DNA TECHNOLOGY AND THE HUMAN GENOME
I.
In nature, bacteria can transfer DNA in three ways
a. Most of a bacterium’s DNA is found in a single bacterial
(prokaryotic) chromosome, which is a closed loop of DNA with
associated proteins
b. TRANSFORMATION  the taking up of DNA from the fluid
surrounding a cell
c. TRANSDUCTION  the transfer of bacterial genes by a phage
d. CONJUGATION  the union of bacterial cells and the DNA
transfer between them
II.
Bacterial plasmids can serve as carriers for gene transfer
a. Conjugation relies on the presence of an F factor
b. F FACTOR  “F” for fertility; a specific piece of DNA
i. Carries the information for sex pili and other proteins
ii. May exist integrated in bacteria chromosome OR AS A
iii. PLASMID  a small, circular DNA molecule separate
from the much larger bacterial chromosome
c. VECTOR  a plasmid carrying extra genes other than those
needed for replication and conjugation
d. R PLASMIDS  resistant to antibiotics
i. If you kill off all bacteria that are not resistant, only
bacteria containing R plasmids survive; making
antibiotics useless
III.
Plasmids are used to customize bacteria: An overview
a. A plasmid is first isolated from a bacterium
b. DNA carrying a gene of interest is obtained from another cell
c. A piece of DNA containing the gene is inserted into the plasmid
d. A bacterial cell takes up the plasmid by transformation
e. This genetically engineered, recombinant bacterium is then
cloned to generate many copies of the gene
IV.
Enzymes are used to “cut and paste” DNA
a. RESTRICTION ENZYMES  bacterial enzymes that act as
cutting tools for making recombinant DNA in a test tube
b. Bacteria contain these enzymes as protection against foreign
DNA
c. DNA LIGASE  “pasting” enzyme normally used in
replication
d. RECOMBINANT DNA  a DNA molecule carrying a new
combination of genes
V.
Genes can be cloned in recombinant plasmids: A closer look
a. Allows for the production of a desired gene on a large scale
b. A biologist can create cells to produce desired proteins in
marketable quantities
VI.
Cloned genes can be stored in genomic libraries
a. GENOMIC LIBRARY  the entire collection of cloned DNA
fragments in which the starting material is bulk DNA from
whole cells
VII. Reverse transcriptase helps make genes for cloning
a. Not all DNA is cloned directly from cells
b. Focusing on mRNA allows researchers only to deal with the
expressed portion of the gene
c. Reverse transcriptase is the key, it allows mRNA  DNA
d. cDNA  complementary DNA; the DNA that results from the
reverse transcription
e. These cDNA’s lack introns and are more efficient when
inserted into a bacterial genome
VIII. Nucleic acid probes identify clones carrying specific genes
a. PROBE  a labeled (radioactively) nucleic acid molecule used
to find a specific gene or other nucleotide sequence within a
mass of DNA
IX.
DNA microarrays test for the expression of many genes at once
a. DNA MICROARRAYS  enable scientists to assay the
expression of thousands of genes at once
b. Fluorescently labeled cDNA is used to study which genes are
active in a particular cell
X.
Gel electrophoresis sorts DNA molecules by size
a. GEL ELECTROPHORESIS  a method for physically sorting
macromolecules – proteins or nucleic acids – primarily on the
basis of their electrical charge and size
XI.
Restriction fragment analysis is a powerful method that detects
differences in DNA sequences
a. GENETIC MARKER  a chromosomal landmark whose
inheritance can be studied
b. RESTRICTION FRAGMENTS  pieces of DNA resulting
from the action of restriction enzymes
c. Different people will have different restriction fragments
d. Relatives will have more fragments in common then nonrelated individuals
e. Detecting harmful alleles
i. Since the alleles are different, the normal allele and the
disease causing allele will have different restriction
fragments
XII. The PCR method is used to amplify DNA sequences
a. PCR = Polymerase Chain Reaction
i. A technique by which any segment of DNA can be
amplified (cloned) in a test tube without using living cells
XIII. Most of the human genome does not consist of genes
a. 97 % of the 3 billion bases is non-coding
b. Most of which is “JUNK” DNA
c. “JUNK” DNA really means we don’t know its function
d. REPETITIVE DNA  nucleotide sequences present in many
copies in the genome
e. TELOMERES  repetitive DNA at the chromosome ends;
may have a protective function
f. JUMPING GENES = TRANSPOSONS
i. Segments of DNA that can insert in other locations
ii. May aid in genetic diversity and evolution
XIV. The Human Genome Project is unlocking the secrets of our genes
a. HGP = Human Genome Project
i. An effort to map the entire human genome
XV. DNA technology is used in courts of law
a. DNA FINGERPRINT  a specific pattern of bands (restriction
fragments)
XVI. Recombinant cells and organisms can mass-produce gene products
SOME PROTEIN PRODUCTS OF RECOMBINANT DNA
TECHNOLOGY
Product
Made In
Use
Human Insulin
E. coli
Treatment of diabetes
Human Growth
E. coli
Treatment for growth defects
Hormone (GH)
Epidermal Growth
E. coli
Treatment for burns, ulcers
Factor (EGF)
Interleukin-2 (IL-2)
E. coli
Possible treatment for cancer
Bovine Growth
E. coli
Improving weight gain in
Hormone (BGH)
cattle
Cellulase
E. coli
Breaking down cellulose for
animal feeds
Taxol
E. coli
Treatment for ovarian cancer
Interferons (alpha and
S. cerevisiae, E.
Possible treatment for cancer
gamma)
coli
and viral infections
Hepatitis B vaccine
S. cerevisiae
Prevention of viral hepatitis
Erythropoietin (EPO)
Mammalian cells
Treatment for anemia
Factor VIII
Mammalian cells
Treatment for hemophilia
Tissue Plasminogen
Mammalian cells
Treatment for heart attacks
Activator (TPA)
XVII. DNA technology is changing the pharmaceutical industry and
medicine
a. Therapeutic hormones
b. Diagnosis and treatment of disease
c. Vaccines
XVIII. Genetically modified organisms are transforming agriculture
a. GENETICALLY MODIFIED (GM) ORGANISMS  acquired
one or more genes artificially rather than breeding
b. TRANSGENIC ORGANISM  a recombinant organism with
a gene from another species
XIX. Gene therapy may someday help treat a variety of diseases
a. GENE THERAPY  alteration of an afflicted individual’s
genes
b. Many technical and ethical questions surround this concept
XX. Could GM organisms harm human health or the environment?
a. Is consuming “transgenic” crops in large amounts dangerous?
b. What are the negative effects, if any, on the ecosystem?
XXI. DNA technology raises important ethical questions
a. EUGENICS  the effort to control the genetic makeup of the
human populations
b. Too much information may lead to unintended negative effects
i. “Genetic Discrimination”