1.6 Syllabus
-Mitosis: It is the division of the cell's nucleus into 2 identical daughter nuclei containing the same number of chromosome as the mother cell.
Why do cells divide?
-Cell division allow growth of organism by producing more copies of cell and allow for more cell differentiation to occur
-Cell cycle: series of events through which cells pass to divide and create 2 identical daughter cells
-Chromosome: Every eukaryote has genes on chromosome and each chromosome has pair which are one from each parent.
-Human 23 pairs, diploid num: 46
Gametes: Haploid that pair up with other half in fertilization
-Terminology
Centromere: Part of chromosome that links sister chromatids
Sister chromatids: Duplicated chromosomes attached by centromere
Chromosomes: When chromatids separate
Chromatin: Chromosome uncoiled:
Spindle microtubules: Spindle fibres
Centrioles: Organize spindle fibres (2 centrioles held by protein mass: Centrosome)
Why do cells divide?
- Large cells have reduced SA:VOL so it’s less sufficient than smaller cells
- Organism grows, need to produce more cells
-Cell division allow growth of organism by producing more copies of cell and allow for more cell differentiation to occur
-Cell cycle: series of events through which cells pass to divide and create 2 identical daughter cells
-Chromosome: Every eukaryote has genes on chromosome and each chromosome has pair which are one from each parent.
-Human 23 pairs, diploid num: 46
Gametes: Haploid that pair up with other half in fertilization
-Terminology
Centromere: Part of chromosome that links sister chromatids
Sister chromatids: Duplicated chromosomes attached by centromere
Chromosomes: When chromatids separate
Chromatin: Chromosome uncoiled:
Spindle microtubules: Spindle fibres
Centrioles: Organize spindle fibres (2 centrioles held by protein mass: Centrosome)
U4. Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
Interphase: - Many metabolic reaction occurs
-DNA replication in nucleus and protein synthesis in cytoplasm
=These are the part of cell cycle that x involve cell division
-Number of mitochondria increase due to growth and division
Three phase
2. S phase: DNA replication
3. G2 phase: Cell finishes growing and prepare for cell division
-DNA replication in nucleus and protein synthesis in cytoplasm
=These are the part of cell cycle that x involve cell division
-Number of mitochondria increase due to growth and division
Three phase
- G1 phase: -Increase volume of cytoplasm/-Organelles produced/-Protein synthesized
2. S phase: DNA replication
3. G2 phase: Cell finishes growing and prepare for cell division
U1. Mitosis is division of the nucleus into 2 genetically identical daughter nuclei
U2. Chromosomes condense by supercoiling during mitosis.
-Can only occur when DNA in nucleus are replicated
-Each single DNA molecules converted into 2 identical DNA molecules= Chromatids that passes to each daughter nucleus during mitosis
-Mitosis involved whenever cells with genetically identical nuclei r required in eukaryotes.
Ex) growth/ embryonic development/ tissue repair
1. Early prophase:
-DNA supercoils and chromatin condenses and become sister chromatids that’s visible under microscope
-Spindle microtubules grow from MTOC .
2. Late prophase
-Spindle microtubules extend from each pole to the equator.
-Each chromosome consists 2 identical chromatids formed by DNA replication in interphase and held tgth by centromere.
-Nucleolus and nuclear membrane break down
3. Metaphase
-Spindle fibres from each of centrosomes and continue to and attach to the centromere on each chromosome.
-2 attachment parts on opposite sides of each centromere allow chromatids of chromosome to attach to microtubules from different poles
-Contraction of spindle fibres cause the sister chromatids to line up along the equator
4. Anaphase
Start of anaphase, each centromere divides allowing pairs of sister chromatids to separate
-Continue contraction of microtubule spindle fibres that cause separation of sister chromatids
-Chromatids now referred to as chromosomes
-Spindle microtubules pull them rapidly towards the pole of the cell
=Mitosis produce 2 identical nuclei because sister chromatids pulled to opposite poles
5. Telophase
Chromosomes arrives at poles
-Microtubule spindle fibers disappear
-At each pole the chromosomes r pulled into tight group near MTOC and nuclear membrane reforms
-Chromosomes uncoil, decondense to chromatin which is not visible under light microscope
RELATED QUESTION:
Q. Process of Mitosis
Answer: G-1 growth phase is a synthesis of proteins. S-phase (synthesis phase) is replication of DNA. G-2 (2nd growth phase): continued growth of cytoplasm. At prophase, chromosomes supercoil to prepare for mitosis. In metaphase, chromosome lines up at equatorial plate and spindle fibres attach to centromeres. In anaphase, chromatids move along spindle microtubules and spindle fibres move chromatids toward opposite poles. Telophase: Nuclear membrane form around each chromosome. Cytokinesis occurs, which is the process that new plasma membrane forms between the nuclei. A new cell wall forms. Mitosis results in 2 cells with identical nuclei. Interphase is the longest phase
-Each single DNA molecules converted into 2 identical DNA molecules= Chromatids that passes to each daughter nucleus during mitosis
-Mitosis involved whenever cells with genetically identical nuclei r required in eukaryotes.
Ex) growth/ embryonic development/ tissue repair
1. Early prophase:
-DNA supercoils and chromatin condenses and become sister chromatids that’s visible under microscope
-Spindle microtubules grow from MTOC .
2. Late prophase
-Spindle microtubules extend from each pole to the equator.
-Each chromosome consists 2 identical chromatids formed by DNA replication in interphase and held tgth by centromere.
-Nucleolus and nuclear membrane break down
3. Metaphase
-Spindle fibres from each of centrosomes and continue to and attach to the centromere on each chromosome.
-2 attachment parts on opposite sides of each centromere allow chromatids of chromosome to attach to microtubules from different poles
-Contraction of spindle fibres cause the sister chromatids to line up along the equator
4. Anaphase
Start of anaphase, each centromere divides allowing pairs of sister chromatids to separate
-Continue contraction of microtubule spindle fibres that cause separation of sister chromatids
-Chromatids now referred to as chromosomes
-Spindle microtubules pull them rapidly towards the pole of the cell
=Mitosis produce 2 identical nuclei because sister chromatids pulled to opposite poles
5. Telophase
Chromosomes arrives at poles
-Microtubule spindle fibers disappear
-At each pole the chromosomes r pulled into tight group near MTOC and nuclear membrane reforms
-Chromosomes uncoil, decondense to chromatin which is not visible under light microscope
RELATED QUESTION:
Q. Process of Mitosis
Answer: G-1 growth phase is a synthesis of proteins. S-phase (synthesis phase) is replication of DNA. G-2 (2nd growth phase): continued growth of cytoplasm. At prophase, chromosomes supercoil to prepare for mitosis. In metaphase, chromosome lines up at equatorial plate and spindle fibres attach to centromeres. In anaphase, chromatids move along spindle microtubules and spindle fibres move chromatids toward opposite poles. Telophase: Nuclear membrane form around each chromosome. Cytokinesis occurs, which is the process that new plasma membrane forms between the nuclei. A new cell wall forms. Mitosis results in 2 cells with identical nuclei. Interphase is the longest phase
U3. Cytokinesis occurs after mitosis and is different in plant and animal cells
-Mitosis: Division of nucleus
-Cytokinesis: Division of cytoplasm-> cells can divide after mitosis when 2 genetically identical nuclei r present in cell.
1. Animal cells
-Inward pull of plasma membrane that produces the characteristic of cleavage furrow
→ Accomplished using ring of contractile protein=microfilaments immediately inside plasma membrane at equator
→ Proteins are actin and myosin and are similar to protein that cause contraction in muscle
- When cleavage furrow reaches centre of cells, its pinched apart to form 2 daughter nuclei
2. Plant cells
-During telophase, membrane enclose vesicles derived from Golgi apparatus migrate to center of the cell (equator)
-Then, vesicle fuse to form tubular structure
-Tubular structure merge to form 2 layers of plasma membrane such as cell plate
-Cell plate continues to develop until it connects with the existing cell’s plasma membrane.
-This completes the division of cytoplasm and formation of daughter cell
-Next stage, pectins and other substances to be brought in vesicles and deposit through exocytosis between 2 new membranes
→ This forms middle lamella that will link the new cell walls
-Both daughter cells then bring cellulose to the equator and deposit it by exocytosis adjacent to middle lamella. Each cell builds its own cell wall adjacent to cell wall.
-Cytokinesis: Division of cytoplasm-> cells can divide after mitosis when 2 genetically identical nuclei r present in cell.
1. Animal cells
-Inward pull of plasma membrane that produces the characteristic of cleavage furrow
→ Accomplished using ring of contractile protein=microfilaments immediately inside plasma membrane at equator
→ Proteins are actin and myosin and are similar to protein that cause contraction in muscle
- When cleavage furrow reaches centre of cells, its pinched apart to form 2 daughter nuclei
2. Plant cells
-During telophase, membrane enclose vesicles derived from Golgi apparatus migrate to center of the cell (equator)
-Then, vesicle fuse to form tubular structure
-Tubular structure merge to form 2 layers of plasma membrane such as cell plate
-Cell plate continues to develop until it connects with the existing cell’s plasma membrane.
-This completes the division of cytoplasm and formation of daughter cell
-Next stage, pectins and other substances to be brought in vesicles and deposit through exocytosis between 2 new membranes
→ This forms middle lamella that will link the new cell walls
-Both daughter cells then bring cellulose to the equator and deposit it by exocytosis adjacent to middle lamella. Each cell builds its own cell wall adjacent to cell wall.
U5. Cyclins are involved in the control of the cell cycle.
-CDK enzyme exists in cytoplasm at constant concentration, but in inactive form
-To active CDK, it must bind with cyclin, a protein the fluctuates in a concentration
→Cyclin: Used to ensure tasks are performed at the correct time and that the cell only moves on to the next stage of the cycle when it is appropriate.
-When combined, the kinases then become active and attach phosphate groups to other proteins in the cell
-The attachment of phosphate triggers the other proteins to become active and carry out tasks specific to one of the phases of cycle
-Unless the cyclins reach a threshold concentration, the cell does not progress to the next stage of the cell cycle
Cyclins therefore control the cell cycle and ensure that cells divide when new cells are needed, but not at other times.
-To active CDK, it must bind with cyclin, a protein the fluctuates in a concentration
→Cyclin: Used to ensure tasks are performed at the correct time and that the cell only moves on to the next stage of the cycle when it is appropriate.
-When combined, the kinases then become active and attach phosphate groups to other proteins in the cell
-The attachment of phosphate triggers the other proteins to become active and carry out tasks specific to one of the phases of cycle
-Unless the cyclins reach a threshold concentration, the cell does not progress to the next stage of the cell cycle
Cyclins therefore control the cell cycle and ensure that cells divide when new cells are needed, but not at other times.
U6. Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumors.
-Tumors can form cells that have lost control of their cell cycles
-Mutations occur spontaneously through DNA replication/recombination
-Substances that can cause unnaturally high rate of mutations are called mutagens e.g. X-ray, UV ray
-Substances that can cause unnaturally high rate of mutations resulting in cancer are called carcinogens ex) cigarettes
→Benign Tumors: Unlikely to cause harm
→Malignant Tumors: Likely to be life-threatening
-Metastasis
= Movement of cells from a primary tumor to set up secondary tumors in other parts of body
-Mutations occur spontaneously through DNA replication/recombination
-Substances that can cause unnaturally high rate of mutations are called mutagens e.g. X-ray, UV ray
-Substances that can cause unnaturally high rate of mutations resulting in cancer are called carcinogens ex) cigarettes
→Benign Tumors: Unlikely to cause harm
→Malignant Tumors: Likely to be life-threatening
-Metastasis
= Movement of cells from a primary tumor to set up secondary tumors in other parts of body