Cell Division Flashcards
What are the phases of the eukaryotic cell cycle?
Interphase (G1, S, G2) and Mitotic Phase (Mitosis & Cytokinesis)
What is the purpose of cell cycle checkpoints?
To ensure proper cell size, DNA replication, and spindle attachment before progressing to the next stage
How do somatic cells divide?
By mitosis, producing two genetically identical diploid (2n) daughter cells
How do gametes divide?
By meiosis, reducing chromosome number from diploid (2n) to haploid (n)
What happens during G1 phase?
Cell grows, performs normal activities, and replicates organelles; centrosomes begin replication
What occurs during S phase?
DNA is replicated, forming two identical DNA strands
What happens during G2 phase?
The cell checks DNA replication, produces mitotic enzymes, and completes centrosome replication
What are the stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase
What happens during Prophase?
Chromosomes condense, nuclear envelope disintegrates, spindle fibers attach to centromeres
What happens during Metaphase?
Chromosomes align at the metaphase plate
What happens during Anaphase?
Sister chromatids separate and move to opposite poles
What happens during Telophase?
Chromosomes decondense, nuclear envelope reforms, spindle breaks down
What is cytokinesis?
The cytoplasm divides, forming two identical daughter cells
What are the cell cycle checkpoints?
G1 (size, nutrition, DNA damage), G2 (size, replication), M (spindle attachment)
What proteins regulate the cell cycle?
Cyclin and CdK (Cyclin-dependent kinase); MPF (M-phase Promoting Factor) initiates mitosis
What is meiosis?
A type of cell division producing 4 genetically different haploid (n) gametes
What happens in Prophase I of meiosis?
Homologous chromosomes pair (synapsis), crossing over occurs, forming tetrads
What happens in Metaphase I?
Homologous pairs align randomly on the metaphase plate (independent assortment)
What happens in Anaphase I?
Homologous chromosomes separate, sister chromatids remain attached
What happens in Telophase I and Cytokinesis?
Two haploid (n) cells form, each chromosome still has two chromatids
What happens in Meiosis II?
Sister chromatids separate during Anaphase II, forming 4 haploid cells
What contributes to genetic variation in meiosis?
Crossing over (Prophase I), Independent assortment (Metaphase I), Random fertilization
How does mitosis differ from meiosis?
Mitosis: 1 division, 2 identical diploid cells; Meiosis: 2 divisions, 4 genetically unique haploid cells
