Biology
Chapter 9
MITOSIS
OVER ARCHING CONCEPTS:
CONCEPTS
in eukaryotic DNA coils into chromosomes only during mitosis and meiosis.
1.
THE CELL CYCLE series of events from one cell division
to the next. Interphase, mitosis,
and
cytoplasmic cytoplasmic division constitute one turn of the cell cycle. It is the cycle from mitosis to mitosis.
2. INTERPHASE period of cell growth and development that precedes mitosis and follows cytokinesis. Cell increases in mass, doubling its cytoplasmic components, and duplicates its DNA (12 to 24 hrs.)
A. G1 interval of cell growth before DNA replication (chromosomes unduplicated). Most of proteins, RNA, carbohydrates, and lipids are made in the G1 interval. Cell doubles in size along with most organelles.
B. S time of synthesis, DNA replication is completed (chromosome duplication). DNA in the chromatin replicates.
C.
G2 second interval after DNA replication, when the cell
prepares for division. Period of
rapid growth when necessary enzymes are synthesized.
3. MITOSIS nuclear division mechanism that keeps chromosome numbers constant. It is the division of the cell nucleus in which chromosomes in the parent cell divide into two identical sets. Cell growth and protein synthesis stop. Mitosis takes 1 to 2 hours.
A. Prophase first phase of mitosis, the beginning of chromosomal condensing to nuclear break up.
a. early prophase duplicated chromosomes begin to condense. Centrioles are located at one end (pole) of the cell.
b.
late prophase new microtubules become assembled and they move
the two pairs of centrioles to the opposite poles of the cell.
The nucleus also starts to break apart. Chromosomes continue to condense.
Asters form.
B. Prometaphase - nuclear envelop is broken up completely. Microtubules penetrate nuclear area and spindle microtubules attached to the sister chromotids of each chromosome
a. Metaphase second stage of mitosis, at this stage chromosomes are the most condensed. Microtubule spindles have pulled chromosomes to the center of the cell called the metaphase plate.
D. Anaphase third stage of mitosis when sister chromatids of each chromosome separate from each other and move to opposite poles
E.
Telophase final phase of mitosis, after chromosomes arrive at
the spindle poles they decondense and
patches of new membrane fuse to form new nuclear membranes.
Once two nuclei form, telophase is over!
4. CYTOKINESIS
partitioning of the parent cell into two separate daughter cells each
with one
nucleus. Occurs after telophase.
5. CHROMOSOME NUMBER the sum of all chromosomes in cells of a given type
6. CHROMOSOME a duplicated or unduplicated DNA molecule. Each chromosome consists of two identical parts called a chromatid. In prokaryotes it is a circular DNA molecule. Long, stringy aggregate of genes that carry heredity information and are formed from condensed chromatin.
7. CHROMATIN Mass of genetic material composed of DNA and proteins that condense around a histone to form chromosomes in a nucleus. Uncoiled DNA along with histones.
8. HISTONES groups of special protein molecules, which DNA wrap around to form chromosomes
9. CHROMOTID - Each of a pair of identical DNA molecules after DNA replication, joined at the centromere. A chromatid is one-half of a replicated chromosome. Once separated they become a chromosome.
10. HOMOLOGOUS CHROMOSOMES in all sexually reproducing organisms chromosomes occur impairs. The two members of each pair are called homologous chromosomes. Each chromosome of a pair has the same size and shape as its homologue.
11. HOMOLOG one partner of the pair in a homologous chromosome.
12. CENTROMERES The 'anchor points' that control the separation of chromosomes when cells divide. Each normal human chromosome has a single centromere, which appears as a constriction under a microscope. The centromere can be near the middle of a chromosome or near one end of it. It partitions the chromosome into long or short arms. It is the point at which each pair of chromatids is attached. The centromere is where mitotic spindles attach to pull homologous chromosomes apart during mitosis.
13. DIPLOID NUMBER two of each type of chromosome (2n). A diploid cellcontains both chromosomes of a homologous pair.
14. HAPLOID a cell that has only one chromosome of each homologous pair in it (1n).
15. SPINDLE composed of two sets of microtubules extending from its two poles
16. ACTIN protein which rings the center of the cell during cytokinesis and begins to pinch the cell into two daughter cells.
17. KINETOCHORDS Structures forming at centromeres during Mitosis for binding microtubules.
20. CELL PLATE FORMATION in plant cells instead of cytoplasmic division (cleavage furrow) cell plate forms forming a new cell wall dividing the parent cell into two daughter cells.
21. CENTRIOLES in animal cells, the two dark spots that form after the nucleus breaks downnduring prophases. They move away from each towards opposite poles of the cell.
22. POLAR FIBERS spindle fibers that that extend across the cell from centriole to centriole (pole to pole).
23. KINETOCHORE spindle fibers that that extend from centromeres of a chromosome to the centrioles.
24. ASTERS
protein fibers that radiate from each centriole. Asters are not found in plant cells.
25. TELOMERE
26. CHROMOSOME ARMS There are two "arms" to each chromosome, called p and q, which are defined by a central pinched section called the centromere.
27. LOCUS The locus is the position of a gene on a chromosome