Mitosis
What are the 4 stages of mitosis? (In the order they occur)
Prophase, Metaphase, Anaphase, Telophase
What is the end result of meiosis?
4 genetically unique haploid cells
1 cell, chromosomes align on the equator
Metaphase (mitosis)
What holds sister chromatids together and is where the microtubules attach?
centromere/kinetochore
What are the two phases of the cell cycle?
Interphase and M-phase
If the parent cell has 25 chromosomes, how many chromosomes are present in the cell after S phase?
50
What separates in meiosis I vs. in meiosis II?
Meiosis I: homologous chromosomes separate
Meiosis II: sister chromatids separate
Nuclear membrane breaks down, spindle forms, centrosomes move to opposite poles, homologous chromosomes free floating in cytosol
Prophase 1
define sister chromatid
sister chromatids are duplicated chromosomes (therefore genetically identical to each other) that are present during cell division (mitosis or meiosis)
What occurs during G1, S, and G2 of interphase
G1: cell grows, begins duplication of organelles
S: cell duplicates the DNA
G2: cell finishes growing and duplicates remaining organelles
How does plant cell cytokinesis differ from animal cell cytokinesis?
Plant cell: cell wall forms by the fusion of carbohydrate rich vesicles in the equitorial plane of the cell, fusion moves outwards towards the cell wall
animal cell: microtubule wraps around the equitorial plane of the cell and contracts to form the cleavage furrow, continued contraction results in the two cells pinching off
Random Assortment, Random Fertilization, Crossing Over
Anaphase 2 of Meiosis
How do oncogenes have the ability to cause cancer?
Mutations in either proto-onocogenes or tumor suppressor genes can cause cancer. Overexpression of protooncogenes results in uncontrolled cell proliferation whereas underexpression of tumor supressor genes blocks cell cycle checkpoint mechanisms and allows a cell with mutated DNA to divide
What occurs during G0?
During G0, the cell is still metabolically active but not dividing
Calculate the mitotic index of the following data:
# of cells in interphase: 80
# of cells in prophase: 20
#of cells in metaphase: 40
# of cells in anaphase: 25
# of cells in telophase: 35
120/200 = 0.6
Anaphase 1 and Anaphase 2
Haploid chromosomes align along equator
Metaphase 2
What is the relationship between maternal age and probability of non disjunction?
there is a strong correlation between maternal age and the occurrence of non-disjunction events
this evidenced by a higher rate of chromosomal abnormalities in offspring conceived at older maternal ages
What are the 3 cell cycle checkpoints?
G1, G2, and Metaphase checkpoints
Contrast the 4 events that occur in prophase and telophase
1. In prophase, DNA condenses (supercoils); in telophase, DNA unwinds
2. In prophase, the nuclear membrane breaks down; in telophase, the nuclear membrane reforms
3. In prophase, the centrosomes move to opposite poles of the cell; in telophase, centrosomes break down
4. In prophase, the spindle forms; in telophase, the spindle dissolves
During what phase does crossing over occur and what phase does random assortment occur?
Crossing Over: Prophase 1
Random Assortment: Metaphase 1
How does non disjunction result in chromosomal abnormalities?
The failure of chromosomes to separate may occur via:
This separation failure leads to abnormal chromosome numbers in gametes
How does the cyclin-CDK interaction control cell cycle progression?
Each Cyclin-CDK complex has a specific target protein that when interacted with, triggers an action for that specific stage of the cell cycle
Different cyclins specifically bind to, and activate, different classes of cyclin dependent kinases
Cyclin levels will peak when their target protein is required for function and remain at lower levels at all other times