Lecture 14: Mitosis and Meiosis Flashcards
What are the six phases of mitosis?
- Interphase
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
What is interphase?
Everything that is not mitosis(G1, S, G2)
What occurs during interphase?
DNA is spread out, Centrosomes are duplicated(G2)
What happens during prophase?
-Chromosomes condense(chromosome refers to two chromatids)
-Spindle forms
-Kinteochores
-Centrosomes move to opposite ends of the nucleus
What are centrosomes?
Microtubule organizing centres
What happens during prometaphase?
-Nuclear envelope breaks(surrounds chromosomes originally)
-Microtubules probe the cytoplasm and begin attaching to kinetochores
-Microtubules form
What happens during metaphase?
-Centromeres of chromosomes become aligned in a plane in the cell’s equator due to tension caused microtubules bound to the kinetochores
-Sister chromatids bound to kinetochore microtubule on opposite spindles
What happens after metaphase? (hint: not anaphase)
Cell has a checkpoint to ensure that all of the chromosomes are correctly lined up
What happens during anaphase?
-Centromere that was holding the sister chromatids together separates
-The microtubules shorten pulling the sister chromatids apart
-Spindle Elongates
How are the sister chromatids pulled apart during anaphase?
Each sister chromatid is attached to a microtubule, that applies tension to the sister chromatid and forces the sister chromatids apart
What happens during telophase?
Daughter chromosomes are brought to the poles of the cell and decondense,
-nuclear envelope reforms
-microtubules dissolve
-Spindle breakdown
What do the microtubules bind to ?
Kinetochores of chromosomes
-Microtubules can also bind to each other
What is a mitotic spindle?
The mitotic spindle is the macromolecular machine that segregates chromosomes to two daughter cells during mitosis
True or False: Sister chromatids must remain paired until all chromatids are attached to a kinetochore microtubule
True
Explain the probing of microtubules
Microtubules grow and shrink from the centrosome, probing the cytoplasm. Microtubules do not become stable until they reach a kinetochore.
Can microtubules from the same spindle connect to the same kinetochore of the same chromosome?
No
When are the centrosomes of the sister chromatids allowed to dissolve?
Once all sister chromatids have been captured by microtubules then their centromeres are allowed to dissolve
Is cytokinesis the same in plants and animals?
No
How is cytokinesis done in animals?
-Via purse string mechanism
-A ring of actin and myosin forms in the middle of the cell and then it begins to contract until it pinches off the cell(actin-myosin contraction)
How is cytokinesis done in plants?
-Vesicles with cell wall material segregate in between the two cells and form a new wall between the two nuclei
Does cytokinesis need to occur? I not in what cells does it not occur in?
-No its does not need to occur
- In muscle cells, cells will undergo mitosis but not cytokinesis these cells have more than usual number of chromosomes
What is sex?
Mixing of the genetic material of two organisms
What must happen before sex?
Before sexual reproduction you must reduce the number of homologs by half
Are homologous chromosomes haploid or diploid?
Haploid(n)