HRR: mitosis Flashcards
What are the stages of Mitosis
prophase, metaphase, anaphase, telophase
At which point are there 2 chromosomes consisting of sister chromatids?
After G2
Sister chromatids become separated and divided into cells during…
mitosis
The M phase is controlled by…
CDK1/cyclin B
Describe prophase, including its key events
Chromosomes condense but sister chromatids are still held together. The centrosomes move to opposite poles and the mitotic spindle forms. The nuclear envelope breaks down and disappears, and microtubules that make the mitotic spindle can attach to kinetochores
Which proteins are associated with condensation of chromosomes
Condensins and histones H3 and H1
Which proteins are involved in formation of mitotic spindle
MAPs (centrosome and microtubule associated proteins)
Which proteins are involved in breakdown of nuclear envelope
Lamins, nuclear pore complexes, inner nuclear membrane proteins
What are cohesions
A family of proteins that bind DNA during the S phase and hold sister chromatids together by creating interstrand cross-links; they’re still present at the centromere during prophase and metaphase
What are condensins
They produce intrastrand cross-links to condense the chromatin. they’re mostly active in prophase
Describe the breakdown of the nuclear envelope
Cyclin B/CDK1 phosphorylates Lamins to cause depolymerization of nuclear lamina. Proteins in the nuclear pore also get phosphorylated and the complexes are disrupted. The inner nuclear membrane becomes phosphorylated, and it detaches from B type Lamins.
When are Lamins dephosphorylated
Telophase
Describe formation of the mitotic spindle
Cyclin B/CDK1 activation triggers migration of centrosomes to opposite poles. MAPS anchor negative ends of microtubules in the pericentriolar material, which can then grow from the plus end via polymerization of tubulin toward the metaphase plate. This results in forming the mitotic spindle.
What are Kinetochores
They’re proteins bound at the centromere that serve as attachment site for microtubules of the mitotic spindle. When chromatids are separated, they act as motors to facilitate movement along microtubules toward the centrosome.
Describe the structure of Metaphase Chromosomes
They’re very short due to the condensins and contains cohesions at the centromere. They can be metacentric (equal q and p arms), submetacentric (unequal p and q arms) or acrocentric (super small p arm)
