Stem Cells and Cancer

Development of an Organism

Gene Expression

1) Cells--> Tissues--> Organs--> Organ Systems

  • Fertilized egg= zygote

2) Zygote--> organism involves three processes

  • Cell division: cells divide indefinitely into more genetically identical cells 
  • Cell differentiation: cells become specialized in structure and function
    • specific activators in the cell turn on a collection of genes that determine what type of cell will result from differentiation 
  • Morphogenesis: cells distribute into a 3-D format

3) Three inductive signals that are important during embryonic development

  • A. Specific genes expressed at specific times determine how the organism develops
  • B. Cytoplasm of the egg: contains RNA and DNA
    • contains cytoplasmic determinants: maternal substances in the egg that influence the course of early development
  • C. Signals from the environment around a cell can cause changes in target cells (cells that are affected by certain agents)

 

Differentiation of Cell Types

  1. Tissue specific proteins: found only in a specific cell type and give the cell its characteristic structure and function
  2. 1st evidence of differentiation: appearance of mRNAs for tissue specific proteins
  3. Myoblasts: embryonic cell that becomes a cell of muscle fiber

Apoptosis

  1. Apoptosis: type of programmed cell death
  2. How does it occur? 
    • Cellular agents cut up the cell's DNA that died
    • The cell parts are packaged up in vessels (blebbing)
    • The blebs are engulfed by scavenger cells

Pattern Formation

  1. Pattern formation: setting up the body plan in which tissues and organs are all in their characterized places
    1. positional information: molecular cues that control pattern formation

Cloning and Stem Cells

Cloning Organisms

  1. Cloning: development of an organisms from a signle cell without fertilization and meiosis
    • Organismal cloning: one or more organisms produced is genetically identical to the parent that donated the single cell
      • Has a potential to generate stem cells
  2. Cloning plants and animals
    1. Plants
      1. totipotent: cell with the potential to dedifferentiate and give rise to various specialized cells
    2. Animals
      1. nuclear transplantation: remove nucleus of an egg and replace it with a nucleus of a differentiated cell
      2. Reproductive cloning: producing a genetically identical duplicate of an existing organism
        1. Dolly: a lamb that was cloned through nuclear transplantation from the egg of an adult sheep

Faulty Gene Regulation:

  1. Cloned animals that appear normal do have subtle defects and may be slightly different from each other
  2. DNA in cloned organisms may have extra methyl groups that interfere with gene regulation

Stem Cells

  1. Stem Cell: cell that can both reproduce itself indefinitely and differentiate into many specialized cells
  2. Blastula stage: when stem cells are isolated from early embryos
  3. Embryonic Stem cells: reproduce indefinitely and are the most versatile stem cels because they can differentiate into several specialized cells
    • Can be used to treat diseases through therapeutic cloning
  4. Adult stem cells: can replace non-reproducing specialized cells, but are hard to locate in the body
  5.  Induced Plutipotent Stem cells (iPS)- transformed differentiated cells into stem cells
    • Can be used to replace patients' nonfunctional tissues

Cancer Development

Genes Associated With Cancer

  1. Alteration in genes involved with the cell cycle in somatic cells can lead to cancer
  2. Oncogenes- genes that cause cancer
  3. Proto-oncogenes- normal versions of cellular genes
  4. How can a proto-oncogene become an oncogene?
    1. Movement of DNA in the genome
    2. Amplification of proto-oncogene
    3. Point mutation in proto-oncogene
  5. Defects in ras gene and p53 gene can lead to cancer
    1. ras protein: protein that transmits signals within cells 
      1. defective ras protein= excessive cell division
    2. p53 gene: promotes synthesis of cell cycle
      1. defective p53 gene= uncontrollable cell cycle

Factors that Contribute to Cancer

  1. These factors may lead to cancer:
  • Genetics: if cancer runs in an individual's family, that individual may have cancer during his/her lifetime
  • DNA breakage: accumulation of damages and mutationsin DNA
  • Tumor viruses can interfere with gene regulation and cause cancer

Test Yourself

Stem cells are desirable for therapeutic use because...

  • they can develop into different tissue types
  • they alter genes involved in the cell cycle
  • they can produce genetically identical organisms
  • they are isolated from early embryos

What is an disadvantage of adult stem cells over embryonic stem cells?

  • Adult stem cells reproduce more rapidly than ES cells.
  • There is no difference between both cells; they are identical.
  • Adult stem cells are difficult to locate.
  • Adult stem cells are capable of differentiating into many different cell types.

The first organism to be cloned was a(n) ____________ and her name was _________.

  • cow; Mary
  • sheep; Dolly
  • cow; Dolly
  • sheep; Mary

The p53 protein normally promotes...

  • DNA replication
  • Cell division
  • Chromosome rearrangement
  • Apoptosis

TRUE or FALSE: DNA repair can contribute to the formation of cancer.

  • True
  • False