Cell Division, Diversity And Organisation Flashcards
(28 cards)
Definition of meiosis
Process of nuclear division that results in the formation of cells containing half the number of chromosomes
Definition of mitosis
Process of nuclear division where two genetically identically nuclei are formed from one parent cell
Comparing meiosis and mitosis: mitosis
Genetically identical 2 daughter cells produced Occurs in all animal cells and only in meristem cells No crossing Asexual reproduction 2 cells produced 46 chromosomes (number stays the same) Repairs cells
Comparing mitosis and meiosis: meiosis
Genetically varied 4 daughter cells produced Occurs in sex cells Crossing sometimes occurs Gametes created Sexual reproduction One nuclear division separating choromosomes 23 chromosomes (haploid cells produced)
Stages of mitosis
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
Why do yeast cells not produce the calculated number of potential new cells?
Mutations can occur
Bugles do not form exactly side to side
Prophase
- Chromosomes condense
- Chromosomes can be seen at the centromere
- Nuceoli dissapears
- Nuclear membrane breaks down
- Spindle apparatus appears
Metaphase
- Centromeres of chromosomes line up at equator
- Spindle apparatus is fully formed
- Sister chromatids are connected to either pole
Anaphase
- Centromeres seperate
- Chromatids are drawn to either pole
- The movement is brought about by the lengthening of pole-pole microtubules and the shortening of pole-chromatid microtubules
Telophase
- Daughter cells reach either pole
- Nuclear membrane and nucleoli reform
- Spindle apparatus disappears
Cytokinesis (animal cells)
- Can occur after or during telophase
- Animal cells form a cleavage furrow where the cell is pinched off in two
Cytokinesis (plant cells)
- Membrane bound vesicle containing cell wall material collect at the middle point
- Vesicles join to form a cell plate
- The cell plate extends to fuse with the plasma membrane, thus dividing the cells
Binary fission
- Daughter cells are cloned
- DNA is circular and plasmids replicated, producing exact copies
- DNA is shared between daughter cells
- Not mitosis
- A colony of cells is produced by one single cell
Budding yeast
- Produces genetically identical cells
- Nucleus divides
- Cell bulges on one side
- Bulge contains cytoplasm, organelles and one of the nuclei
- Bulge pinches off forming a cell wall around a new separate cell
Stem cells
Undifferentiated cells that have the potential capability of becoming any one of the cell types in a fully grown organism
Clones
Genetically identical cells or individuals
Interphase
- DNA replicates
- DNA is decondensed so chromosomes are not visible
- Nuclear membrane and centrioles visible
Importance of producing new cells
- Asexual reproduction
- Growth
- Repair
- Replacement
Process of mitosis
- Chromosomes become visible
- Nuclear envelope breaks down
- Centrioles move to either pole and form a spindle
- Chromosomes line up at the equator
- Replicated sister chromatids split by their centromeres and move away towards the poles attached by their centromeres
- Nuclear envelopes surrounds new sister chromatids
- Spindle apparatus breaks down
- Cytokinesis takes place
The cell cycle
Describes the events that take place as one parent cell divides to produce two new daughter cells which then each grow to full size
Steps of the cells cycle
M – nuclear division (mitosis) + cytokinesis
G1 – Biosynthesis (proteins made, organelles replicated
S – Synthesis of new DNA (replication of new chromosomes
G2 – Growth
Why can supercoiled chromosomes only be coiled for a short time
Supercoiled chromosomes can’t perform their normal functions in the cell so they need to be uncoiled
How are cells in a multicellular organism organised?
- A group of specialised cells work together to form a tissue
- Groups of tissues carry out many processes to form an organ
- A group of organs that carry out a common process work together to form a organ system
- Cells differentiate to specialise in a specific function
Processes that occur during interphase
- Cell growth (creation of organelles)
- Protein synthesis
- ATP production
