Cell Structure - Cell Replication Flashcards
What are the three stages of the cell cycle?
- interphase = chromosomal replication and cell growth
- nuclear division = stages of mitosis (or meiosis)
- cytokenises = division of the cytoplasm
What does mitosis produce?
Two daughter cells that have the same chromosomes as the parent cell as well as each other
What happens at interphase?
- there is de-condensed chromatic in the nucleus
- nucleoli are visible
- the nuclear membrane is visible
- centrioles are present
- the DNA undergoes replication and the two sister chromatids remain joined at the centromere
what happens at prophase?
- chromatin condenses and chromosomes become visible
- nucleoli disappears
- the nuclear membrane disappears
- the centrioles move to the poles off the cell and each centriole forms spindle fibres to produce the spindle apparatus
- the chromosomes attach to the spindle fibres at their centromeres
In prophase of mitosis, how do you know centrioles are not essential to spindle fibre formation
As plant cells lack centrioles yet still develop the spindle apparatus
What happens at metaphase?
- the chromosomes can be seen to be made of two chromatids
- the microtubules of the spindle apparatus are attached to the centromere of each chromosome
- the chromosomes are pulled along the spindle apparatus and arrange themselves across the equator of the cell
What happens at anaphase?
- the centromeres divide and the spindle fibres begin to shorten
- sister chromatids are pulled to opposite poles by the spindle fibres using energy from ATP
- the separated chromatids are now referred to as individual chromosomes
What happens at telophase and cytokinesis ?
- the chromosomes reach the poles and de-condense making them no-longer visible to leave the widely spread chromatin
- the spindle breaks down and the centrioles reappear
- the nuclear membrane and nucleoli reappear
- the cytoplasm divides in cytokinesis to form two identical daughter cells
What are the three sub phases of interphase?
- G1 = growth
- S= DNA synthesis
- G2= preparation and growth for mitosis
On a graph, how can you determine where the S phase of interphase is happening?
By looking at where the amount of DNA in the cell doubles
In what stage of the cell cycle do chromosomes become visible in the cell?
After the DNA has been replicated in interphase so at the start of prophase the chromosomes become visible
What is mitotic index?
The % of cells that are in mitosis
How do you calculate the mitotic index?
Mitotic index = # of cells in mitosis / # of total cells
Around how much of the time a mammals cell cycle takes is interphase?
90%
What is cancer? What is it a result of?
A group of diseases (around 200 in total) caused by a growth disorder of cells as a result of damage to the genes that regulate the cell cycle and mitosis