Cell Division And The Cell Cycle Flashcards
Give a brief overview of the cell cycle.
During the cell cycle, there is a duplication of cellular components followed by partition into two daughter cells at cell division.
The S phase is characterised by DNA synthesis, and the M phase by mitosis. These phases are separated by the G, or gap, phases.
What are the phases of the mitotic cell cycle?
G1>S phase>G2>M phase
What happens in G1 phase?
In the G1 phase, biosynthetic activities increase, with protein and RNA synthesis.
What happens during S phase?
In the S phase, DNA synthesis begins, with the S phase ending when the DNA content of the nucleus is doubled and the chromosomes have replicated (i.e. Each chromosome now consists of two identical sister chromatids).
What is G2 phase?
It is a rest phase after the S phase.
What happens in M phase?
In the M phase (mitosis), replicated chromosomes condense, nuclear membrane breaks down, and the sister chromatids separate. Two new nuclei are formed, and the cytoplasm divides (cytokinesis) to generate two daughter cells.
What stages of the cell cycle make up interphase?
G1, S, G2 are collectively known as the interphase stage of the cell cycle.
Define mitosis.
Mitosis is a process of cell division which results in the production of two daughter cells from a single parent. The daughter cells are identical to one another and the original parent cell.
List the 4 principle stages of mitosis.
Prophase, Metaphase, Anaphase, Telophase
Describe prophase of mitosis.
During prophase the chromatin (which is diffuse in interphase) condenses into chromosomes. Each chromosome has duplicated and now consists of two sister chromatids. At the end of prophase, the nuclear envelope breaks down into vesicles.
Describe what happens during metaphase of mitosis.
The chromosomes align at the equatorial plate and are held in place by microtubules attached to the mitotic spindle and to part of the centromere.
What happens during anaphase of mitosis?
The centromeres divide. Sister chromatids separate and move toward the corresponding poles.
What happens during telophase of mitosis?
During telophase of mitosis daughter chromosomes arrive at the poles and the microtubules disappear. The condensed chromatin expands and the nuclear envelope reappears. The cytoplasm divides, the cell membrane pinches inward ultimately producing two daughter cells (cytokinesis).
What is meiosis?
Meiosis is the type of cell division by which germ cells (eggs and sperm) are produced, and involves a reduction in the amount of genetic material. This is achieved by two successive nuclear divisions with on,y one round of DNA replication.
Describe the stages of meiosis.
Interphase - before meiosis begins, genetic material is duplicated.
First Division:
Prophase 1 - duplicated chromatin condenses. Each chromosome consists of two, closely associated sister chromatids. Crossing over can occur during the latter part of this stage.
Metaphase 1 - homologous chromosomes align at the equatorial plate.
Anaphase 1 - homologous pairs separate with sister chromatids remaining together.
Telophase 1 - two daughter cells are formed with each daughter containing only one chromosome of the homologous pair.
Second division of meiosis: Gamete formation
Telophase 2 - cell division is complete. Four haploid daughter cells are obtained. One parent cell produces four daughter cells. Daughter cells have half the number of chromosomes found in the original parent cell and with crossing over, are genetically different.
