Unit 3- Eukaryotic Cell Division Flashcards
What is chromatin?
- coiled DNA wrapped around a histone protein
How is chromatin different to chromosomes
Chromatin are bundles of histone proteins wrapped in DNA
Chromosomes are millions of coiled up chromatins
Where are chromatids joined?
At the centromere
Why can we see chromosomes in a light microscope?
They are short very wide bundles of chromatin that are so thick and coiled we can see them
What is the product of mitosis?
2 genetically identical daughter cells
What is mitosis used for?
- Growth
- replacement
- repair
- asexual reproduction in some eukaryotic organisms
- artificial cloning of plants and animals
What are the 3 phases of the cell cycle?
Mitosis
Cytokinesis
Interphase
What phase do cells spend the majority of their time in?
Interphase
Describe interphase:
Growth 1 phase: cell grows to original size, organelles are replicated and genes are expressed
Synthesis phase: DNA and histone are replicated
Growth 2 phase: spindle and proteins are synthesised
Summary of mitosis phase:
Nucleus divides to make 2 nuclei with identical copies of DNA
This is subdivided into PMAT
Summary of cytokinesis:
The division of the cytoplasm to form 2daughter cells, with 1 nucleus each
Prophase: (3)
- Chromosomes condense becoming visible
- centrioles move to opposite poles of cell
- nucleoli disappears
Metaphase:
- nuclear envelope disappears
- chromosomes align along equator of cell
- spindle fibres connect centrioles to chromosomes
Anaphase: (3)
- centromere splits, chromatids separate
- spindle fibres shorten pulling chromatids towards poles, centromere first
- some spindle fibres lengthen pushing the poles further apart
Telophase: (3)
- spindle fibres disperse
- nuclear envelope forms around 2 sets of chromosomes
- chromatids (chromosomes) uncoil becoming too thin to see
Cytokinesis, how it differs in plants and animals:
Animals: ring of actin filament forms around cell equator and tightens squeezing the cell into cleavage furrow which splits into 2 cells
Plants: vesicles move to cell equator, line up and fuse a cell plate down the middle which developers into a cell wall