LIFESCI 4 Lecture Notes - Lecture 4: Sister Chromatids, Actomyosin Ring, Dna Replication
Vid 4
Autosomal Cell Cycle
• Mostly in interphase
- G1 (gap 1): first growth stage of interphase
➢ Cell grows to full size & perform functions
- S (synthesis) phase: DNA replication
- G2 (gap 2): preparing for mitosis (check DNA; replicate centrosomes); cell finishes
growing
• Mitosis can start when cell has duplicated DNA in nucleus & 2 centrosomes in cytoplasm
Mitosis
• Prophase
- DNA condenses & organizes into chromosome structures
- Protein strands (microtubules) appear from centrosomes
- Nucleolus disappears
- Prometaphase
➢ Nuclear membrane breaks down
➢ Microtubules strands (spindle fibers) grow from centrosomes & attach to
kinetochore
• Metaphase
- Chromosomes align in the center of the cell
• Anaphase
- Microtubules shorten -> Chromosomes separate
- Poles of the cell move apart -> more separation of chromatids
• Telophase
- Spindle fibers broken up
- Nuclear membrane reappears around two sets of chromosomes
- Components of new cell begin to appear
- Chromosomes de-coil
Cytokinesis
• Cell compressed by contractile ring dividing cell in equal halves
• Components of the cells (rough ER, Golgi body, mitochondria) replicated by this time
• Enter G1 phase of interphase again
Germ line cell cycle
• Germ line cells -> meiosis -> gametes
- Germ line cells has 2 copies of chromosomes in 2n organisms -> haploid gametes
find more resources at oneclass.com
find more resources at oneclass.com
• DNA replicated in S phase
• sister chromatids attached together till
Meiosis II
• Meiosis I: 2 unique daughter cells with half
DNA of parent
• Meiosis II: 4 unique HAPLOID cells
- One copy of each chromosome
Meiosis
• Meiosis I = reductional division
• Meiosis II = equational division
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
G1 (gap 1): first growth stage of interphase. Cell grows to full size & perform functions. G2 (gap 2): preparing for mitosis (check dna; replicate centrosomes); cell finishes growing: mitosis can start when cell has duplicated dna in nucleus & 2 centrosomes in cytoplasm. Dna condenses & organizes into chromosome structures. Microtubules strands (spindle fibers) grow from centrosomes & attach to kinetochore: metaphase. Chromosomes align in the center of the cell: anaphase. Poles of the cell move apart -> more separation of chromatids: telophase. Nuclear membrane reappears around two sets of chromosomes. Components of new cell begin to appear. Cytokinesis: cell compressed by contractile ring dividing cell in equal halves, components of the cells (rough er, golgi body, mitochondria) replicated by this time, enter g1 phase of interphase again. Germ line cell cycle: germ line cells -> meiosis -> gametes. Germ line cells has 2 copies of chromosomes in 2n organisms -> haploid gametes.
