Cell Division

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Cell division

Cell division

Process in which a parent cell divides into 2+ daughter cells

Parent cell

The cell that’s dividing

Daughter cell

A cell resulting from division

Mitosis

Needed for growth & repair

Meiosis

Needed for reproduction

Chromatin

How DNA is organized for most of a cell’s life– loosely wrapped around proteins

Histone protein

Protein that chromatin wraps around

Chromosome

How DNA is organized during division– one long strand of condensed DNA forming an X-like shape

Interphase

Cell carries out normal functions, aqcuires nutrients, and prepares for division

G1 phase

Part 1 of interphase– all organelles duplicate, cell grows

S phase

Part 2 of interphase– DNA copied, makes sister chromatids

Sister chromatid

Half a chromosome

G2 phase

Part 3 of interphase– cell grows more, enzymes for division made

Why cell growth?

So the daughter cells can be the right size

Why copy the DNA?

So each daughter cell has enough

M-phase

Active cell division– subdivided into mitosis and cytokinesis

Somatic

Relating to body cells (skin, muscles, etc.)

Centriole

Makes spindle fibers

Spindle fiber

Protein ropes that attach to chromosomes to move them around the cell

Centromere

Where two sister chromatids meet

Daughter chromosome

When sister chromatids separate

Apoptosis

Programmed cell death (when something irreparable is wrong with a cell)

Cancer

Disease of uncontrolled cell division, result of accumulated mutations in the genes that control cell division

Proto-oncogene

Produces proteins that decrease cell division (“stop” signal)

Tumor-suppressor gene

Produces proteins that increase cell division (“go” signal)

Self-sufficiency in growth signals

Growth factors are required for normal cells for division and growth, but cancer cells can divide with or without them

Growth factor

Molecules (usually hormones) that signal when it’s time for a cell to grow

Insensitivity to anti-growth signals

Normal cells have processes to control cell growth & division and stop when the space they inhabit is filled– cancer cells don’t because of mutations

Evading apoptosis

Cancer cells mutate to be unable to trigger apoptosis signal

Limitless reproductive potential

Normal cells have a limited # of times they can divide because of telomeres, cancer cells increase telomere length meaning they can divide an infinite number of times

Telomere

Thingies at the end of chromosomes that shorten to control the # of times a cell can divide

Sustained angiogenesis

Cancer cells steal nutrients from blood vessels, weakening other cells and increasing tumor growth

Angiogenesis

Growth & development of new blood vessels

Tissue evasion and metastasis

Cancer cells invade tissue cells, enter blood stream, then invade tissue cells elsewhere, spreading throughout the body

Metastisize

Ability to spread to tissues throughout the body

Malignant cancer cells

Cancer cells able to spread throughout the body

Diploid cell

Contains 2 copies of each chromosome

Haploid cell

Contains 1 copy of each chromosome

Homologous chromosomes

2 chromosomes of same size, same genes in same order– exist in pairs, one maternal one paternal

Meiosis

Process of division that ends with 4 genetically unique haploid gametes

Gamete

reproductive cell like sperm and eggs

Zygote

1st cell of an organism

Why genetic variation?

Less chance for mutations to pass on to daughter cells

Prophase

Step 2

–DNA condenses, forming chromosomes

–nucleus unforms

–centrioles form

Metaphase

STep 3

–Spindle fibers attach to centromeres

–Align chromosomes in the middle

Anaphase

Step 4

–Spindle fibers shorten, centromere splits

–sister chromatids pulled apart to opposite ends of the cell

Telophase

Step 5

–chromosomes reach spindle poles

–nucleus reforms

–chromosomes turn back into chromatin

–spindle fibers disintegrate

Cytokinesis

Step 6

–Cell splits into 2 identical daughter cells

–Animal cells– cytoplasm splits

–Plant cell– new cell wall forms down the middle

Prophase 1

Step 2

–Homologous chromosomes pair up

–Crossing over– DNA exchanged

–Otherwise same as in mitosis

Metaphase 1

Step 3

–Homologous chromosome pairs line up down the middle

Anaphase 1

Step 4

–Spindle fibers pull apart homologous chromosomes

Telophase 1/Cytokinesis

Step 5

–Cytoplasm divides– 2 haploid cells w/ 2 copies of each gene

–Sister chromatids have 2 copies of each gene

Prophase 2

Step 6

–Same as prophase 1, but no crossing over

Metaphase 2

Step 7

–Single chromosomes line up down the middle of the cell

Anaphase 2

Step 8

–Spindle fibers pull apart sister chromatids

Telophase 2/Cytokinesis

Steps 9 & 10

–Telophase same as the last one

–4 haploid cells total with 1/2 the DNA of the original chromosomes

–1 copy of each gene

Stem cells

Cells from which all other cells with specialized functions are created

Differences between spermatogenesis and oogenesis

–Polar bodies created in oogenesis and die

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Gametogenesis

Gamete production

Differentiation

Process under which a cell matures into having a more specialized function (by turning on and off different genes)