lecture 6 - cell membrane Flashcards
(32 cards)
What are the phases of the cell cycle?
The cell cycle includes:
1. Interphase: Divided into G1 (growth phase), S (DNA synthesis), and G2 (second growth phase).
2. Mitosis (M phase): Nuclear division.
3. Cytokinesis: Cytoplasm division.
What happens during interphase?
• G1: The cell grows, and cytoplasmic organelles increase.
• S: DNA is synthesized (semi-conservative replication), and new histones are produced.
• G2: DNA is checked for errors, and the cell prepares for mitosis.
What are the stages of mitosis?
- Prophase: Chromosomes condense, nuclear envelope breaks down, spindle fibers form.
- Metaphase: Chromosomes align at the cell’s equator; spindle fibers attach.
- Anaphase: Centromeres divide, and chromatids are pulled to opposite poles.
- Telophase: Nuclear envelopes reform around each set of chromosomes; chromosomes uncoil.
What is cytokinesis?
It is the division of the cytoplasm, completing the formation of two daughter cells.
How is mitotic index calculated?
The mitotic index is the number of cells undergoing mitosis divided by the total number of cells in the field of view.
Why is mitosis important?
• Growth.
• Repair of damaged tissues.
• Asexual reproduction in some organisms.
What are checkpoints in the cell cycle?
• G1 checkpoint: Ensures the cell is ready for DNA synthesis.
• G2 checkpoint: Ensures DNA replication is complete and error-free.
• Metaphase checkpoint: Ensures chromosomes are correctly attached to spindle fibers.
What happens if a cell fails a checkpoint?
The cell exits the cycle and enters the G0 phase, where it no longer divides.
What role do stem cells play?
Stem cells are unspecialized cells that can differentiate into any type of cell. They are found in:
• Bone marrow.
• Umbilical cord blood.
• Embryos (with ethical considerations).
How is mitosis observed in plants?
Mitosis occurs in meristems, located at the growing tips of shoots and roots.
What is cancer, and how does it relate to mitosis?
Cancer results from uncontrolled mitosis due to mutations, leading to tumor formation.
What are the types of genes controlling cell division?
Tumor Suppressor Genes (TSG): Inhibit cell division. Mutations can inactivate them, leading to uncontrolled growth.
Proto-oncogenes: Stimulate normal cell division. Mutations can turn them into oncogenes, causing excessive division.
What is the role of methylation in cancer?
Abnormal DNA methylation can affect the transcription and translation of cancer-related genes, promoting tumor growth.
What is the importance of complementary base pairing in DNA replication?
It ensures that adenine pairs with thymine, and cytosine pairs with guanine, maintaining genetic accuracy.
What is the Length of the Cell Cycle?
In eukaryotic cells, the cell cycle takes less than 24 hours, varying by cell type, temperature, oxygen, and nutrients.
What are the Types of Mutations That Cause Cancer?
•Tumor suppressor gene mutations lead to uncontrolled cell division due to the absence of inhibitory proteins.
•Mutations in proto-oncogenes make them oncogenes, leading to excessive stimulation of cell division.
What is mitosis?
Mitosis is a type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cell.
What are daughter cells?
Daughter cells are the cells produced by cell division.
What is a chromatid?
A chromatid is one of the two strands of a chromosome joined together by a single centromere prior to cell division.
What is a centromere?
A centromere is the region where the two copies of DNA after replication are joined together.
What is interphase?
Interphase is the period of the cell cycle when the cell is not dividing.
What happens during anaphase?
centromeres divide into two and spindle fibres pull individual chromatids to opposite poles of the cell.
What happens during metaphase?
Chromosomes arrange themselves across the equator of the cell.
What happens during anaphase?
• Centromeres divide into two.
• Spindle fibers pull individual chromatids to opposite poles of the cell.
