Topic 5 The Mitotic Cell Cycle. Flashcards
What is growth of a multicellular organism a result of?
Growth of a multicellular organism is a result of parent cells dividing to produce genetically identical daughter cell.
What divides first during cell division and why?
What kind of cells is the nucleus found in?
What is DNA?
During cell division the nucleus divides first, followed by division of the whole cell.
Division of the nucleus to produce two genetically identical nuclei is achieved through the process of mitosis with each of the two daughter cells containing its own nucleus, which is important because the nucleus controls the cell’s activities because it contains the genetic material DNA.
The nucleus is found in eukaryotic cells.
DNA/deoxyribonucleic acid acts as a set of instructions, or code, for life.
What is a chromosome?
Chromosomes are large structures of DNA and proteins. DNA in cells is wrapped around positively charges globular proteins called histones. This results in a structure called chromatin which is a combination of DNA and the protein histones. Chromatin is then coiled into structures known as chromosomes.
State the components that make up a chromosome.
- DNA.
- Histone protein.
- Sister chromatids.
- Centromere.
- Telomere.
What is mitosis?
Mitosis is nuclear division that produces two genetically identical daughter nuclei, each containing the same number and type of chromosomes as the parent nucleus.
What is the purpose of mitosis?
- Growth of multicellular organisms.
- Replacement of damaged or dead cells and repair of tissues by cell replacement.
- Asexual reproduction: the production of genetically identical offspring from one single parent through the process of mitosis.
- Immune reponse: the cloning of lymphocytes during immune reponse.
What are the three phases of the cell cycle?
Interphase.
- G1 is the first growth phase where the cell recieves a signal committing the cell to DNA replication and the cell grows physically to increase the volume of proteins and organelles and prepares to enter the S phase.
- S phases or synthesis of DNA phase is when the DNA replication takes place.
- G2 is a second growth phase where the cell prepares for mitosis.
Nuclear division/ in this case Mitosis.
- M phase or mitosis phase is when nuclear division takes place.
Cytokinesis.
- Cell division.
G stands for gap/growth.
S stands for synthesis of DNA.
M stands for mitosis.
Cytokinesis means cell division.
What is the mitotic cell cycle and what are the four main stages of the cycle?
The mitotic cell cycle is a process of cell division that results in the formation of two identical daughter cells.
The mitotic cell cycle consists of four stages:
- Prophase.
- Metaphase.
- Anaphase.
- Telophase.
An acronym for the four stages of the mitotic cell cycle is PMAT.
What happens during prophase?
- During prophase, the chromatin condenses to become short, thick and visible in the nucleus to form chromosomes.
- The nucleolus disappears and the nuclear membrane starts to break down.
- The centrosomes, each with a pair of centrioles move apart to the opposite poles of the cell. Proteins begin to form spindle fibres which attach to the centromere of each chromosome. These spindle fibres move the chromosomes towards the centre of the cell.
What happens during metaphase?
- During metaphase, microtubules of the spindle interact with chromosomes. This causes the chromosomes to move and align along the middle of the cell or the equatorial plate.
- Sister chromatids are held at the centromere forming the presence of protein structures called kinetochore at the surface.
- The kinetochore holds the chromosomes and attaches them to the spindle.
What happens during anaphase?
- During anaphase, the sister chromatids separate at the kinetochores and the daughter chromosomes along with the divided centromere move towards the opposite poles as the microtubule shortens.
- The poles of the spindle also move apart and help to separate the chromosomes.
What happens during telophase?
- During telophase, the chromatids have reached the poles of the cell where they decoil.
- The spindle apparatus breaks down and nuclei and nucleoli reform which triggers the reformation of the nuclear membrane.
Centrioles do not play a role in forming the spindle apparatus in plant cells and that is because plant cells fo not contain centrioles.
What happens during cytokinesis?
During cytokinesis, the central cell membrane is pulled inwards by the cytoskeleton. This creates a cleavage furrow which gradually deepens and eventually divides the cytoplasm to form two daughter cells.
What are telomeres?
Repetitive sequence of DNA at the end of a chromosome that protects genes from the chromosome shortening that happens at each cell division.
What are roles of telomeres?
The enzyme that performs the role of adding bases to telomeres is called telomerase. The main function of telomeres is therefore to prevent the progressive loss of genes and DNA during cell division and to allow continued replication of a cell.
