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Biology today and tomorrow ch 8

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meiosis
Nuclear division process that halves the chromosome number. basis of sexual reproduction
mitosis
nuclear division mechanism that maintains the chromosome number. Basis of body growth,tissue repair and replacement in multicelled eukaryotes; also asexual reproduction in some plants, animals, fungi, and protists
cell cycle
a series of events from the times a cell forms until its cytoplasm divides
homogolous
refers to the two members of a pair of chromosomes with the same length, shape and genes
interphase
in a eukaryotic cell cycle, the interval between mitotic divisions when a cell grows, roughly doubles the number of its cytoplasmic components, and replicates its DNA
anaphase
stage of mitosis in which sister chromatids seperate andmove to opposite spindle poles
metaphase
stage of mitosis during which the cell's chromosomes align midway between the poles of the spindle
prophase
stage of mitosis in which chromosomes condense and become attatched to a newly froming spindle
spindle
dynamically assembled and disassembled array of microtublesthat moves chromosomes during nuclear division
telophase
stage of mitosis during which chromosomes arrice at the spindle poles and decondense, and new nuclei form
asexual reproduction
reproductive mode by which offspring arise from one parent and inheriet that one parents genes only
cell plate
after nuclear division in a plant cell, a disk shaped structure that forms a cross-wall between the two new nucllei
cleavage furrow
in a dividing animal cell, the indentation where cytoplasmic division will occur
clone
a genetically identical copy of an organism
contractile ring
a thin band of actin and myosin filaments that wraps around the midsection of an animal dell. During cytoplasmic division , the band contracts and pinches the cytoplasm in two
alleles
forms of a gene that encode slightly different versions of the genes product
fertilization
fusion of a sperm nucleus and an egg nucleus, the result being a single-celled zygote
gamete
mature, haploid reprosuctive cell
haploid
having one of each type of chromosome characteristic of the species
sexual reproduction
reproductive mode by which offspring arise from two parents and inherit genes from both.
zygote
cell formed by fusion of gamtes; first cell of a new individual
crossing over
process in which homologous chromosomes exchange corresponding segments during meiosis
egg
mature female gamete, or ovum
gametophyte
a haploid, multicelled body in which gametes form during the life cycle of plants
sperm
mature male gamete
sporophyte
diploid, spore-producing body of a plant