Cell Cycles, Mitosis
P. 161-162, 164-177
8.1 The Cycle of Cell Growth and Division: An Overview
- In mitotic cell division, DNA replication is followed by the equal separation - that is,
segregation - of the replicated DNA molecules and their delivery to the daughter cells.
- The process ensures that the two cell products of a division have the same genetic
information as the parent cell entering division.
- Mitosis is the basis for growth and maintenance of body mass in multi-celled
eukaryotes and for the reproduction of many single celled eukaryotes.
- The chromosomes of eukaryotic cells are individual, linear DNA molecules with
- DNA replication and the duplication of chromosomal proteins convert each
chromosome into a structure composed of two exact copies known as sister
8.2 The Cell Cycle in Prokaryotic Organisms:
- Prokaryotic cells undergo a cycle of binary ﬁssion involving coordinated cytoplasmic
growth, DNA replication and cell division, producing two daughter cells from an original
- Replication of the bacterial chromosome consumes most of the time in the cell cycle
and begins at a single site called the origin, through reactions catalyzed by enzymes
located in the middle of the cell.
- Once the origin of replication is duplicated, the two origins actively migrate to the two
ends of the cell.
- Division of the cytoplasm then occurs through a partition of cell wall material that
grows inward until the cell is separated into two parts.
8.3 Mitosis and The Eukaryotic Cell Cycle:
- Mitosis and interphase constitute the mitotic cell cycle.
- Mitosis occurs in 5 stages.
1) In prophase, (stage 1) the chromosomes condense into short rods and the spindle
forms in the cytoplasm.
2) In prometaphase, (stage 2) the nuclear envelope breaks down the spindle, enters
the former nuclear area, and the sister chromatids of each chromosome make
connections to opposite spindle poles. Each chromatid has a kinetochore that attaches
to spindle microtubules.
3) In metaphase, (stage 3), the spindle is fully formed and the chromosomes, moved
by the spindle m