Cell Cycle, Mitosis, & Meiosis (Biology Summative) Flashcards
What is telomere?
The tip of a chromosome
Oogenesis
Production of female gametes (ova)
Starts during fetal development
Cell Division vs Nuclear Division
What is mitosis?
The division of the nucleus of the cell into two new nuclei
Explain
What happens in Synthesis (S) stage?
Replication of DNA
These are the cell’s control systems.
From these, the cell cycle stops until a go-ahead signal is received.
Checkpoints
* G1 Checkpoint (G1 to S)
* G2 Checkpoint (G2 to M)
* Spindle or M Checkpoint (Meta to Ana)
Explain
What happens in Gap 1 (G1)?
The cell just finished dividing, so in Gap 1, it is recovering from mitosis
Meiosis II
Telophase II and Cytokinesis II
- The cells split in half
- Four non-identical haploid daughter cells are produced from one original diploid cell
Meiosis II
Anaphase
- Centromeres split
- Sister chromatids are pulled to the poles
Meiosis I
Prometaphase
- Spindle fibers starting to attach to the chromosomes through its centromeres
- The chromosomes continue to condense
What are diploids?
- two sets of chromosomes (2n)
- In humans, 23 pairs or 46 chromosomes in total
- In this checkpoint, the DNA is examined for errors
- If errors are detected, the cell attempts to complete replication or repair damaged DNA in this checkpoint
- If the damage is irrepairable, the cell may undergo through apoptosis (cell suicide) to avoid replication of damaged DNA
G2 Checkpoint
What happens in Gap 2 (G2)?
- Preparation for Mitosis
- Organelles are replicated
- More growth occurs
Why does the activity of cyclin-dependent kinases fluctuate during the cell cycle?
Because they are controlled by cyclins, so named because their concentrations vary with the cell cycle.
Difference of Mitosis and Meiosis
- Meiosis produces n while mitosis produces 2n
- Daughter cells produced through mitosis are genetically identical, opposite to meiosis
- In meiosis, division occurs twice but replication only once
Meiosis II
Telophase II and Cytokinesis II
- The cells split in half
- Four non-identical haploid daughter cells are produced from one original diploid cell
What is synapsis?
pairing of homologous chromosomes forming a tetrad (4 homologous chromatids or 2 homologous chromosomes)
Cell Division vs Nuclear Division
What is cytokinesis?
The actual division of cells into two new cells
This checkpoint checks if all the sister chromatids are correctly attached to the spindle microtubules
M Checkpoint (Spindle Checkpoint)
What is haploid?
- One set of chromosomes (n)
- Gametes or sex cells
- In humans, 23 chromosomes
Mitosis
What happens in metaphase?
- Chromosomes are pulled to the center of the cell
- They line up along the “metaphase plate”
What does G1 checkpoint check before giving a go-signal?
- Cell size (is the cell large enough to divide?)
- Nutrients (Does the cell have enough energy reserves or available nutrients to divide?)
- Molecular signals (Is the cell receiving positive cues (such as growth factors) from neighbors?)
- DNA integrity (Is any of the DNA damaged?)
Why do cells divide?
For reproduction, growth and repair of damaged cells
Identify
Sequence of phases in the life cycle of a cell
Cell Cycle
What causes variation?
- Crossing over in Prophase I
- Independent Assortment in Meta I and II
- Random Fertilization
Meiosis I
Prophase I
- Chromosomes condense
- Homologous chromosomes pair with each other
- Each pair contains four sister chromatids (tetrad)
Difference between cytokinesis in Plant and Animal cells
Animals: pinching of plasma membrane
Plants: The cell elongates and the cell plate forms (future cell wall and cell membrane)
- The checkpoint wherein the cell decided whether or not to divide
- Once passed through, it becomes irreversibly committed to division
G1 Checkpoint
Homologous Pair
- each chromosome in the pair are identical (carrying genes for same trait)
- only one pair differs; sex chromosomes (x or y)
What is centromere?
The point where sister chromatids are joined together
Crossing Over
chromatids of tetrad exchange parts
What is meiosis?
- Nuclear division that produces four daughter cells with half the number of chromosomes of parent cell
- Important in sexual reproduction
- Involves combining genes of parents to produce a genetically distinct individual
Meiosis I
Telephase I and Cytokinesis I
- Daughter nuclei formed (haploid n)
The two types of regulatory proteins that are involved in cell cycle control
Cyclins and Cyclin-dependent Kinases (Cdks)
Mitosis
What happens in Prophase?
- Chromosome condenses
- Microtubules form
- The nuclear envelope breaks down
What are the different periods under interphase and mitotic phase?
Interphase
* Growth (G1)
* Synthesis (S)
* Growth (G2)
Mitotic Phase
* Mitosis
* Cytokinesis
Meiosis II
Prophase II
Spindle fibers form again
Mitosis
What happens in Anaphase?
- Centromeres divide
- Spindle fibers pull one set of chromosomes to each pole
- Precise alignment is critical to division
Spermatocytogenesis vs Spermiogenesis vs Spermatogenesis
Spermatocytogenesis: Process of producing 4 spermatids (Meiosis I + Meiosis II)
Spermiogenesis: Converting spermatids to spermatozoa
Spermatogenesis: Spermatocyto + Spermio; starts at puberty
Mitosis
What happens in telophase?
- Nuclear envelope forms around chromosomes
- Chromosomes uncoil
- Cytokinesis
What is mitosis?
A type of cell division in which a mother cell divides to produce two new daughter cells that are genetically identical to itself.
In the context of cell cycle, it is the part of the division process in which the DNA of the cell’s nucleus is split into two equal sets of chromosomes.
True or False
Cells sometimes undergo mitosis without going through cytokinesis
True
Meiosis I
Metaphase I
- Tetrads or homologous chromosomes move to the center of the cell
- Independent assortment occurs
Meiosis I
Anaphase I
Homologous chromosomes are pulled to opposite poles
What is chiasmata?
The point of intersection during crossing over
True or False
DNA is replicated for the second time in Meiosis II
False. No replication occurs during Meiosis II
A cyclin-cdk complex that triggers a cell’s passage past the G2 checkpoint into the M phase.
MPF (maturation-promoting factor)
What are sister chromatids?
Identical structures that result from chromosome replication, formed during S phase
Mitosis
What happens in Prometaphase?
- Nuclear envelope breaks down
- Chromosomes attach to the mitotic spindle
What does G2 checkpoint check before giving a go-signal?
- DNA integrity (Is any of the DNA damaged?)
- DNA replication (Was the DNA completely copied during S phase?)
Meiosis II
Metaphase II
Sister chromatids move to the center
What is chromatin?
Thin, fibrous form of DNA and proteins
