human cell
46 chromosomes (23 pairs)
reason for cell division
allows a unicellular organism to reproduce an entire organism (increases population), repairs dead/damaged cells, allows multicellular organisms to grow, important for the development of a multicellular organism that begins as one cell, increases rate of
asexual reproduction
the creation of genetically modified offspring by a single parent, without the participation of a sperm and egg; many multicellular organisms can reproduce asexually as well
sexual reproduction
requires the fertilization of an egg by a sperm; a gamete (sperm/egg) only has half as many chromosomes as the parent cell; offspring are not identical to their parents, but resemble them more than other random individuals; cell division enables sexually
binary fission
dividing in half; duplication of chromosomes, separation of the copies, continued elongation of the cell and movement of the copies, division into two daughter cells; how prokaryotes reproduce
genome
a cell's genetic information, packaged as DNA
chromosomes
a spool of DNA strands
gametes
sperm or eggs (3 chromosomes per cell), this is the only DNA that differs between humans
proteins
DNA wraps around these to condense
sister chromatids
identical copies of a chromosome's DNA, connected together by proteins to form an X shape
centromere
connects two sister chromatids in the narrow area of the X shape
cell cycle
interphase, prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis
G1 (first gap)
centers on growth; produces organelles
S (synthesis)
when the chromosomes are copied; longest phase
G2 (second gap)
where the cell completes preparations for cell division; shortest phase
interphase
cell synthesizes new molecules and organelles; chromosomes duplicated but still in the form of loosely packed chromatin; 90% of the cell cycle
interphase
mitosis phases
prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis
mitosis
the process of the formation of two daughter nuclei which are genetically identical to the parent; much shorter than interphase; unique to eukaryotes as it solves the problem of allocating an identical copy of the whole set of chromosomes to each of the t
spindle
microtubules made of protein, stemming from each pole of the cell; job is to organize the chromosomes, then split them in half; performs the movement required in cell division
kinetochore
location at the centromere of chromosomes where the spindle attaches (analogy: hook)
prophase
longest phase of mitosis; chromosomes are more tightly coiled, forming discrete chromosomes with sister chromatids joined together; nucleoli disappear (nuclear membrane starts to break down), mitotic spindle begins to form and appears to push the centroso
prophase
prometaphase
microtubules attach to their respective kinetochores, nuclear membrane is fully broken down, centrosomes have moved to poles of the cell; chromosomes begin to move to the center of the cell
prometaphase
metaphase
spindle fibers push the sister chromatids until they are all arranged at the metaphase plate; mitotic spindle fully formed; spindles attached to kinetochores of each chromosome
metaphase plate
an imaginary plane equidistant between the poles; where chromatids line up during metaphase
metaphase
anaphase
begins when centromeres divide, separating the sister chromatids; pulling kinetochore as spindle fibers start to break down; by the end, the poles have equivalent collections of chromosomes
anaphase
telophase
shortest phase of mitosis; cell continues to elongate as free spindle fibers from each centrosome push off each other; two nuclei begin to form, surrounded by the fragments of the parent's nuclear envelope; chromatin becomes less tightly coiled; like the
telophase
cytokinesis
division of the cytoplasm that follows mitosis; usually occurs simultaneously with telophase
cleavage furrow
first sign of cytokinesis in animals; a shallow groove in the cell surface near the old metaphase plate; result of actin/myosin ring contracting
cell plate
first sign of cytokinesis for plants: a membraneous disk that is not as defined or thick as a cell wall; grows outward, accumulating more cell wall materials as more vesicles fuse with it; eventually becomes a cell wall that divides the two daughter cells
cancer
an uncontrolled growth of cells, a genetic disease, and a family of similar disease, healthy cells turn into the enemy as they divide too quickly/abnormally, become abnormal shapes and sizes, and grow in all directions; cells stop listening to the body, w
tumor-suppressor (TS) genes
BRAKE, normally inhibit cell growth ("checks" during the cell cycle); recessive, so both must be mutated to mess up the cell cycle; e.g. BRCA 1/2 and p53
TS gene mutations
BRAKE BREAKS, mutations inactivate them, so they cannot stop cell growth (no more "checks" in the cycle, so bad cells will keep dividing)
proto-oncogenes
CAREFUL GAS, carefully promote cell growth; dominant, so only one needs to be mutated to mess up the cell cycle; e.g. RAS
oncogene mutations
FULL GAS, over-activates them, so they always promote cell growth; leads to cancer
benign
a non-malignant tumor that lacks the ability to invade surrounding normal tissue
malignant
a tumor that tends to grow, has the capacity to invade nearby tissue and spreads through the bloodstream
angiogenesis
creating new blood supplies for cancer to be able to spread (cancer sends proteins to nearby blood supplies)
metastasis
cancer cells spreading to the other parts of the body (developing secondary malignant growths)
local tumor treatments
radiation (shoot proton or electron beams at a certain area and the radiation so badly damages the DNA inside a cell nucleus that the cells can't divide anymore, so they die), surgery (excise it)
treatment
drugs (chemotherapy)
apoptosis
cell death
kinase
enzymes that add a phosphate to other proteins to activate or inhibit their function
cyclin
oncogenes that are the most important cell checkpoints; when activated, they act as an activating protein and bind CDKs to form a cyclin-CDK complex
G(0)
resting/nondividing stage; cells here may not have enough resources to divide, may not need to divide (neurons), and may depend on the organism's stage of development to continue mitosis