GENETICS 1 What is Genetics? The Study of similarities and differences between relatives. What is it that elephants have that no other animal has? What is Genetics? The study of similarities and differences between relatives. What is it that elephants have that no other animal has?
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The Study of similarities and differences between
What is it that
that no other
The study of similarities and differences between
What is it that
that no other
produce the differences we see?
Archeological evidence from 8,000 – 1,000 B.C. shows horses, camels, and oxen had been domesticated and that various breeds of dogs had derived from wolves, through artificial selection.
Pre-formationism – sex cells contain a complete miniature adult (the homunculus)
Epigenesis – presumably put forth by Harvey, held that body structures were not present in the sex cells, but were formed anew.
[the notion was discredited by August Weissman, who cut tails off mice for 22 generations and continued to get mice with long tails]
In a simple case, shown here are 2 versions of a “gene”. Where the flower of the pea plant is yellow (due to gene y) or purple (due to gene Y). Many genes have hundreds of alternatives, and might be expressed thus: Y1, or Y2, or Y3, or Y4, orY5, etc.
Species Genes DNA (bp)
E. coli (bacterium) 4,400 4,600,000
Yeast cell 6,000 12,000,000
Roundworm 19,000 97,000,000
Fruit fly 13,600 165,000,000
Rice plant 55,000 466,000,000
Gallus gallus (Chicken) 23,000 1,000,000,000
Rat 30,000 2,750,000,000
Homo sapiens (human)25,000 3,200,000,000
Amoeba proteus (amoeba) ? 290,000,000,000
1. Structural – involved in building and maintaining subcellular structures.
2. Functional – enzymes.
DNA in the nucleus of the cell
makes a nearly identical copy
of itself and transports this copy
to the site of protein synthesis in
the cell. Using the genetic code,
the message originally present
in the DNA and transcribed into
the RNA copy is translated into
a protein. This process takes only
seconds to accomplish since it is
aided by enzymes.
… THE CAT SAW THE RAT …
We have just completed sequencing the entire human genome and there are exactly 3.164 billion base pairs in the human genome.
The best estimate is that there are only 25,000 genes, half of which we don’t yet know the function.
The rest consists of highly repetitive sequences (e.g., TTTGGCTTTGGCTTTGGC) repeated over and over thousands of times.
Almost 99.9% of the base pairs are exactly the same in all people! (This still leaves about 3 million base pairs that differ among any two individuals) Focus on the similarities…
The genome is full of non-coding or “Junk” or repetitive DNA – but even this can be useful for DNA Fingerprinting.
Can help to convict the guilty and exonerate the innocent.
In a famous case in England, a rapist was caught 3 yrs after the crime when DNA from the sperm was matched with his DNA.
The first organism to have its genetic material completely sequenced was a bacterial virus (ΦX174). It has 5,386 base pairs. Using this information, researchers 2 years ago synthesized a completely artificial virus from lab chemicals that was 100% identical to the natural ΦX174 virus; and it was able to behave like the natural virus – infecting a bacterial cell. We have created life in a test tube… or at least…..duplicated it!
We can isolate individual genes from any organism or individual.
We can make millions of copies of that gene in a matter of hours.
We can combine that gene with others in what is called a Recombinant DNA molecule and insert that into most any organism we choose. This is called Genetic Engineering
Human insulin produced
in a bacterium using a
gene obtained from humans.
SCID (severe combined immunodeficiency disease) is a fatal condition due to the absence of an enzyme, adenine deaminase or ADA.
The gene for ADA has been isolated, combined with a harmless virus (Recombinant DNA) and introduced into children with this condition. The photo on the right shows one successful application of this technology.
Performance-enhancing drug use has become a big problem in both professional and amateur athletics. Periodic testing for these drugs probably reduces their use somewhat.
What if athletes began to use “gene doping”, where genes for Human Growth Hormone (HGH) or Insulin-like Growth factor (IGF-1) would be introduced into their muscles? It would be more effective and essentially non-detectable. Olympic officials are definitely worried about this happening – fearing it has the potential to ruin athletic competition as we know it.
A gene for insect resistance (Bt) has been engineered into most all of the corn we consume, rendering it quite resistant to the European corn borer.
Many other fruits and vegetables have been engineered for drought and cold resistance and resistance to plant diseases.