CELL DIVISION AND REPRODUCTION

haploid

having a single, complete set of chromosomes, or one half of each pair of homologous chromosomes

diploid

having chromosomes in homologous pairs

homologous pair

pair of identical chromosomes (chromosomes that contain the same genes) from each parent, which all organisms produced by sexual reproduction receive

interphase

period between two periods of mitosis

prophase I

the stage in the first meiotic division in which the doubled chromosomes become visible and the nuclear membrane disappears

crossing over

a condition in which non-sister chromatids of homologous chromosomes exchange genes

M phase

a period in the life of the cell when it is conducting cell division

tetrad

during prophase I, when the two pairs of chromatids of the homologous pair of chromosomes come together to form a four chromatid unit; time when crossing-over can occur

synapsis

the meiotic process in prophase I in which the tetrads line up side-by-side; initiates the crossing over process

meiosis

the process involving the division of the nucleus in a reproductive cell; cell division in which the daughter cells have fewer chromosomes than the parent cell; responsible for genetic recombination

metaphase I

the stage in the first meiotic division in which the homologous chromosomes line up as a pair, forming a tetrad of chromatids at the equator of the cell

anaphase II

the stage in the second meiotic division in which sister chromatids of a chromosome split and migrate to opposite poles

prophase II

the stage in the second meiotic division in which the chromatid pair becomes visible and the nuclear membrane disappears

metaphase II

the stage in the second meiotic division in which the chromatid pair lines up at the equator of the cell

telophase I

the stage of the first meiotic division when the cell divides into two cells, each containing one member of each pair of homologous chromosomes

telophase II

the stage of the second meiotic division when the cell divides into two haploid cells that become the gametes

anaphase I

the stage on the first meiotic division in which sister chromatids of a chromosome split and migrate to opposite poles