Cell and Nuclear Division Flashcards
List The Functions of Cell Division.
- Growth
- Repair of Tissues and Organs
- Maintenance to Replace Dead or Dying TIssues
The cycle cycle takes 12-24 hours for animal cells.
Define Mitosis.
Parent cells divide into two genetically identical daughter cells.
Results of Mitosis.
- Two daughter cells are identical to the mother cell.
- Mitosis ensures that all body cells have a complete number and form of chromosomes (all human cells resulting from mitosis will be diploid, 2n = 43).
Note: Mitosis occurs in somatic cells (a plant or animal cell that forms the body of the organism; excludes reproductive cells).
Interphase:
G1 Phase (1)
- Growth
- Increase the amount of cytoplasm and organelles.
Interphase:
S Phase (2)
- DNA Replication
- Ensures that new cells have equal amounts of DNA.
Interphase:
G2 Phase (3)
- Growth
- Organelles for division and mitochondria are formed.
- Centrioles are duplicated.
Interphase
- DNA exists as a chromatin.
- Nucleolus is surrounded by a nuclear envelope.
- In G2, centrioles are duplicated.
Prophase
- Chromatin supercoils into chromosomes.
- Nuclear membrane breaks down.
- Centrioles move to opposite poles of the cell and sprout microtubules.
Note: Two chromosome arms are called sister chromatids and the chromosomes are joined at the centromeres.
Metaphase
- Microtubules (spindle fibres) attach to the centromere (kinetochore proteins) and guide the chromosomes to the metaphase plate.
Note: The metaphase plate is the center of the cell.
Anaphase
- Sister chromatids are separated and moved to opposite poles by microtubules.
- Separated sister chromatids are now refered to as chromosomes.
- Each pole has a complete set of chromosomes.
Telophase
- Chromosomes reach opposite ends of the cell.
- Chromosomes start to unwind and become chromatin.
- Microtubules break down.
- Nuclear membrane reforms.
Cytokinesis
- The cytoplasm of a cell is divided between the two daughter cells.
- Can begin as soon as chromosomes are separated and are far enough apart to ensure none end up in the wrong cell.
- All cytoplasm and the contents of the mother cell are shared between the two daughter cells.
Note: Cytokinesis is different in plant and animal cells.
Sometimes there in unequal sharing of the cytoplasm.
Outline One Scenario.
Oogenesis (egg) produces 4 haploid cells (n):
* 3 out of 4 of the cells donate their cytoplasm organelles to the 4th because they are much too small to produce a zygote
* This unequal cytokinesis provides the zygote with the resources that are needed to survive until it is implanted in the walls of the uterus.
Cytokinesis in Animal Cells.
- Contractile proteins, actin and myosin pinch the cell along its equator.
- Meaning, it forms a cleavage furrow.
Note: A cleavage furrow “draws the plasma membrane toward the cell center, pinching the cytoplasm into two lobes that are subsequently separated into two cells.”
Cytokinesis in Plant Cells.
- Vesicles move to the equator where they fuse to form tubular structures.
- More vesicles fuse and these tubular structures merge to form two layers of membrane across the whole equator which develops into the membranes of the new daughter cells.
- Pectin is brought in vesicles and deposited by exocytosis between the two membranes.
- Cellulose is deposited by exocytosis to form the cell wall.
Note:
* Pectin is “any of a group of water-soluble carbohydrate substances that are found in the cell walls and intercellular tissues of certain plants.”
* Cellulose is “a molecule, consisting of hundreds – and sometimes even thousands – of carbon, hydrogen and oxygen atoms. It is the main substance in the walls of plant cells.”
Define Tumors.
An Abnormal Group of Cells.
Define Benign Tumors.
Cells ‘stick’ to each other and do not invade nearby tissues or move to other parts.
Define Maligant Tumors.
Cells become detached and move elsewhere in the body and develop into secondary tumors.
Define Carcinogens.
Cancer causing chemicals, such as viruses, mutagens, and x-rays.
Define Mutagens.
Agents that cause gene mutations.
Note: Mutagens can cause cancer.
Define Mutations.
Random changes to the DNA sequence (essentially, ‘spelling mistakes’ in the DNA).
Define Oncogenes.
- Most genes do not cause cancer when they mutate.
- The few that can become cancer-causing after mutating are known as oncogenes.
- Oncogenes are involved in the control of the cell cycle and cell division.
Define Primary Tumors.
- Several mutations must occur in the same cell for it to become a tumor.
- When a tumor cell has been formed, it divides repeatedly.
- This group of cells is called a primary tumor.
Define Metastasis.
The movement of cells from a primary tumor to set up secondary tumors in other parts of the body.
