Biology -- Chapter 17

Front 1

What is mitosis?

Back 1

Eukaryotic cell division. Similar to bacteria division, but more complex. Thus it is also heavily regulated to prevent unchecked growth.

Front 2

At what point are they committed to replicating?

Back 2

S phase.

Front 3

Chromosomes?

Back 3

Condensed chromatin . Paired as sister chromatids. Chromatids are joined at centromere.

Front 4

Chromatin?

Back 4

DNA and protein strands.

Front 5

Homologous chromosomes?

Back 5

Two pairs of sister chromatids that are chromosome pairs of the same length, centromere position, and staining pattern, with genes for the same characteristics at corresponding loci.
Each parents donates one of the HC. There is also a domination effect, since there can be different alleles (one for blue eyes, and one for dark.. the dark one will dominate).

**Paired sister chromatids only exist in cells undergoing cell division.

Front 6

First stages of mitotic cell division in an animal cell?

Back 6

(1) G2 of interphase -- centrosomes with centriole pairs. Chromatic is duplicated.
(2) Prophase -- centrosomes move apart with early mitotic spindles inbetween the centrosomes. Asters (cellular structure that is star shaped) surround each of the centrosomes. Sister chromatids (condensed chromatin) join together at a region called the centrosome mer-port. Also, nucleolus disperses (no longer needed to make ribosomes).

**Also, in prophase there are chromosomes.

Front 7

Each centrosome contains?

Back 7

a pair of centrioles (in animals). each centriole has 9 microtubule triplets.

Front 8

a centrosome is a:

Back 8

MTOC (microtubule organzing centre). Plants have MTOCs too, but they lack centrioles.

Front 9

Prometaphase?

Back 9

Third step: chromosomes are fully condensed and jinectochore proteins attach on to each sister chromatid @ the centromere.
Also, kinectochores attract MTs that bind to the kinectochore proteins. Once attached, they are called kinectochore MTs.
- Nuclear envelope fragments.

Front 10

non-kinectochore MTs?

Back 10

Will attach to another non kinecto MT from the other centrosome. As MTs grow from the MTOC, it pushes the centrosomes apart.

Front 11

What exactly is a kinectochore?

Back 11

The kinectochore are specialized protein plaques aligned in the centromere of the centrosome during mitosis. Branching out from them are the kinectochore MTs.

Front 12

Later stages of mitosis in animal cells?

Back 12

(4) Metaphase: Kinectochore MTs orient the chromosomes through the equator of the cell -- called the metaphase plate region. Not a physical plate. **Check point for mitosis. All kinectochores (for each sister chromatid - 2 per chromosome) must be bound by kinectocre MTs before cell proceeds to next phase.

(5) Anaphase: Glue holding sister chromatids together breaks, leaving 2 daughter chromsomes each still attrached to their own kinectochore MTs down which molecular motors will carry them. -- Includes continuing lengthening of non-kinecto MTs and further elongation of the cell.

Front 13

Last stages?

Back 13

(6) Telophase and cytokinesis: Actin microfilaments and myosin motors act like belts on inner surfaces of plasma membranes to pull membranes together until it fuses and two daughter cells are created. While this happens, fragments of the nuclear envelope (happened in prometaphase) are used to make a new nuclear envelope.

Front 14

Cleavage furrow?

Back 14

The space in between the two emerging daughter cells.

Front 15

Difference between cytokinesis in animals and plant cells?

Back 15

Animals: Cleave furrows, and the cell gradually turns into two
Plants: Cell plate forms in between two new genetic materials, then the cell just splits, each having a new cell wall on the common side.

Front 16

Two exceptions to the nuclear envelope fragmenting?

Back 16

Dinoflagellates (protists) -- nuclear envelope stays intact. Chromosomes attach to membrane, microtubules pass through channels, and the whole nucleus divides.

Diatoms (protist) -- Spindle forms within the intact nucleus.
Nucleus divides.

**Remember though that these are rare exceptions.. most plant and animals cells have the nuclear envelope fragment.

Front 17

g1 and g2 checkpoints?

Back 17

G1: controls if the cell divides or not. Most of our cells are non-dividing, so they stop here (said to be in a state of G0 non-growth).

G2: checks whether cell is ready to divide or not.

Front 18

Growth factors?

Back 18

external signals to start dividing. Can (1) signals cells in G0 to start dividing, and (2) maintain cell division (often used in cell cultures).

e.g., EPO -- banned at Olympics. stimulates red blood cell production.

Front 19

Difference between normal mammalian cells and cancerous cells?

Back 19

Mammalian cells are (1) anchorage dependent, in that they need to be anchored to something to start dividing. They also have a (2) density-dependent growth rate, in that once they have formed a dense layer, they stop dividing. If some are scraped away, they'll start again, but stop once complete.

Cancerous cells do NOT have either of these properties, which is why they can grow so out of control.

Front 20

Transformed cells?

Back 20

Mutation of genes. defects are passed on. Most are killed by immune system. All it takes is one to live on though, and you have tumours starting.

Front 21

Three types of tumours/cancers?

Back 21

(1)Benign-- Localized, slow growth -- easily treated

(2) Malignant -- invasive, may change forms and chromozomes. CANCER!

(3) Metastatic cancer -- breakaway cells get into circulation and other tissues. Worst prognosis.

Front 22

What's one way to prevent cells from dividing without destroying those that are normally dividing?

Back 22

As tumours grow they
need their own blood
supply
new veins & arteries

Prevent this from
occurring