what is cell growth and division important for?
- Increasing population size (single-celled organisms)
- Growing new tissues (e.g. new leaves during plant development)
- Asexual reproduction (bacteria, fungi, corals, many others)
- Replacement of lost cells (lining of gut) and/or damaged cells (wound repair)
what is binary fission ?
- Involves coordinated cytoplasmic growth, DNA replication, and cell division
- Results in two daughter cells from an original single parent cell
- DNA replication occupies most of the cell cycle in rapidly dividing prokaryotic cells
what is The Bacterial Cell Cycle?
Replication of the bacterial chromosome
consumes most of the time in the cell cycle
where does the bacterial cycle begin?
single site called the origin of replication (ori) through reactions catalyzed by enzymes located in the middle of the cell
Mitotic Cell Division
Eukaryotes : Genome: multiple, large, linear chromosomes , DNA in nucleus
Prokaryotes : Genome: one small, circular chromosome ,
DNA in cytoplasm
what is the cell cycle?
A period of growth followed by nuclear division and cytokinesis
what is the purpose of mitosis?
divides replicated DNA equally and precisely
* Ensures the two cells resulting from a cell division have the same genetic information as the parent cell entering division
Mitosis is the basis for ?
- Growth and maintenance of body mass in multicellular
eukaryotes - The reproduction of many single-celled eukaryotes
how is the DNA of eukaryotic cells divided?
divided among individual, linear chromosomes
number of chromosome sets of a cell or species is called
Ploidy
Haploid
a cell with one complete set of chromosomes
Diploid
a cell with two complete sets of chromosomes
what are sister chromatids ?
Replication of DNA of each individual chromosome
creates two identical molecules
Chromosome segregation
Equal distribution of daughter chromosomes to each of two cells resulting from cell division
phases of the eukaryotic cell cycle
interphase , prophase, metaphase, anaphase, telo phase
what is interphase?
is the first stage of the cell cycle; it begins immediately
after mitosis (& cytokinesis) and continues until the beginning of the next mitosis
three phases of interphase
- G1 phase: The cell carries out its function(s), and in
some cases grows, during this initial “gap” phase - S phase: DNA replication and chromosome
duplication occur - G2 phase: A second “gap” in the cell cycle when cell
growth continues and the cell prepares for mitosis
and cytokinesis
mitotic cell cycle :
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Stage 1: Prophase
- Chromosomes condense into compact, rod-like structures
- Spindle forms in the cytoplasm
Stage 2: Prometaphase
- Nuclear envelope breaks down
- Spindle enters former nuclear area
- Microtubules from opposite spindle poles attach to two kinetochores of each chromosome
Stage 3: Metaphase
- Spindle is fully formed
- Chromosomes align at spindle midpoint
* Moved by spindle microtubules
Stage 4: Anaphase
- Spindle separates sister chromatids and moves them to opposite spindle poles
- Chromosome segregation is complete
Stage 5: Telophase
- Chromosomes decondense
- Return to extended state typical of interphase
- New nuclear envelope forms around chromosomes
what is cytokinesis?
completes cell division by dividing the cytoplasm between daughter cells
