Where Do Cells Come From?“All cells come from pre-

existing cells” -Cell Theory

3 types of cell divisions:

Mitosis-nuclear cell division in somatic cells, asexual reproduction

Meiosis-nuclear cell division in germ cells, sexual reproduction

Prokaryotic Fission-cell division in bacteria cells, asexual reproduction

Review of Terms used in Mitosis/Meiosis Somatic cells-all cells except

sex cells Germ cells-sex cells, sperm

and eggs Diploid-2 of every

chromosome Haploid-1 of each

chromosome Chromosome-a linear

arrangement of genes, composed of DNA

How many chromosomes are found in humans?

Which cells are diploid and haploid in humans?

Review of Terms used in Mitosis/Meiosis Chromatid-1 arm of

duplicated chromosome, sister chromatids

Centromere-area on chromosome that holds chromatids together

Histones-proteins associated with chromosomes, organize structure

Nucleosome-1 unit of DNA + 8 histones

Chromatin-all DNA + histones + other proteins

Eukaryotic Cell CycleInterphase-3 phasesG1-initial growth, G0 resting phase, permanently

arrestedS-synthesis, DNA is duplicatedG2-final preparations before mitosis, microtubule

formationMitosis-4 phases: Prophase, Metaphase, Anaphase,

TelophaseCytokinesis-division of cytoplasm

Most adult cells are in what phase of the cell cycle?

Control of the Cell Cycle Tightly regulated, require signals Cyclins required for cells to move

from G1S, G2M In mammalian cells p53 stops cycle

if DNA is damaged, hasn’t finished replicating, or if chromosomes are not attached to spindle

High levels result in apoptosis programmed cell death through caspases

MitosisProduces 2 identical diploid daughter cells

from 1 parent cellHave the same DNA clonesUsed for growth and repairAsexual reproduction used by some members

of fungi, plants, animals, protists

Mitosis-PMATProphaseChromosomes

condenseNucleolus

disappears, nuclear envelope breaks apart

Centrioles duplicate, move to opposite poles

Microtubules grab chromosomes in order to move them

Longest phase

Mitosis-PMATMetaphase-

microtubules align chromosomes at the equator of a cell, “metaphase plate”

Kinetochore spindle fibers attached to sister chromatids come from poles

Mitosis-PMATAnaphase-pulling apart

of chromatids/centromeres, microtubules contract, moving chromatids to opposite poles, “spindle apparatus” is clearly visible

Shortest phaseTelophase-chromosomes

decondense, nuclear envelope reforms, nucleolus reappears

Cytokinesis Division of cytoplasm Occurring

simultaneously with telophase

Occurs differently in plant and animal cells

Cell plate formation-Plant cells

Vesicles from golgi align at equator and fuse to form cell wall

Cleavage Furrowing-Animal Cells

Actin filaments align at equator (contratile ring)and contract until separate cell into two

Stem Cells and CloningStem cells adult cells that retain ability to divideCan differentiate into different types of cellsTherapeutic cloning produces human tissuesReproductive cloning new individual can be made

Cloning and Embryonic Stem CellsEmbryonic Stem Cells (ES)-cells from an early

embryo; these cells have not received the genetic instructions to become a specialized cell yet

These cells can be transferred into a organ and become that type of tissue. Example: ES cells defective pancreas, become pancreas cells and start producing insulin

Stem Cell Lines100s have already been created that are

heart, liver, pancreas, etc. cell linesEventually, transplant into humans; mice

studies are very promisingProblems: immune reaction Getting the cells to defective tissueEthical issues (no fertilized egg required)

Properties of Cancer Cells: loss of cell cycle control(When Compared to Normal Cells)

Additional chromosomes, genes

Grow and divide abnormally (faster)

Less adhesive, don’t stick to each other

Metastasize-migrate to other locations

Don’t communicate with each other

Don’t apoptose (die)

CancerUnregulated and

uncontrolled cellular growth

Form tumorsMetastasize

Cancer: Loss of Genetic Controls over Cells

Cell growth and repair is tightly regulated by genes; when these genes fail Cancer

Proto-oncogene (accelerator) normal growth gene becomes mutated oncogene, BRCA1

Tumor suppressor genes (brakes) -control cell death, ex. p53 gene

Causes of CancerUV, X-ray, gamma

radiation, chemicals in work places, smoking

Viruses Hepatitis C, liver cancer, HPV genital warts cervical cancer

Chromosome translocation leukemia

Carcinogens-cancer causing agents, ex. Compounds found in cigarettes

Cancer : Tumors and Treatment Benign-slow growth, no metastasis,

not lethal unless size becomes largeMalignant-rapid growth, metastasize,

destroy tissue around themTreatmentChemotherapy-targets quickly

dividing cells, both cancer and healthyRadiation Therapy-high energy

radiation targets only tumor

Prokaryotic Cell DivisionBinary fissionAsexual

reproductionNo nucleus, only

nucleoid regionSingle circular

chromosomeCell wall