Mitosis Flashcards
what are the three phases of the cell cycle
- interphase
- nuclear divison(mitosis)
- cytokinesis
what happens during interphase
the cell increases in mass and size for cell division by synthesising proteins and replicating its DNA
what are the 3 phases interphase consists of
- g1 phase
- s phase
- g2 phase
explain the G1 phase
Cells make the RNA, enzymes and other proteins required for growth
explain the S stage
- the DNA in the nucleus replicates by semi-conservative replication resulting in each chromosome consisiting of two identical sister chromatids
explain the G2 phase
- the cell continues to grow in preperation for mitosis
- microtubules are produced which form the mitotic spindle
what are the 4 stages of mitosis
- prophase
- metaphase
- anaphase
- telophase
explain 3 ways that mitosis is fundamental to biological processes
- growth of multicellular organisms - mitosis enables zygotes to grow into multicellular organisms
- replacement of cells and repair of tissues - damaged tissues can be repaired by mitosis
- asexual reproduction - the offspring are genetically identical to the parent
explain what happens during prophase
- chromosomes condense and are now visible
- two centrioles move towards opposite poles of the cell
- spindle fibres begin to emerge from the centrioles
- the nuclear envelope breaks down
explain what happens during metaphase
- chromosomes line up at the equator of the cell
- chromosomes attach to the spindle fibres by their centromers
explain what happens during anaphase
- spindle fibres shorten and centromere splits
- this pulls the sister chromatids to opposite poles of the cell
explain what happens during telophase
- chromosomes arrive at opposite poles nd begin to uncoil
- the spindle fibres break down
- nuclear envelope begins to reform around each set of chromosomes
explain what happens during cytokinesis
- the cytoplasm divides forming two genetically identical cells
what is the formula to calculate mitotic index
mitotic index = number of cells with visible chromosomes / total number of cells
what is cancer
uncontrolled mitosis
a changes in the base sequence of a gene is known as a _______
mutation
what are carcinogens
- any agent that may cause cancer
some tumours do not spread from their original site, these are known as _____
benign
* they do not cause cancer
some tumours spread through the body, invading and destroying other tissues. These are known as _____
malignant
what is the process of cell division in prokaryotic cells called
binary fission
explain the process of binary fission
- the single, circular DNA molecule undergoes DNA replication
- any plasmids present undergo DNA replication
- the parent cell divides into two cells, with the cytoplasm roughly halved
- the two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids