meiosis
special 2-stage type of cell division in which 1 diploid (2n) parent cell produces haploid (n) cells (gamates)
- result: halving chromosome #
- sexually reproduction
- leads to production of gamates (sperm & eggs)
- daughter cells have half the amount of hereditary material as parent cell
Mei -> gamates
mitosis
process of nuclear division in which 2 daughter nuclei are genetically identical to the parent nucleus
- cytokinesis leads to 2 identical daughter cells
- lead to production of all other types of cells (somatic cells)
- cellular replication
mit -> somatic/other cells
phases of cell cycle
(1) M phase
(2) Interphase
interphase
portion of cell cycle btwn one M phase and the next
- DNA replication occurs here
- uncondensed chromatin
(1) G1 phase
(2) S phase
(3) G2 phase
*most cells spend their time here (not dividing stage - G1 phase)
M phase
2nd step of cell cycle
- cell division occurs here
- replicated chromosome condense
- sister chromatids separate
- 2 daughter cells formed by cytokinesis
division of nucleus & cytoplasm
M phase = PPMAT
G1 phase
1st step of interphase in cell cycle
- 4 unreplicated chromosomes
- non-dividing cells stuck here
- allow parent cell to grow large enough to divide into 2 cells that will fcn normally
growth phase
S phase
2nd step of interphase in cell cycle
- DNA synthesis (break down)
- chromosome replicated
“synthetic phase”
G2 phase
3rd step of interphase in cell cycle
- 4 unreplicated chromosomes
- sister chromatids
growth phase
gamate
haploid (n) reproductive cell
- can fuse w/ another haploid cell to form a zygote
(ie) eggs & sperm & precursor cells
gene
a section of DNA (RNA for some viruses)
- encodes info for building related polypeptides or fcnal RNA molecules along w/ regulatory sequences required for its transcription
deoxyribonucleic acid (DNA)
nucleic acid composed of deoxyribonucleotides
- double helix structure
- encodes cells’ hereditary info or genetic material
chromatid
1 of 2 identical double-stranded DNA composing a replicated chromosome
- sister chromatids connected @ centromere
number of chromosomes in human somatic cell
46 chromosomes
(23 chromosome pairs)
2n
cell cycle checkpoints
critical point in cell cycle in which cell progression is regulated
- G1 checkpoint
- G2 checkpoint
- M phase checkpoint
no pass checkpoint, cannot proceed onward
“is this ready?”
G2 checkpoint
(1) chromosomes must have replicated successfully
(2) no DNA damage
(3) MPF activated & present
G1 checkpoint
(1) adequate cell size
(2) sufficient supply of nutrients
(3) social signals present
(4) no DNA damage
M phase checkpoint
(1) chromosomes attached to spindles
(2) chromosomes properly segregated
(3) MPF absent
cytokinesis
cytoplasm divides to form 2 daughter cells
- occurs after M phase
cell divides
actin-myosin pinch plasma membrane
cytoskeleton roles during mitosis
(1) architectural framework cells can organize subcell organelles & metabolic machinery
(2) cell shape
(3) cell movement
(4) cell division
cyotoskeleton - cell shape
cytoskeleton determines cell shape (intermediate filaments)
cytoskelton - cell movement
microfilaments + microtubules assemble & dissemble to move cell
cytoskeleton - cell division
microtubules move chromosomes to daughter nucleus
kinase
enzyme that catalyzes transfer of phosphate group from ATP to a target protein
- subunit of MPF
- always present
cyclin-dependent kinase (Cdk)
protein related to kinase
- fcnal when bound to cyclin
- activated by other modifications
- regulates other proteins & cell cycle
benign tumor
mass of abnormal tissue due to unregulated growth
- does not spread to other organs
- not cancerous
could be caused by social control does not work properly
noninvasive
cancer
general term for any tumor whose cells grow in an uncontrolled fashion, invade nearby tissues, and spread to other sites in the body
malignant tumor
tumor that is actively growing & disrupting local tissues or spreading to other organs
invasive
metastasis
spread of cancerous cells from original site to distant sites in body
- may create additional tumors
social control over cell division
cells divide in response to signals from other cells
- social control of cell cycle based on growth factors
unreplicated chromosome
a single strand of double helix (DNA) wrapped around proteins
replicated chromosome
2 copies of double helices (DNA)
- same chromosomes
ploidy
number of copies of each chromosome
types of ploidy
(1) haploid
(2) diploid
haploid (n)
gamates
- one copy of DNA
diploid (2n)
somatic cells
- 2 copies of DNA
discovery of interphase
(1) subphases via autoradiography
(2) gap phases - pulse chase experiments
M phase components
(1) prophase
(2) prometaphase
(3) metaphse
(4) telophase
prophase
(1st stage of M phase)
chromosomes condense
spindle apparatus form
rearrange to reduce erros
“before phase”
prometaphase
(2nd stage of M phase)
nuclear envelope breaks down
microtubules contact chromosome @ kinetochore
rearrange to reduce errors
metapahse
(3rd stage of M phase)
chromosomes line up in the middle
rearrange to reduce errors
anaphase
(4th stage of M phase)
chromatids separate & pulled to opposite poles
accurately divide replicates
telopahse
(5th stage of M phase)
nuclear envelope reforms
chromosomes recondense
rearrange for normal fcn
binary fission
process of cell division
- similar to mitosis
- proteins different
- bacteria divide via fission
- used for asexual reproduction of many prokaryotic cells
creates 2 genetically identical cells
oncogenes
genes for proteins that causes cell to divide
“Go!”
tumor suppressor genes
genes that causes cell to stop dividing
“Stop!”
embryo
newly developing organism
histone
positively charged (basic) proteins associated w/ DNA in chromatin of eukaryotic cells
chromosome
single long DNA double helix wrapped around histones in a highly organized matter
- colored body
- threadlike structures
- made up of: DNA & genes
gene
a length of DNA that codes for a particular protein or ribonucleic acid (RNA) found in cell
sister chromatid
chromatid copies that remain attached @ their centromere
cell cycle
orderly sequence of events that lead to a eukaryotic cell through duplication of its chromosome to the time it divides
- made up of: M phase + interphase
timing depends on cell type & growth conditions
spindle apparatus
structure that provides mechanical forces
- consists of microtubules
function of spindle apparatus
(1) move replicated chromosomes during early mitosis
(2) pull chromatids apart in late mitosis
microtubule properties
(1) composed of alpha & beta tubulin dimers
(2) asymmetric structure
- plus & minus ends
plus end of mictrotubules
where growth occurs
minus end of microtubules
where disassembly occurs
cell plaste
flattened sac-like structure formed in middle of dividing plant cell
- originates from golgi-vesicles
- divides cytoplasm into 2 separate cells
cleavage furrow
pinching in of plasma membrane that occurs as cytokinesis begins
- deepens into cytoplasm until forms 2 daughter cells
- animals & otro eukaryotes only
oocyte
egg phase stuck in phase similar to G2 phase
- about to enter M phase
M phase promoting factor (MPF)
cyclin & Cdk complex that phosphorylates specific proteins needed to initiate mitosis
- found in eukaryotic cells
- MPF induces M phase
“start M phase please”
subunits of MPF
(1) kinase
(2) cyclin
cyclin
regulatory protein whose concentration fluctuates cyclically throughout cell cycle
- MPF subunit
how MPF is turned on?
(1) interphase - cyclin builds up
(2) Cdk regulated by two phosphorylation events
how MPF is turned off?
(1) anaphase - cyclin degradation [leads to destruction]
(2) negative feedback
(3) activated enzyme complex causes ubiquitin attaches to cyclin
types of tumors
(1) benign
(2) malignant
p53
tumor suppressor protein that responds to DNA damage
- stops cell cycle
- turns on DNA repair machinery
- (perhaps) triggers apoptosis or self-destruction
apoptosis
self-destruction
growth factors
a large number of signaling molecules
- secreted by certain cells
- stimulate other cells to grow, divide or differentiate
social control of cell cycle
serum
liquid portion of blood that remains after blood cells & cell fragments have been removed
components of serum
(1) water
(2) dissolved gases
(3) growth factors
(4) nutrients
(5) otro soluble substances
negative feedback
corrective response
change triggers responses aimed to return variable back to normal
- means of maintaining homeostais
- occurs when process is slowed or shut down by one of its products
E2F
transcription factor - initiates transcription
“Go!”