Mitosis and the Mitotic Cell Cycle Flashcards
In eukaryotes DNA is organised into …
…chromosomes
Chromosomes can be stained and examined using a…
…light microscope.
The chromosomes can be organised by size and shape into…
…a karyotype
Length of DNA in a human cell ?
2m
In humans there are usually two of each …
…chromosome (diploid 2C) in our somatic cells
In some stages of the life cycle of some organisms there is one copy of …
…each chromosome (haploid 1C).
Species with more than 2 copies of each chromosome are described as…
…polyploid
Most higher plants are …
…polyploid
Species with four copies of each chromosome are…
…tetraploid 4 C
In some species there are three copies …
…(triploid 3C)
The replication of DNA and its subsequent distribution into
two daughter cells is one of the most …
…fundamental processes
carried out in living organisms
Mitosis was first described by …
…Strasburger in 1880
Strasburger in 1880 divided mitosis into four phases:
1) prophase (in which the chromosomes become visible).
2) metaphase (where the chromosomes align at the
equator of the cell).
3) anaphase(where the two chromosome sets move to
opposite poles of the dividing cell).
4) telophase (where the new nuclear membranes are
formed and the chromosomes disappear).
Observations made by Eduard Strasburger in 1880 from a living plant cell in a…
…hair cell from a Tradescantia flower.
What occurs in the interphase?
The cell is carrying out its normal activities. It is not clear if the cell is in G1, S-phase or G2.
Cells in S-phase are …
…replicating their DNA
What occurs in Early Prophase?
The cell passes out of G2 Interphase and enters Mitosis (M-Phase).
Here, the nuclear membrane starts to degrade.
The nucleolus vanishes.
The Chromosomes condense to become Visible.
the chromosomes consist of…
…two chromatids
What occurs in Late Prophase?
The chromosomes continue to shorten and thicken. The spindle forms from the poles of the cell.
What occurs at Metaphase?
The spindle fibres attach to the chromosomes at
the Centromere (the Kinetochore within the
centromere). The chromosomes line up
along the equator of the cell.
Material which is dividing can be treated with …
…a mitotic poison such as colchicine (from the autumn crocus). This disrupts the metaphase.
At metaphase, how many chromatids are in each chromosome?
2
Treatment of dividing material during the metaphase with a mitotic poison, stops and disrupts the…
…spindle forming and the chromosomes are ‘liberated’.
- Counting cells where this takes place can give an indication of the kinetics of the cell cycle and enable the cell doubling time to be determined.
What occurs in the Anaphase?
- The chromatids
separate at their
centromeres - One chromatid from
each of the chromosome moves to opposite poles of the cell.
What occurs in the Telophase?
- The chromosomes de-condense (a reverse of prophase) forming two nuclei at the poles of the cell.
- Each chromosome now consists of one DNA molecule (one chromatid).
- The process is completed when cytokinesis forms two daughter cells. Each daughter cell passes into G1 of Interphase
What happens in Cytokinesis?
The two cells divide
The process of cytokinesis differs between…
…plants and animal cells
Why does cytokinesis differ in animal and plant cells?
Because animal cells do not have a cell wall
What are the functions of Mitosis?
1) Reproduction
2) Growth and development
Describe reproduction of an amoeba.
1) An amoeba
2) A single-celled eukaryote, is dividing into two cells.
3) Each new cell will be an individual organism