Cell Division Flashcards
What is contact inhibition of cell growth?
Cells grow normally by detecting neighbouring cells
What happens during the three stages of interphase?
G1 – the cell makes sure that it has everything that is necessary for duplication
S – DNA replication, protein synthesis and replication of organelles
G2 – the cell checks that everything is ready to enter mitosis
What are centrosomes and what do they consist of?
Centrosomes are organelles near the nucleus of a cell, which contain centrioles (mother and daughter), and from which spindle fibres develop in cell division
What happens to the centrosomes during G1 and S?
The mother and daughter centrioles separate in G1
Then the mother produces another daughter and the daughter produces another mother, resulting in the formation of 2 centrosomes (the duplication takes place during S phase)
What are the points around the centrosome from which microtubules arise?
Nucleating sites
NOTE: nucleation is the assembly of microtubules
Describe the condensation of chromatin that takes place duringprophase.
Chromatin condenses around nucleosomes to form chromosomes
What is a kinetochore?
Protein complexes that are attached to each sister chromatid – they are important in detecting the attachment of microtubules
Describe the arrangement of centrosomes at the end of prophase.
They are on opposite sides of the nucleus
What happens in initial spindle formation
Radial microtubule arrays form around the centrosomes which begin to grow towards other centrosomes
What is formed when radial microtubule arrays from the two centrosomes meet in the middle?
Polar microtubules
What happens to the sister chromatids as soon as they are captured by microtubule arrays from both centrosomes?
They slide towards the middle of the cell
What keeps the sister chromatids stuck together?
Cohesin (protein complex)
What happens in anaphase A?
Cohesive broken down and microtubules become shorter so daughter chromosome pulled towards opposite pole
What happens in anaphase B?
Daughter chromatids continue to migrate towards the poles
The centrosomes migrate apart
Describe what happens in telophase.
Daughter chromatids arrive at the pole and the nuclear envelope reassembles
Assembly of a contractile ring of actin and myosin filaments where the cells are going to split
The contractile ring squeezes the cell so it divides into two daughter cells
NOTE: cleavage furrow = where the cell is going to be cleaved