Cell Cycle, Mitosis, Meiosis

Binary fission (in prokaryotes)

The bacterial chromosome replicates; the two daughter chromosomes actively move apart

Binary fission step 4

Two daughter cells result.

G1 stage or Gap 1 stage

Typical daily life of a cell

Prometaphase

We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelope will fragment.

Chromatin

fairly unorganized DNA

Commonly occurring cancer is typically found in which cell types?

rapidly dividing cell types

Cell Division

the reproduction of cells

Chromosomes

tightly "coiled-coiled" DNA

Sister Chromatids

two identical chromosomes

cancer

unchecked cell division; cell division out of control; cancer is due to damaged DNA

Germ Cells

(a.k.a., Gametes; sperm & egg) -Meiosis

Aging & Cellular Clock Hypothesis

-Each time a somatic cell divides, a small portion of each chromosome is lost (telomeric region; a.k.a, telomere) -After many replications (10-50), a cell loses the ability to function normally. cell senescence --> apoptosis -There is an enzyme Telomerase, that "fixes" the telomeres but is only found active in germ cells and cancer cells

If you start with 2 chromosomes (2n=2), how many chromosomes do you have in each cell after meosis?

1

If you start with 2 chromosomes (2n=2), how many chromatids do you have after the S-stage?

4

benign tumor

A cluster of cancer cells localized (confined) to one region of the body

malignant tumor

A moving cluster of cancer cells through the blood stream

Down's syndrome

A.K.A Trisomy 21; dies to age 50; causes cardiovascular problems or respiratory problems

Patau syndrome

A.K.A. Trisomy 13; dies at age 1 or 2; causes mental impairments or cardiovascular problems

Edward's syndrome

A.K.A. Trisomy 18 or clenched fist syndrome; dies at age 7; only in females; causes muscle spasms, malformed skin conditions; visual impairments

Turners syndrome

A.K.A. XO; dies from 30-50 years of age; only in females; sex chromosomes do not disjunct properly

When do chromatids separate?

Anaphase 2

Binary Fission step 1

Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell.

Molecular checkpoints

Critical points during the cell cycle when the cell "divides" if everything is as it should be

S stage

DNA replication or DNA synthesis

Telophase

Daughter nuclei are forming. Meanwhile, cytoskeleton has started: The cell phase plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

Chromosomal Non-disjunction

During cell division, the chromosomes and tetrads do not always separate correctly and may result in daughter cells contain more or less chromosomes than they should!

Interphase is divided into what three stages?

G1, S, G2

Anaphase 1 of Meiosis 1

Homologous chromosomes separate

Supplemental Material for Interphase

In cell cycle, interphase is the period between two consecutive cell divisions, e.g. the interval between two mitoses (hence the name). Compared to mitosis, the interphase is generally longer in duration; it is comprised of three stages: G1, S phase, and G2. During interphase, the cell typically undergoes growth (i.e. increases in cell size) and makes a copy of the cell's DNA to prepare for the next cell division.

*Most of a cell's life is spend in what phase?

Interphase

Anaphase 2 of Meiosis 2

Sister chromatids seperate

Binary fission step 2

Replication continues. One copy of the origin is now at each end of the cell.

Binary fission step 3

Replication finishes. The plasma membrane grows inward, and new cell wall is deposited.

G2 stage or Gap 2 stage

Replication of organelles and various cell division machinery

Functions of Cell Division

Reproduction, Growth, Development, Tissue Renewal

Restriction point

Right before S-phase, when the cell "decides" to stay exactly like it is

When does DNA synthesis occur?

S Stage

DNA synthesis occurs in what stage?

S stage of Interphase

Anaphase

The chromatids of each chromosomes are moving to the ends of their cell as their kinetochore microtubules shorten.

Prophase

The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is starting to form.

mitosis vs meiosis

The function of mitosis is to produce diploid cells such as somatic cells. The function of Meiosis is to produce haploid cells such as gametes. Tetrad formed in Prophase 1 of Meiosis 1. Tetrads line up in Metaphase 1 of Meiosis 1. Homologous chromosomes separate in Anaphase 1 of Meiosis 1. ////////////////////////////////////////////////////////////////////////// *Both have DNA replication. Number of division in mitosis is one Number of division in meiosis is 2. Synapsis (the moving of homologous pairs together) occurs only in meiosis, not mitosis. Mitosis produces two daughter cells. Meiosis produces four daughter cells. Chromosome Numbers for mitosis is 2N. Chromosome Numbers for meiosis is 1N. All (human) daughter cells have 46 human chromosomes from the (human) parent cell that has 46 human chromosomes for mitosis. All (human) daughter cells have 23 human chromosomes from the (human) parent cell that has 46 human chromosomes for meiosis. Also, haploid cells can go through mitosis...1N makes more 1N cells. Also, 2N, 4N, 6N, 8N, etc cells can go through mitosis or meiosis depending if the cell is a somatic or germ cell.

Define Interphase

The phase in the life cycle of a cell wherein the cell is not undergoing cell division (as compared to mitosis and meiosis)

Metaphase

The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate.

syngamy

Three sexual life cycles differing in the timing of meiosis and fertilization; (see diagram in power points and be able to draw it)

*The sequential events of the cell cycle

are directed by a distinct cell cycle control system, which is similar to a clock.

Centromere

central binding location for sister chromatids

Genome

consists of all your DNA

cytokinesis

division of the cytoplasm; can begin in Telophase in animal or plant cells; involves formation of a contractile ring of actin and myosin molecules in animal cells

karyokinesis

division of the nucleus

Somatic Cell

every cell in your body but the sex cells -Mitosis

cell plate

formation of a cell plate results from cytokinesis in plant cells when vesicles merge; (A disc like structure in the plane of the equator of the spindle that separates the two sets of chromosomes during cytokinesis; also involved in the formation of cell wall between the two daughter cells following cell division)

cleavage furrow

formation of a cleavage furrow results from cytokinesis in animal cells; (A groove formed from the cell membrane in a dividing cell as the contractile ring tightens)

Haploid

having one copy of every gene (our sperm & egg); having one gene for every trait

Diploid

having two copies of every gene (our somatic cells); having two genes for every trait

Watch this video.

http://www.youtube.com/watch?v=bRcjB11hDCU

When do tetrads align along the middle of the cell?

metaphase 1

What can slow/stop cell division?

molecular checkpoints, restriction point, crowding

Crossing over

occurs in Meiosis 1; (A process occurring during meiosis wherein two chromosomes pair up and exchange segments of their genetic material)

Independent Assortment

occurs in Meiosis 1; The results of alternative arrangements of two homologous chromosome pairs on the metaphase plate in meiosis 1