Cell Division Flashcards
What is the cell cycle?
Events that take place as one parent cell divides to produce 2 new daughter cells, can be life cycle for some organisms
Where are chromosomes and what do they contain?
In the nucleus of eukaryotic cells, contains 1 mol of DNA including specific lengths: genes
How many chromosomes in the nucleus of human cell?
46
Before a cell can divide, what must happen?
DNA from each chromosome must be replicated, stay held together at the centromere
What are the DNA replicates called?
Pair of sister chromatids, cant be seen under a light microscope
What happens to sister chromatids when the cell divides?
Each one will end up in a different new daughter cell
What does the super coiling of the chromatids do?
Forms visible chromosomes, each is then short and sturdy enough to moved around more easily, can be stained and seen under light micrscope
How thick are the chromatid threads before and after coiling?
30nm thick to 500nm thick
What cant super coiled chromatids do? How long should they be super coiled?
Chromosomes cant perform normal function so need to be coiled for shortest amount of time
What are daughter cells?
Genetically identically to each other and the parent cell
What happens when the chromosomes are being replicated?
Proof reading enzymes move along the new DNA strands and check that copying was successful
What can happen if genes aren’t copied properly?
Mutations, new cells may not function
How fast is the cell cycle?
Varies between species and cell type, availability of nutrients
What are the 4 stages to the cell cycle?
interphase: DNA replicates, mitosis: nucleus divides and chromatids separate, cytokineses: cytoplasm divides/cleaves, growth phase: each new cell grows to full size
What are G1 and G2?
G1: biosynthesis (proteins and organelles made)
G2: growth
What do the new daughter cells also need?
Membranes, cytoplasm, organelles, enzymes and other proteins
Mitosis definition?
process of nuclear division where 2 genetically identical nuclei are formed from one parent cell nucleus
Why do new cells need to be made?
Asexual reproduction: to produce new organisms, multicellular organisms grow by producing new cells, damaged/dead cells need to be replaced (RBCs and skin cells)
In what order are the 4 stages of mitosis?
- prophase, 2. metaphase 3. anaphase 4. telophase
What happens in prophase?
Replicated chromosomes shorten and thicken (super coil), nuclear envelope breaks down, centriole divides in 2 and moves to opposite poles of cell forming spindle
What happens in metaphase?
Chromosomes move to equator of spindle and becomes attaches by its centromere
What happens in anaphase?
Sister chromatids are separated when their centromere splits, each of the ‘sisters’ is an individual chromosome again. Spindle fibres shorten again pulling sisters towards the poles (they are a v-shape, centromere pulls them)
What happens in telophase?
As the sister chromatids reach each pole, anew nuclear envelope forms around each set. Spindle breaks down and chromosomes uncoil
What is cytokinesis?
whole cell splits into 2 new cells (after telophase)
3 differences between the cell cycle in animals and plants?
Only meristem cells in plants can divide by mitosis and cytokinesis, plant cells don’t have centrioles (tubulin protein threads made in cytoplasm), in plants cytokinesis starts with formation of cell plate
