26.3 Gene Therapy & 26.4 Genomics and Bioinformatics
1. Testing DNA
a. “genetic markers” are abnormalities in the normal sequence of bases in a particular
chromosome are imaged (similar process to DNA “fingerprinting”)
b. DNA Microarrays: used to generate a person’s genetic profile (may become part of
regular medical check-ups in the future)
2. Gene Therapy
a. The insertion of genetic material into human cells for the treatment of genetic
disorders and various illnesses
b. Types:
i.
Ex Vivo method: literally means outside of living organism. Steps:
a. Remove bone marrow stem cells
b. Use retroviruses to bring the normal gene into the bone marrow stem
cells
c. Viral recombinant DNA carries normal gene into genome
d. Return genetically engineered cells to patient
ii.
In Vivo method: literally means inside of living organism
a. Many diverse methods of treatment
b. Can include direct injections into bone marrow (spinal tap)
3. Sequencing the Genome: The Human Genome Project
i.
Human genome has 3.2 billion pairs of DNA bases (6 feet long per cell)
ii.
Took 13 years to complete
iii.
Human have 20 000 – 25 000 genes
iv.
Now takes about 3 weeks to sequence an entire genome
v.
Opened up many possibilities for research and treatment
vi.
Led to discovery of many small regions of DNA that vary among people
(polymorphisms)
vii.
Single nucleotide polymorphisms (SNP) can have no effect, but some have
change protein coding
viii.
Led to “designer drugs”: drugs made specifically to an individual’s genotype
ix.
Most of the genome codes for a gene, but some doesn’t. This so-called
“junk” DNA is now the focus of some researchers
4. Genome Architecture
a. 99% of human genome is DNA that does not directly code for amino acid sequences
b. Some is used to make ribomsomes and tRNA, some are transposons, some repetitive
DNA elements, and sequences of unknown function
c. Transposons:
a. Discovered by Barbara McClintock in 1950 (won Nobel Prize)
b. Short sequences of DNA that are able to jump from one location to another
c. May alter neighbouring genes, often decreasing their expression
d. Act like a regulator gene
d. Repetitive Elements
a. Nearly ½ the human genome
b. Mostly unknown function
c. Centromeres and telomeres made of these
d. May help to maintain structural stability
5. What is a Gene?
a. Historical definition: a particular location on a chromosome to being much
more complex in eukaryotes
b. Genes are seemingly randomly distributed along a chromosome, fragmented
into exons (the part that is spliced after transcription that leaves the nucleus)
between mostly introns (stays in the cell)
c. Over 95% of human genes are introns
d. Introns likely have a significant role in gene regulation
e. Modern definition: moving away from location and focusing on the results of
transcription. Mark Gerstein suggests, “A gene is a genomic sequence (either
DNA or RNA) directly encoding functional products, either RNA or protein.”
Takes into account:
i. Gene product may not necesarrily be a protein
ii. Gene may not be found at a particular location on a chromosome
iii. Genetic material need not only be DNA (some prokaryotes have RNA
genes)
6. Functional and Comparative Genomics:
a. Genomics: the study of the complete genetic sequences of organisms
b. Compartive Genomics: comparing the human genome to other organisms
i. allows for model organisms to be research subject. E.g. fruitfly
(Drosphilia melanogaster) inserted with human gene associated with
Parkinson disease
ii. advantage is shorter lifespan, so quicker results
iii. more ethical than inserting genes into humans
iv. allows us to understand evolutionary relationships among organisms.
E.g. genomes of all vertebrates are very similar
1. humans and chimpanzees are 98% alike
2. humans and mouse are 85% alike
c. Functional Genomics: understanding the function of each gene and how genes
interact
i. Uses DNA microarrays
ii. Allows for generation of genetic profile of individual
d. Proteomics: the study of structure, function, and interaction of cellular proteins
e. Bioinformatics: the application of computer technologies to study biological
information that allows for collection and analysis of genomic and proteomic
information
p.536 #1,2
“Testing Yourself” p. 538 #1-3, 7-11, 14-15