Biology 8
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44 terms
Terms | Definitions |
|---|---|
 histones | help maintain the shape of the chromosome and aid in the tight packing of DNA |
| nonhistone | proteins that do not participate in packing of DNA, instead control the activity of specific regions of DNA |
| chromatid | one half of a chromosome, they form as DNA makes a copy of itself before cell division |
| centromere | the constricted area of a chromatid holds the two chromatids together until separation |
| sex chromosomes | chromosomes that determine the gender of an organism, carry genes for other characteristics as well |
| autosomes | the name of all of the chromosomes in any given organism |
| homologous chromosomes | two copies of a similar chromosome same size and shape and carry genes for same traits |
| karyotype | photomicrograph of chromosomes in a dividing cell found in a normal human |
| diploid | cells that have two sets of chromosomes, all chromosomes except for sex chromosomes |
| haploid | sex chromosomes, have half of the number of chromosomes that are present in diploid cells |
| binary fission | the division of a prokaryotic cell into spring cells |
| mitosis | occurs in the reproduction of unicellular organisms and creates genetic material identical to that of the original cell |
| meiosis | reduces the chromosome number in new cells, cells created by meiosis join together to create a cell with a full set of chromosomes |
| cell cycle | the repeating set of events that makes up the life of a cell |
| interphase | the time between cell divisions |
| M phase | or mitosis, the nucleus of a cell divides |
| cytokinesis | the division of the cytoplasm of the cell |
| G1 phase | offspring cells grow to mature size, the first step of interphase |
| S phase | cell's DNA is copied, happens after a cell has reached mature size |
| G2 phase | represents the time gap following DNA synthesis, or S phase, and the preceding cell division |
| G0 phase | an exiting of the cell cycle, usually occurring at the G1 phase, cells do not copy their DNA, and do not get ready for division |
| prophase | the first phase of mitosis, begins with the shortening and tight coiling of DNA into rod shaped chromosomes that can be seen with a light microscope, the nucleolus and the nuclear membrane break down and disappear |
| centrosomes | two pairs of dark spots next to teh disappearing nucleus each centrosome contains cylindrical bodies called centrioles, centrosomes move towards polar sides of the cell |
| centrioles | small cylindrical bodies, not in plant cells |
| spindle fibers | made of microtubules, radiate from the centrosomes in preparation for mitosis, pull apart chromosomes |
| mitotic spindle | array of spindle fibers in which the spindle fibers radiate from centrosomes |
| kinetochore fibers | extend from kinetochore of each chromatid to one centrosome |
| kinetochore | a disk shaped protein |
| polar fibers | extend across the dividing cell from one centrosome to another |
| metaphase | the second phase of mitosis, chromosomes are easier to identify when using a microscope kinetochore fibers move chromosomes to the equator of the dividing cell each chromosome is held in place by kinetochore fibers |
| anaphase | third stage of mitosis, chromatids of each chromosome separate at the centromere and slowly move, centromere first, toward the poles of the dividing cell |
| telophase | the fourth phase of mitosis, after chromosomes reach the poles of the cell, spindle fibers disassemble and chromosomes return to a less tightly coiled chromatin state, nuclear envelope forms around each set of chromosomes and nucleolus forms in each of the new forming cells |
| cleavage furrow | the area of the cell membrane tht pinches in and eventually separates the dividing cell into two cells, does so through microfilaments |
| cell plate | vesicle formed by the golgi apparatus fuse at the midline of the dividing cell, forming a membrane bound cell wall, when complete it separates the cell into two cells |
| gametes | in humans, sperm cells and egg cells, or 1n |
| synapsis | the pairing of homologous chromosomes, does not occur in mitosis |
| tetrad | each pair of homologous chromosomes |
| genetic recombination | a production of a new mixture of genetic material |
| independent assortment | the random separation of the homologous chromosomes |
| spermatids | a diploid reproductive cells divides meiotically and produces four haploid cells called.... |
| spermatogenesis | the production of sperm |
| polar bodies | the smaller counterparts to the creation of an egg cell |
| asexual reproduction | the production of offspring from one parent |
| sexual reproduction | the production of offspring through meiosis and the union of a sperm and an egg |
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