12 Questions
What is the average cell cycle span for a mammalian cell?
24 hours
Which phase of the cell cycle involves the synthesis of DNA?
S phase
What is the main difference between cytokinesis and karyokinesis?
Cytokinesis is the division of cytoplasm, while karyokinesis is the division of the nucleus.
Which stage of interphase prepares the cell for division and generates RNA and proteins required for mitosis?
G2 phase
What is the purpose of the G0 phase in the cell cycle?
To remain inactive unless needed
During which phase of the cell cycle do cells grow and prepare the DNA to replicate?
G1 phase
What is the main reason mitosis is referred to as equational division?
Parent and progeny cells have the same number of chromosomes
In which stage of the cell cycle do chromosomes move to the spindle equator?
Metaphase
What is synapsis in the context of cell division?
The pairing of homologous chromosomes
How does cytokinesis in plant cells differ from that in animal cells?
Animal cytokinesis forms a cell plate
When does crossing over between homologous chromosomes occur?
Zygotene stage of prophase I in meiosis
In which type of gamete formation do the daughter cells differ in size?
Formation of female gametes
Study Notes
Cell Cycle Overview
- Average cell cycle span for a mammalian cell is 24 hours.
Cytokinesis vs. Karyokinesis
- Cytokinesis: cell division of cytoplasm that occurs during the M phase of the cell cycle.
- Karyokinesis: separation of daughter chromosomes corresponding to the M phase of the cell cycle.
Interphase
- G1 phase (Gap 1): cell is metabolically active, grows, and prepares DNA to replicate.
- S phase (Synthesis): DNA synthesis occurs, DNA quantity doubles, but the number of chromosomes remains unchanged.
- G2 phase (Gap 2): cell grows and prepares for division, RNA and proteins required for mitosis are generated.
G0 (Quiescent Phase)
- Cells exit the G1 phase to enter an inactive stage, called G0 phase, in adult animals.
- Cells in G0 phase do not proliferate unless needed to replace lost cells due to injury or cell death.
- Cells in this phase tend to become inactive, stop dividing, and become specialized through differentiation.
Mitosis
- Mitosis is called equational division because the number of chromosomes in parent and progeny cells is the same.
Cell Cycle Stages
- Metaphase: chromosomes are moved to the spindle equator.
- Anaphase: centromere splits, and chromatids separate.
- Zygotene stage of prophase 1 in meiosis: pairing between homologous chromosomes takes place.
- Pachytene stage of prophase 1 in meiosis: crossing over between homologous chromosomes takes place.
Meiosis
- Synapsis: homologous chromosomes pair together during Zygotene of prophase-I of meiosis.
- Bivalent or tetrad: pair of complexes formed by a pair of synapsed homologous chromosomes during the zygotene of prophase I of meiosis.
- Chiasmata: X-shaped structure formed by paired chromosomes during diplotene, where crossing over between two non-sister chromatids takes place.
Cytokinesis in Plant and Animal Cells
- Plant cytokinesis: occurs by cell plate formation, cell plate moves to the centre and extends towards the exterior.
- Animal cytokinesis: occurs by cleavage, cleavage begins at the periphery and advances inwards.
Meiosis in Human Beings
- Formation of male gametes (sperms): four daughter cells formed during meiosis are equal in size.
- Formation of female gamete (ovum): four daughter cells formed during meiosis are unequal in size, with one big mature ovum and 3 small polar bodies.
Test your knowledge on cell cycle, cell division, and interphase with this quiz. Learn about the average cell cycle span for a mammalian cell, differentiate between cytokinesis and karyokinesis, and understand the events that occur during interphase.
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