Cell Division
Why do unicellular organisms undergo cell division?
Reproduction
What are the three checkpoints?
G1, G2, and M
What is each part of this structure called? Photo 1
Red: chromosomes
Blue:centromere
Green: chromatid
Where does DNA replication occur within mitosis and meiosis?
Mitosis: during interphase, before mitosis
Meiosis: During interphase before meiosis I but not meiosis II
How many chromosomes do humans have?
23 pairs... 46 total
Why do multicellular organisms undergo cell division? 4 answers
Development
Growth
Repair
Renewal
Which checkpoint is the main checkpoint and why?
G1 checkpoint, its the cell cycle main checkpoint because if it passes, the cell is dedicated to dividing if the proper resources are present.
Photo 2. What stage is depicted?
Metaphase
In which does synapsis of homologous chromosomes occur?
Meiosis, during prophase 1
How many chromosomes are there in prophase? How many chromatids?
46 chromosomes 92 chromatids
What is the cell cycle composed of and what happens during those parts?
Interphase (cell growth and prep for cell division) and mitotic phase (mitosis and cytokinesis)
What is the importance of the M checkpoint?
Spindle checkpoint!
Photo 3. What phase is depicted here?
Prophase
How many division occur in each?
One in mitosis and two in meiosis
How many chromosomes in anaphase? What about chromatids?
92 chromosomes. 92 chromatids.
Where is most of the cell cycle spent?
In interphase
What will happen if the DNA is found to be damaged and cannot be prepared at the M checkpoint? What about at the G1?
Apoptosis will occur.
If G1, the cell will enter G0 (holding phase)
Photo 4. What is being depicted here?
Cytokinesis in plant cells...The formation of a new cell wall in a plant cell.
What kind of cells can mitosis occur in? What about meiosis?
Mitosis-diploid and haploid
Meiosis- diploid
How many chromosomes are present in a daughter cell after meiosis I? Chromatids??
23 chromosomes, 46 chromatids.
What controls the cell cycle?
Checkpoints and external factors like hormones.
What are the three extracellular signals discussed in lecture?
1. Growth factors
2. Density-dependent inhibition
3. Anchorage dependence
What are the little blue things on either side of the chromosome? What about the lines? And what are they composed of?
Centrosome (aster), spindle fibers, composed of microtubules.
Mitosis- 2 daughter cells, each genetically identical and same chromosome number with parent
Meiosis- 4 daughter cells, each haploid (n), genetically different from the parent cell and from each other (bc crossing over)
How many chromosomes and chromatids are present in a cell in anaphase I and what about anaphase II?
Anaphase I: 46 chromosomes and 92 chromatids
Anaphase II: 46 chromosomes and 46 chromatids