Cell Cycle and DNA Replication Flashcards
What is the cell cycle?
- Duplication of its DNA
- Division of cytoplasm and organelles
- Production of two daughter cells
What are the stages of the cell cycle and their events?
- Interphase: Cell growth and DNA replication
- Mitosis: Division of the nucleus (Prophase, Metaphase, Anaphase, Telophase)
- Cytokinesis: Division of the cytoplasm
What is the G1 Phase?
Cell growth, synthesis of proteins and increase in mass/volume
What is the S Phase?
DNA synthesis- replication of chromosomes
What is the G2 Phase?
Replication of organelles
Eg. Mitochondria
What are cell cycle checkpoints?
- Temporarily stop the cycle to check for damage
- If no damage is detected the cell continues through the cycle
What is the G1 Checkpoint?
- Checks for DNA damage and stops proliferation of damaged cells
- Restriction point- cell commits to entering the cycle
What is the G2 Checkpoint?
- Checks for DNA damage
- Some DNA repair
- Stops proliferation of damaged cells
What is the M Checkpoint?
Ensures centromeres are attached to spindle fibers before chromatid separation
What happens to specialized cells in the cell cycle?
- Only stem cells continuously go through the cycle
- Cells that leave the cycle enter G0 and differentiate
- Specialized cells never divide again and cannot re-enter the cycle
What is apoptosis?
- Programmed cell death that does not release lysosomal enzymes that could damage surrounding cells/tissues
- Around 10,000 body cells are destroyed daily
What role does apoptosis play during embryonic development?
Removes unwanted structures
What are the steps of apoptosis?
- Chromatin condenses
- Membrane blebbing occurs
- Apoptotic bodies form and are engulfed by phagocytes
What is the structure of DNA?
- Made of nucleotides joined by phosphodiester bonds formed in condensation reactions
- Double-stranded structure
How are the strands of DNA held together?
- 3 hydrogen bonds between cytosine and guanine
- 2 hydrogen bonds between adenine and thymine
What are the steps of DNA replication?
- DNA Helicase breaks hydrogen bonds
- Strands Free DNA nucleotides form hydrogen bonds with complementary bases
- DNA Polymerase forms phosphodiester bonds between nucleotides using condensation reactions
- Each strand serves as a template for the synthesis of a new complementary strand.
What does semi-conservative replication mean?
- Each new DNA molecule contains one original (parent) DNA strand
- Also contains one newly synthesized DNA strand
