Bio H - U10 Cell Growth

Rudolf Virchow

Concluded that all cells come from other cells

Reason why cells are needed

growth, repair, reproduction

Cell cycle

regular pattern of growth, DNA duplication, and cell division in eukaryotic cells. 2 main stages: interphase and mitosis

Interphase

longest phase of cell cycle. Cell grows, DNA and organelles are replicated/copied and additional growth. Steps of interphase: G1, S, G2

Gap 1 (G1)

carries out normal functions (MAKING PROTEINS)

Synthesis (S)

DNA replication

Gap 2 (G2)

Prepare organelles to duplicate and prep for mitosis (division of cells)

Mitosis (M Phase)

create two genetically IDENTICAL daughter cells with the SAME # of chromosomes as parent cells. Both have SAME FUNCTION

Chromosome

tightly condensed DNA and protein structure (X shape when duplicated)

histones

the protein DNA coils around

nucleosome

segment of DNA wrapped around 8 histones

coil/supercoil

increasingly more complex tightly-packed DNA

chromatin

loosely packed mass of DNA and proteins (NOODLE SOUP; default structure of DNA)

Chromatid

half of a duplicated chromosome

sister chromatids

two halves of a duplicated chromosome (created in S phase)

centromere

location where sister chromatids are joined

telomere

end caps of chromosome (PROTECTIVE CAPS that have NO genetic code)

Prophase

• chromatin condenses to chromosomes

• centrioles → opposite ends of cell

spindle fibers

thin tubes part of cytoskeleton that pull chromosomes apart

Metaphase

• chromosomes align in Middle

• spindle fibers attach to centromere

Anaphase

• sister chromatids (duplicated chromosomes) → chromatids

• chromatids pulled to opposite ends

Telophase

• spindle fibers disappear

• nuclear membrane reforms around each daughter cell

• chromatids → chromatin (NOODLES)

• nucleus divides (overlaps with cytokinesis)

Cytokinesis

division of cytoplasm

Cytokinesis in animals

cleavage furrow (indented part) pinches cell membrane out

cytokinesis in plants

cell plate forms in middle of cytoplasm and grows into cell membrane (from in → out)

G0 Phase

No growth phase; cell leave cell cycle and don’t divide (e.g. brain tissue)

Cell cycle checkpoints

happens 3x, ensure stages happen correctly and cell isn’t damaged. If damaged, APOPTOSIS. Regulates cell growth

Apoptosis

programmed cell death

1st checkpoint

After G1. Checks DNA for damage before copying

2nd checkpoint

after G2. checks if parts of cytoskeleton are in tact for division

3rd checkpoint

middle of mitosis. Checks if two copies of DNA are attacked to spindle fibers (cytoskeleton)

Growth factors

broad group of proteins that stimulate cell division

cancer

uncontrolled cell division due to a break down in the regulation of the cell cycle

Normal cells

• density-dependent (crowded cells stop dividing)

• anchorage-dependent (must be attached to surface to divide)

• Normal angiogenesis (BLOOD VESSEL GROWTH)

Cancer cells

• density-INDEPENDENT

• anchorage-INDEPENDENT

• Advanced angiogenesis (AGGRESSIVE blood vessel growth)

benign tumor

doesn’t invade nearby tissue/spread to rest of body

malignant tumor

harmful tumor that can metastasize

metastasize

when tumor cells invade bloodstream, break away and travel to other parts of the body

carcinogens

cancer causing agents, result in mutations in DNA

oncogenes

genes responsible for normal cell growth (cancerous→when mutated and permanently turned in)

tumor suppressor gene

prevent unrolled cell growth by repairing damaged DNA

cyclins

proteins that control the timing of the cell cycle (rise and fall at regular intervals)

asexual reproduction

production of genetically identical offspring from a single parent (binary fission, budding, fragmentation)

advantages of sexual reproduction

genetic diversity and better suited to survive

disadvantages of sexual reproduction

• slower and need more energy

• need a mate

advantages of asexual reproduction

• fast

• no mate needed

• well adapted (in environment stays the same)

disadvantages of asexual reproduction

no genetic diversity/variation

Somatic cells

SPECIALIZED body cells. NOT passed to offspring and created through mitosis. diploid

Gametes

sex cells. PASSED to offspring and created thru meiosis. haploid

diploid

cells that have a full set of chromosomes (46 in humans, abbrev. 2n)

haploid

cells that have HALF the diploid number of chromosomes (23 in humans, abbrev. '“n”)

sexual reproduction

union of sperm and egg to make diploid cell via fertilization

fertilization

union of sperm and egg (one diploid from two haploids)

homologous chromosomes

a pair of the same chromosomes, one paternal and one maternal (same size and genes)

autosomes

chromosome pairs 1-22 (typically do not have human’s sex and carry most genes)

sex chromosomes

chromosome pair 23 (determines sex; females - HOMOLOGOUS XX and Males NON-homologous XY)

Karyotype

display of someone’s chromosomes to determine sex of person and chromosomal disorders (chromosomes paired and sorted acc to size)

nondisjunction

when HOMOLOGOUS chromosomes or sister chromatids fail to separate (occurs in meiosis I or II) CAUSES ANEUPLOIDY

aneuploidy

cell with abnormal # of chromosomes

meiosis (general)

process where sperm and egg cells are created by cutting the # of chromosomes in HALF (so each cell in unique)

tetrad

pair of homologous chromosomes with 4 chromatids

crossing-over

exchange of genes between homologous chromosome. Now has mixture of parental genes!

Meiosis I

Prophase I, Metaphase I, Anaphase I, Telophase I / Cytokinesis I.

Separates HOMOLOGOUS CHROMOSOMES to make 2 HAPLOID CELLS

Meiosis II

Prophase II, Metaphase II, Anaphase II, Telophase II / Cytokinesis II.

Separates 2 HAPLOID to FOUR HAPLOID

Prophase I

replicated chromosomes pair with homologous to form tetrad. tetrads cross over

Metaphase I

homologous pairs line up in Middle and spindle fibers attach. Tetrads ASSORT INDEPENDENTLY

independent assortment

the random alighnment of homologous pairs during Metaphase I. Increases genetic diversity

Anaphase I

Homologous chromosomes → opp sides of cell. Siser chromatids ATTACHED STILL (diploid still)

Telophase I / Cytokinesis I

Nuclous briefly forms. 2 genetically-unique HAPLOID CELLS!

Prophase II

nucleus breaks down

Metaphase II

sister chromatids line up in middle

Anaphase II

SISTER CHROMATIDS separate

Telophase II / Cytokinesis II

Nucleus reforms. Creates 4 genetically UNIQUE HAPLOID cells