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what does mitosis produce?
two genetically identical cells and it preserves the chromosome number--2n
what does meiosis produce?
occurs in sexually reproducing organisms and results in cells with half the chromosome number of the parent cell (n)
What does a chromosome consist of?
a highly coiled and condensed strand of DNA, a replicated one consists of two sister chromatids, where one is an exact copy of the other
what is a kinetochore?
Structure of proteins of each sister chromatid located at the centromere that links to the microtubules of centrosomes
what is the mitotic spindle?
Structure consisting mainly of microtubules that provides the framework for chromosome movement during cell division.
what two factors limit cell size and promote cell division?
-ratio of the volume of a cell to the surface area
-capacity of the nucleus to control the entire cell
how does the ratio of cell volume to surface area affect cell division?
the area of the cell membrane increases as the square of the radius, while the volume of the cell increases as the cube of the radius. As a cell grows larger, the volume inside of it increases at a faster rate than the cell membrane
how does the capacity of the nucleus affect cell division?
many cells need to have more than one nucleus
what are the five major phases of the cell cycle?
which together make up interphase
what is interphase?
the longest stage of the cell cycle
G1-period of intense growth and biochemical activity
S-synthesis/replication of DNA
G2-cell continues to grow and prepare for the next phase
cells spend 90% of life in interphase
what happens in prophase?
chromatin continues to condense into chromosomes, centrioles separate, spindle fibers form, nuclear envelope breaks down, nucleolus disappears
what happens in metaphase?
Sister chromatids are pulled by motor proteins along the spindle apparatus toward the center of the cell-then they line up along the middle or "equator"
what happens in anaphase?
The centromeres split. The two chromatids separate. The two seperate chromatids move along the spindle fibers to the opposite ends of the cell. The cell becomes stretched out as the opposite ends pull apart.
what happens in telophase?
chromosomes arrive at poles of sprindle apparatus, then they decondense, then the Nuclear membrane and nucleolus reform
how are cancer cells different from normal cells?
they do not have contact inhibition or density-dependent inhibition and keep reproducing and can metastasize in other regions of the body
what is meiosis?
form of cell division that produces gametes with the haploid chromosome number (n) and has two parts meiosis 1 and meiosis 2, which is the same as mitosis
what is crossing over?
the exchange of genetic material between non-sister chromatids of a tetrad during meiosis 1
what happens in meiosis 1?
Begins with a diploid cell that divides (homologous chromosomes separate) and produces two haploid cells with 1/2 of the number of chromosomes (sister chromatids are still together) as the parent cell
what happens in meiosis 2?
(Similar to mitosis) Cells divide again, sister chromatids separate and each cell produces 2 more new cells, different from the parent cell
what is spermatogenesis?
The production of sperm occuring in seminiferous tubules. Spermatogonia undergo mitosis to produce 4 haploid sperms of equal size.
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