4.1.2.2 Mitosis and the Cell Cycle Flashcards
How do cells divide?
In a series of stages called the cell cycle
What happens during the cell cycle?
- During the cell cycle genetic material is doubled and then divided into two identical cells
What needs to happen before a cell can divide?
- Before a cell can divide it needs to grow and increase the number of sub-cellular structure such as ribosomes and mitochondria
- The DNA replicates to form two copies of each chromosome
What happens at the end of the cell cycle after mitosis?
Finally, the cytoplasm and cell membranes divide to form two identical cells
What is cell division by mitosis important in?
- The growth and development of tissues in multicellular organisms
- Repair of tissues in multi-cellular organisms
- Asexual reproduction in multicellular organisms and binary fission in unicellular organisms
Binary Fission:
The process that bacteria use to carry out cell division
Diploid:
Two copies of a chromosomes (one from the biological mother and one from the biological father)
Phases of the Cell Cycle: G1
Sub-cellular structures duplicate, structures include mitochondria and ribosomes but excluding chromosomes
Phases of the Cell Cycle: S
DNA replicates to form 2 copies of each chromosome
Phases of the Cell Cycle: G2
- DNA is checked for errors made during replication
- Done using enzymes, and any errors can be fixed
Phases of the Cell Cycle: Mitosis
One set of chromosomes is pulled to each end of the cell and the nucleus divides to form two nuclei
Phases of the Cell Cycle: Cytokinesis
- From 1 parent cell to two daughter cells
- Cytoplasm and cell membrane divide to create two separate diploid cells each with identical chromosomes
Phases of the Cell Cycle: G0
- Temporary cell resting
- Some cells will never divide again e.g. nerve cells
What does mitosis make?
Cell division that makes 2 diploid daughter cells that are genetically identical to the parent cell and to each other
What are all the phases of the cell cycle?
- G1
- S
- G2
- Mitosis
- Cytokinesis
- G0
What are all the phases of mitosis?
- Prophase
- Metaphase
- Anaphase
- Telophase
What happens in the prophase of mitosis?
- The nuclear membrane disappears
- The DNA unwinds and condenses into chromosomes consisting of two sister chromatids
- Spindle fibres form and become visible
What happens in the metaphase of mitosis?
- Chromosomes (made up of 2 sister chromatids) line up along the equator of the cell
- Spindle fibres attach to the chromosome at the centromere
What happens in the anaphase of mitosis?
- Sister chromatids are pulled apart (separated) towards the poles of the cell by the spindle fibres
What happens in the telophase of mitosis?
- Nuclear membrane forms around each of the sets of chromosomes separating them from one another
- DNA de-condenses
- 2 nuclei are formed
1 chromosome =
2 sister chromatids
Diagram of the cell cycle:
Diagram of the parent cell:
Diagram showing the phases of mitosis:
Diagram of cytokinesis:
The cell cycle:
series of stages that a cell goes through when it grows and divides
How does DNA replicate in the S phase of the cell cycle?
- still say that there are 46 chromosomes in the nucleus after DNA has replicated as the number of chromosomes is counted by the number of centromeres present
- when the 46 chromosomes duplicate there would still be 46 chromosomes except each chromosome would be made up of 2 sister chromatids (attached to the centromere) instead of 1
- 46 chromatids to 92 chromatids (but still 46 chromosomes) before and after replication
