MITOTIC CYCLE Flashcards
What happens during anaphase in mitosis?
- Sister chromatids separate at the centromere.
- Spindle fibers shorten, pulling chromatids (now chromosomes) to opposite poles.
What occurs during telophase in mitosis?
- Chromatids reach opposite poles and decondense.
- Nuclear envelopes reforms
- Nucleoulus reforms
- Centrosomes replicate
- Spindle fibers break down.
What are telomeres?
Protective structures at the ends of chromatids made of non-coding, repetitive DNA sequences.
What are stem cells?
Stem cells are undifferentiated cells capable of dividing via mitosis and differentiating into specialized cell types.
Outline the “levels” of stem cell potency.
Totipotent: Can form any cell type, including placental cells.
Pluripotent: Can form any cell type in the developing embryo (not placental cells).
Multipotent: Can form a limited range of cell types (e.g., blood cells).
What roles do stem cells play in the body?
- Cell replacement
- Tissue repair
- Growth
How do benign and malignant tumors differ?
Benign tumors: Do not spread; remain localized.
Malignant tumors: Spread through blood/lymph (metastasis), invading other tissues and forming secondary growths.
Describe the structure of a chromosome.
Chromatid: One of two identical halves of a replicated chromosome.
Centromere: Region where sister chromatids attach to each kinetochore.
Telomeres: Protective sequences at chromosome ends.
Chromatin: Tightly coiled DNA around histone proteins.
What are the phases of the cell cycle, and what happens in each?
G1 phase:
Cell growth
Synthesis of proteins and other substances
S phase:
DNA replication; sister chromatids form.
G2 phase:
The cell grows, and the newly synthesized DNA is checked and repaired.
Preparation for mitosis: Tubulin production for spindle fibers.
M phase: Mitosis, nuclear division
Cytokinesis: Cell division forming two identical daughter cells.
How does cytokinesis differ in plant and animal cells?
Animal cells: Cytoplasm constricts to divide the cell.
Plant cells: Vesicles form a cell plate at the equator, which develops into a new cell wall.
What is mitosis, and why is it important?
Mitosis is the process of nuclear division producing two genetically identical daughter nuclei.
- It ensures genetic consistency for growth
- Ensures asexual reproductin
- Replacment and Repair of cells
- Regeneration of cells
- Successful immune response
What happens during prophase in mitosis?
- Nuclear envelope breaks down
- Nucleoulus disapears
- Chromosomes condesnse and have two sister chromatids
- Centrosomes move to opposite ends
Describe the events of metaphase in mitosis.
- Centrosomes reach opposite poles and organises production of microtubules
- Microtubules make up spindle fibers
- Chromosomes align at the equator
- Spinddle fibers attach to centromeres (Kinetochores) of sister chromatids.
- Each sister chromatid is attached to fibers from opposite poles.
What is the role of telomeres in DNA replication?
They ensure that no vital genes are lost during DNA replication by acting as a buffer zone. This helps because copying enzymes cannot replicate the very ends of DNA, so when teloemres are there they replicate till the end of the vital DNA genes, ensuring that vital genes are passed on.
What happens to cells without telomerase?
Their telomeres shorten with each division, leading to eventual cell death after a certain number of divisions.
How are telomeres related to aging?
The progressive shortening of telomeres in cells without telomerase is linked to the aging process.
Why can stem cells divide continuously?
They contain telomerase, which prevents the shortening of telomeres.
How are stem cells used in therapy?
Cell therapy works by the introduction of new adult stem cells to replace or repair damaged tissues. This is used in:
- Bone marrow transplants (for blood disorders)
- Skin regeneration (for burns)
- Tissue repair (like in heart disease or spinal cord injuries)
These stem cells develop into the needed specialized cells, aiding healing.
What causes a tumour to form?
Uncontrolled mitosis due to mutations in genes that regulate cell division.
What is an oncogene?
A mutated gene that can lead to cancer by causing uncontrolled cell division.
What is metastasis?
The process by which malignant tumour cells spread through the blood or lymphatic system to form secondary growths in other parts of the body.
Why are cancer cells able to divide indefinitely?
They contain telomerase and do not respond to normal signals that inhibit cell division, such as contact inhibition.
Desribe the stages of development in cancer
- Onocogenes arise due to carcinogens
- Cancer cells do not respond to signals from other cells and continues to divide by mitosis
- Cancer cells not removed by immune system and rapidly divide.
- Tumour gets bigger
- Tumour supplied with blood and lymph vessels. If malignant: Tumour spreads to other parts of the body via lymp and blood.
- Metastasis: Tumour invades other tissues. Secondary cancers form.
Gene
a part of the DNA that codes for a protein
Role of histone proteins
Histones serve to both package and organize DNA within the nucleus.
-Prevents entanglment of chromtaids
- Condenses the DNA tightly
How does mitosis aid tissue repair?
Replaces damaged or dead cells with identical ones.
What is the significance of mitosis in cell replacement?
Ensures continuous replacement of cells, like skin or gut lining.
How does mitosis enable asexual reproduction?
Creates genetically identical offspring from a single parent.
What role does mitosis play in regeneration?
Regenerates body parts in some animals, like axolotls and zebrafish.
How does mitosis support immunity?
Clones T and B lymphocytes for immune responses.
