Cells Alive 5: Cell Division Flashcards
What occurs during Interphase in cell divison?
The cell grows and the protein content doubles, the organelles double in size- in the S-phase DNA is synthesised, the centrosme repicaltes
What si the first stage of metaphase?
Prophase
What occurs during prometaphase?
1 Nuclear envelope breaks down…
…which allows microtubules access to
the chromosomes
2 Chromosomes attach to the
microtubules via kinetochore complex
(This interaction will pull the chromosome
apart during cell division)
What occurs during Prophase?
1 Chromosomes condense
2 Mitotic spindle (microtubules and
associated proteins polymerise) forms
3 Centrosomes move apart
4 Protein complex (kinetochore) forms at
centromere of the chromosome (the bit
where the two arms meet)
What occurs during Metaphase?
1 Chromosomes align at the equator
2 Sister chromatids attach to opposite poles
by kinetochore microtubules
What occurs during Anaphase?
1 Cohesive link between sister chromatids is released
2 Kinetochore microtubules shorten
3 Centrosomes move apart
So the sister chromatids are pulled to opposite ends of the cell
What occurs during Telophase?
1 Daughter chromosomes reach the poles
2 New nuclear envelope forms from fragments
attached to individual chromosomes
Therefore two nuclei
3 Contractile ring begins to form
around the equator
What do the kinetochore microtubules do?
Attach to the chromosones
What do teh mcirotubules do during prometaphase?
They grow and shrink as they try and find a target
What do the microtubules do during metaphase?
motor proteins (+ & - ) pull
chromosomes around until they are aligned
What occurs during anaphase?
kinetochore microtubules shorten &
motor proteins move the chromatids towards the
centrosome – actively separate the two chromatids –
genetic material is split in the two new cells
How is actin involved with ctokinesis?
involved in ring contraction
Where is the restriction point?
at the end of G1
What is the purpose of the restriction point?
- growth factor interacts with cell surface receptor
- triggers intracellular signalling pathway
- activates a transcription factor called Myc
- turns on genes that promote entry into mitosis
What is the kinetochore?
The protein complex at the centre of the chromosome
What do the nuclear lamina need to do before mitosis?
They need to disassemble
What do the kinetochore microtubules do during prometaphase?
grow and shrink until they can find a target
What do the kinetochore microtubules do during metaphase?
motor proteins pull chromosomes around until they are aligned
What do the kinetochore microtubules do during anaphase?
They shorten and motor proteins move the chromatids towards the centrosome
What does Myc do?
Turns on genes that promote entry into mitosis
what are cdk’s?
there are 4 classes of them, their activity oscillates during the cell cycle- phosphorylate proteins modulate major events in the cell cycle
What are cyclins?
they bind and activate cdk’s
What is leptotene?
The first stage of prophase 1 in meiosis, when the chromosomes condense
What is zygotene?
The second stage of prophase 1 in meiosis, when the homologous chromosomes align
What is pachytene?
The third stage of meiosis prophase 1, when the chromosomes cross over
What is Diplotene?
The fourth stage of meiosis 1, synaptonemal complexes break
down; pairs of chromosomes linked at
crossover points (chiasmata)
What is diakinesis?
The last stage of Prophase 1 in meiosis, the chromosomes condensation reaches a maximum
