chromosome
in a eukaryotic cell, one of the structures in the nucleus that are made up of DNA and protein; in a prokaroytic cell, the main ring of DNA
histone
a type of protein molecule found in the chromosomes of eukaryotic cells but not prokaryotic cells
chromatid
one of the two strands of a chromosome that become visible during meiosis or mitosis
centromere
the region of the chromosome that hold the two sister chromatids together during mitosis
chromatin
the material that makes up both mitotic and interphase chromosomes; a complex of proteins and DNA strands that are loosely coiled such that translation and transcription can occur
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
a micrograph of the array of chromosomes visible in a cell during metaphase; a graphical display that shows an individual's chromosomes 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 has only 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
mitois
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 (gametes or spores)
gamete
a haploid reproductive cell that unites with another haploid reproductive cell to form a zygote
interphase
a period between two mitotic or meiotic divisions during which the cell grows, copies its DNA, and synthesizes protein
cytokinesis
the division of the cytoplasma of a cell; 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 and the dissolution of the nuclear envelope
spindle fiber
one of the microtubules that extend across a dividing eukaryotic cell; assists 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 separate
telophase
the final stage of mitosis and 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 into two
synapsis
the pairing of 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 during meiosis; 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 distribuation 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