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
disjunction
each chromosome of paternal origin separates (or disjoins) from its homologue of maternal origin, and either chromosome can end up in either daughter cell
telophase I
a nuclear membrane forms around each new nucleus. At this point, each chromosome still consists of sister chromatids joined at the centromere
second meiotic division
the chromosomes aligh at the equator, separate and move to opposite poles, and are surrounded by a reformed nuclear membrane
asexual reproduction
is the production of offspring without fertilization
fission
binary fission is a simple form of asexual reproduction seen in prokaryotic organisms. The DNA replicates and a new plasma membrane and cell wall grow inward along the midline of the cell, dividing it into two equally sized cells with equal amounts of cytoplasm, each containing a duplicate of the parent chromosome
budding
is the replication of the nucleus followed by unequal cytokinesis. The cell membrane pinches inward to form a new cell that is smaller in size but genetically identical to the parent cell, and which subsequently grows to adult size. The new cell may separate immediately from the parent or it may remain attached to it, develop as an outgrowth, and seaparate at a later stage
regeneration
is the regrowth of a lost or injured body part. Replacement of cells occurs by mitosis
parthenogenesis
is the development of an unfertilized egg into an adult organism. This process occurs naturally in certain lower organisms
spore formation
all plants exhibit alternation of generations in which a diploid generation is succeeded by a haploid generation. The diploid sporphyte generation produces haploid spores which develop into the haploid gametophyte generation
vegetative propagation
undifferentiated tissues in plants, called meristems, provide a source of cells that can develop into an adult plant. Can occur naturally, or through human intervention. Is advantageous because it introduces no genetic variation and is a rapid form of reproduction