GenBio Mitosis Quiz

Organisms grow & maintain & reproduce

happen due to cell division → only small part of cell's life

Cell cycle

3 stages: Interphase (preparatory stage For cell division). M Phase (either mitosis or melasic) -> only For eukaryotes. Cytokinesis (Cyto-cytoplasm / body. Kinesis-division, division of Cytoplasm)

Binary Fission For prokaryotes - simpler & Faster than mitosis &

melosis

Interphase

lists down / prepares the things that need to be duplicated (organelles & the content needed to give both cells DNA)

the cell doesn't divide, only grows

majority (90%) of cell's life (10%, cytokinesis & M phase) - 12-24 hrs in mammals

nuclear membrane & nucleolus are very distinct (larger)

To Do List: Growth, DNA Replication

-G (represents growth; G0 G1 S G2)

G0 (Gap 0 Phase)

not counted For Interphase bcs the cell doesn't prepare during this, only rests.

present for nervous system cells (esp brain cells) so they stop dividing

can happen bcs of nutrient deficiency (IE malnourishment) or as cells reach their max lifespan

G1 (Gap 1 Phase)

centrosome (essential for cell division) gets ready to double

cell grows

only 1 chromatin thread during this

S (Synthesis phase)

centrosome doubles

Chromatin doubles → 2 chromatin thread

goal is to replicate DNA in the Form Of Chromatids

G2 (Gap 2 Phase)

duplicates the things that didn't duplicate during G1

double checks content & looks for errors

prevents cell division if something is amiss

occurs b4 the prophase

Telomere

not coding DNA (won't make proteins

Important in securing genetic material to prevent accidents

damage to this may lead to mutations

decrease in size every cell division & that's why cells stop dividing & enter Gap 0 to try & restore these

Chromatids

still considered a chromosome

half of a “whole” chromosome

Humans have 92 chromatids (2 sets of 46 chromosomes) but more # of chromosomes ≠ more complex organisms

Sister Chromatids

called this bcs they're connected

centromere

attaches chromatids & also sister chromatids

# OF centromeres = # of chromosomes

ex: 1 chromatid & 1 sister chromatid Pair = 2 chromosomes, 2 chromatids & 3 sister chromatid pair = 5 chromosomes

Kinetochore

on the centrosome

where spindle Fibers attach during cell division to pull sister chromatids apart

Cell Division

cell process that uses division to multiply

development of how cells (daughter cells) Form From pre-existing cells (parent cells)

Prokaryotes (bacteria)

undergo a vegetative cell division known as Binary Fission (genetic material segregated equally into 2 doughter cells)

only processes are DNA replication & cytokinesis

sometimes the DNA is shorter than eukaryotes so the division is faster

parent cell - DNA dupes → cytoplasm divides → daughter Cells

Eukaryotes

mitosis & meiosis

Mitosis

between somatic cells (body cells)

one single division of parent cells → 2 daughter cells

each daughter cell is genetically identical to the parent cell

(both parent daughter cells are diploid cells)

2n; n=23 → complete set of chromosomes.

no genetic diversity to prevent errors in body cells / mutation risk

# OF Chromosomes per nucleus remains the same

genotype of parent daughter cells remains the same each daughter cell has the same DNA strands

no pairing of homologous chromosomes

no DNA exchange (crossing-over) between chromosomes

goals: growth & repair

Stages of Division (PMAT)

 M Phase

4th & Final phase of cell cycle

mitosis (only nucleus Fully divides) and cytokinesis (cytoplasm Finishes dividing)

somatic cells

diploid # (2n) or complete set of chromosomes

pairs of homologous chromosomes (unike gametes which have non-homologous chromosomes)

Prophase

Chromatin (long DNA threads, not yet in the form or chromosomes) are coiled into chromosomes w/ each chromosome having 2 chromatids joined at a centrosome

mitotic spindle (made of microtubules & proteins) Form in the cytoplasm & go to opposite sides of the cell

need to turn chromatin (uncoiled Form is mainly in Interphase) → chromosomes bcs it's easier to divide them into 2

mitotic spindle Fibers (centrioles & asters → at the poles) are formed

breakdown of nuclear membrane /envelope to let out chromosomes

longest mitosis phase

Metaphase

nuclear membrane completely disappears

chromosomes align at the cell's equatorial plane (middle)

important so there's even pressure when pulling chromosomes so they split into an even # of chromatids so that a whole chromosome doesn't get pulled to one side of the cell

Anaphase

daughter chromosomes (chromatids that have separated) move to poles at opposite ends of the cell

start of cytokinesis (lasts until after Telophase since bcs cytoplasmic division is slow)

Telophase

chromosomes have reached opposite poles

nuclear membrane starts to reform & the nucleus and nucleolus start to appear

chromosomes start to elongate & unwind

bcs of cytokinesis, a cleavage Furrow (animal) or cell plate (plant) is formed here to divide the daughter cells

Cytokinesis

complete division of cytoplasm which occors after mitosis

starts anaphase, ends after telophase

Karyokinesis

division of nucleus

starts at prophase, ends at telophase

Milosis Significance

Cell Replacement

Growth

Regeneration

Cell Replacement

cells are constantly sloughed OFF, dying, and are being replaced by new ones in the skin & digestive tract

Growth

mitosis is the basis of growth in multicellular organisms bcs # OF cells in the organism increases

Regeneration

Some animals produce body parts using mitosis to produce new cells

Cell cycle control

checkpoints

3 in mitosis (G2 checkpoint, Metaphase checkpoint, G1 checkpoint)

"check point genes" → may cause mutations iF Faulty

Cell cycle control ex

p53 protein - operates at the end of G1; Causes apoptosis (cell death if damage can't be repaired); may cause tumors/cancer iF mutated

G2 checkpoint

checks cell size and DNA replication

Metaphase checkpoint

checks chromosome spindle attachment

G1 checkpoint

Checks nutrients, growth factors, DNA

Tumor

some mutations affect Function of check point genes

cell divides when it shouldn't → mass of abnormally dividing cells in a tissue

benign and malignant

Benign tumor

stays in place

Malignant tumor

cancer; moves out from home tissue → metastasis

Oncogenes

mutated or over-expressed proto-oncogenes that cause unregulated cell division

proto-oncogenes

regulate cell division

Meiosis

between gamete cells.

unidentical daughter cells

no. OF Chromosomes in daughter cells is reduced by half to produce haploid gamete daughter cells (1n; half of a set of chromosomes)