move to the cell's equator |
anaphase | a phase of mitosis and meiosis in which the chromosomes seperate |
telophase | the final stage of mitosis or meiosis, during which a nuclear membrane forms around each set of new chromosomes |
cell plate | the precursor of a new plant cell wall that forms during cell division and divides a cell in two |
synapsis | the pairing of homologous chromosomes during meiosis |
tetrad | the four chromatids in a pair of homologous chromosomes that come together as a result of synapsis during meiosis |
crossing-over | the exchange of genetic material between homologous chromosomes; can result in genetic recombination |
genetic recombination | the regrouping of genes in an offspring that results in a genetic makeup that is different from that of the parents |
independent assortment | the random distribution of the pairs of genes on different chromosomes to the gametes |
spermatogenesis | the process by which male gametes form |
oogenesis | the production, growth, and maturation of an egg, or ovum |
polar body | a short-lived product of the formation of gametes by meiosis |
sexual reproduction | reproduction in which gametes from two parents unite |