biology chapter 2 Flashcards
cell division
is the process by which a cell doubles its organelles and cytoplasm, replicates its DNA, and then divides in two
unicellular organisms
cell division is a means of reproduction
multicellular organisms
is a method of growth, development, and replacement of worn-out cells
mitosis
is the division and distribution of the cell’s DNA to its two daughter cells such that each recieves a complete copy of the original genome
karyokinesis
nuclear division
cytokinesis
cell division
interphase
a period of growth and replication of genetic material prior to the initiation of mitosis
prophase
the chromosomes condense, and the centriole pairs separate and move towards the opposite poles of the cell. The spindle apparatus forms between them and the nuclear membrane dissolves, allowing the spindle fibers to interact with the chromosome
metaphase
the centriole pairs are now at opposite poles of the cell. The fiers of the spindle apparatus attach to each chromatid at the centromere to align the chromosomes at the center of the cell forming the metaphase plate
anaphase
the centromeres split so that each chromatid has its own distinct centromere, thus allowing sister chromatids to separate. The sister chromatids are pulled toward the opposite poles of the cell by the shortening of the spindle fibers.
telophase
the spindle apparatus disappears. A nuclear membrane forms around each set of newly formed chromosomes. Thus each nucleus contains the same number of chromosomes as the original or parent nucleus. The chromosomes uncoil, resuming their interphase form
cytokinesis
near the end of telophase, the cytoplasm divides into two daughter cells, each with a complete nucleus and its own set of organelles
cleavage furrow
in animal cells,. The cell membrane indents along the equator of the cell and finally inches through the cell, separating the two nuclei
plant cells
lack centrioles. The spindle apparatus is synthesized by microtubule organizing centers which are not visible. Are rigid and cannot form a cleavage furrow. They divide by the formation of a cell plate
cell plate
an expanding partition that grows outward from the interior of the cell until it reaches the cell membrane
meiosis
is the process by which these sex cells are produced. Produces the haploid (!N) number, halving the number of chromosomes. Involves two divisions of primary sex cells resulting in four haploid cells called gametes
interphase
the parent cell’s chromosomes are replicated during interphase resulting in the 2N number of sister chromatids
first meiotic division
the first division produces two intermediate daughter cells with N chromosomes with sister chromatids
prophase I
the chromatin condenses into chromosomes, the spindle apparatus forms, and the nucleoli and nuclear membrane disappear
synapsis
homologous chromosomes come toggether and intertwine
tetrad
each synaptic pair of homologous chromosomes contains four chromatids
crossing over
chromatids of homologous chromosomes break at corresponding points and exchange equivalent pieces of DNA
metaphase I
homologous pairs (tetrads) align at the equatorial plane, and each pair attaches to a separate spindle fiber by its kinetochore
anaphase I
the homologous pairs separate and are pulled to opposite poles of the cell