2.2 All cells arise from other cells Flashcards
What is the cell cycle?
The regulated sequence of events that occurs between one cell division and the next.
What are the 3 phases of the cell cycle?
Interphase, nuclear division (mitosis), cytokinesis.
What happens during interphase?
Organelles double, cell grows and DNA replicates.
What are the phases of interphase?
G1, S, G2.
What happens during the G1 phase?
Growth.
What happens during the S phase?
DNA synthesis.
What happens during the G2 phase?
Growth and preparation for mitosis.
What is a chromosome during mitosis?
2 chromatids attached by a centromere.
What are the 4 stages of mitosis?
Prophase, metaphase, anaphase, telophase.
How many divisions are there in mitosis?
1.
What does mitosis produce?
2 genetically-identical daughter cells.
What is the purpose of mitosis?
Growth and repair.
What happens to the chromosomes during prophase?
Chromosomes condense and become visible.
What happens to the centrioles during prophase?
Centrioles separate and move to opposite poles of the cell.
What happens to the chromosomes during metaphase?
They line up along the equator of the cell.
What happens to the spindle fibres during metaphase?
They are released from poles and attach to the centromere and chromatid.
What happens to the spindle fibres during anaphase?
They retract.
What happens to the centromere during anaphase?
It divides in 2.
What happens to individual chromatids during anaphase?
They are pulled to opposite poles.
Name the three phases of mitosis shown by C, D and E on the figure above.
Describe the role of the spindle fibres and the behaviour of the chromosomes during each of these phases.
C = prophase
D = metaphase
E = anaphase
(5)
- in prophase, chromosomes condense
- in prophase/ metaphase, centromeres attach to spindle fibres
- in metaphase, chromosomes line up at the equator of the cell
- in anaphase, centromeres divide
- in anaphase, chromatids are pulled to opposite poles of the cell
What does anaphase require?
ATP.
What happens to the chromosomes during telophase?
They decondense.
What happens to the spindle fibres during telophase?
They disintegrate.
Mitosis is important in the life of an organism.
Give two reasons why. (2)
growth/increase in cell number
- replace cells/repair tissue