Unit 4.5-4.6 Cell Cycle (mitosis)

Mitosis is essential for…

repair and growth

Mitosis

Name given to cell division, where a cell divides into two genetically identical copies of itself, shortest stage of the cell cycle

Binary fission

type of cell divisions of prokaryotes (bacteria and archaea)

evolution of mitosis

probably evolved from binary fission, certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis

Types of stem cells

muscle cell, fat cell, bone cell, blood cell, nervous cell, epithelial cell, immune cell, sex cell

somatic cells

non-reproductive cells, have two sets of chromosomes

Gametes

reproductive cells: sperm and eggs, have half as many chromosomes as somatic cells

phases of the cell cycle

1. interphase

2. mitosis

3. cytokinesis

interphase

cell growth, DNA synthesis

which phase does a cell spend the most time at?

interphase

key features of interphase

nucleolus is visible, nuclear membrane surrounds the chromatin, individual chromosomes are difficult to see; not condensed into chromosome arms; =chromatin

G₁ phase

cell grows in size, organelles are duplicated, molecule building blocks necessary for cell division are produced, synthesizes proteins and organelles needed for cellular activities

ras

G₁ phase growth regulator protein, checks that cells are big enough to enter the next part of the cell cycle

p53

G₁ phase, inspect the chromosomes’ DNA for damage

s phase

centrosomes and DNA replicated, resulting in two identical sets of chromosome, each chromosome consists of two sister chromatids

G₂ phase

continues to grow and produce proteins needed for chromosome segregation

G₂ checkpoint

ensure that DNA has been fully and correctly replicated before the cell enters mitosis

ATM/ Nibrin

protein complex, inspects to make sure that DNA was copied without mistakes

DNA replication

cell must duplicate their DNA before mitossi so each new cell has an exact copy or the original

process of DNA replication

1. DNA unwinds and unzips, separating the bases

2. weak hydrogen bonds between nitrogenous bases break

3. new nucleotides pair with original DNA (A pairs with T, G pairs with C)

result of DNA replication

two idential DNA molecules each containing one old and one new strand

key of mitosis

genetic stability by ensuring each daughter cell has the same DNA

order of mitosis

prophase → prometaphase → metaphase → anaphase → telophase

prophase

1. DNA from replication coils up into sister chromatids which are joined in the middle by a centromere, forming the x shaped chromosomes

2. cylindrical organelles called centrioles organize spindle fibers to form the star shape called aster, which helps align and group chromosomes in cell division

3. the asters and centrioles (centrosomes) move to different poles

4. nucleolus disappears (late prophase/ early metaphase)

5. spindle fibers grow from centrosomes

centrosome

a section of the chromosome that the spindle fiber attaches to, comprised by two centrioles, crucial for microtubules organization and cell structure. They replicate to ensure each daughter cell receives a centrosome. They eventually move to opposite poles and form mitotic spindles

what are centrioles made of

microtubules

genome

the complete set of genetic material that contains instruction for development, growth and repair