Unnatural Selection: Chapter 11

Lots of interesting insets and boxes today. Here are a few.

1. A rough history of genetics (paraphrased)

• 1860s - Mendel.
• 1870s - Darwin. Books: Origin of Species and Descent of Man.
• 1910s - eugenics.
• 1920s - Thomas Hunt Morgan, heredity and fruit flies.
• 1930s - hemophilia and color-blindness figured out as sex-linked conditions.
• 1950s - Watson and Crick! Genetic linkage as well.
• 1960s - hybrid cells made (mixed-source DNA).
• 1970s - sequenced: viral protein coat gene. Endonuclease roles elaborated.
• 1980s - Human Genome Project begun. In Paris: gene-fragment library founded.
• 1990s - genome mapping!
  

2. Mendel's principles (verbatim), now discovered to have many exceptions:

• Traits are inherited as units, as if they are particles. They are inherited in pairs.
• Some traits are dominant, or overpowering, while others recede, are recessive [sic].
• If each parent has one dominant and one recessive particle, three-fourths of the offspring will show the dominant trait and one-fourth will show the recessive trait.
• Many traits are inherited independently of each other. Thus, plants may be of similar height, but the color of their blossoms may vary. Some traits are unvarying within a certain hereditary line, but other traits vary independently.
  

3. So-called junk DNA and a discussion of its supposed roles in macro- and micro-evolution.

• After years of fiddling, we still don't know what much of this non-gene (perhaps 95% of the total genome) sequence is or does.
• It does have functions like specifying proteins' 3-D shapes and helping us identify mammal cells.
• "It seems that most genes may have several corresponding pseudogenes - misguided ancestors, perhaps, who have lost their way in the genome and can't get back home." If macroevolution is fact, why the need to use so many qualifying words? Perhaps? Maybe? Could? Conceivably?
  

4. Polymerase chain reaction (PCR).

• The enzyme: DNA polymerase, a.k.a. the copying enzyme.
• The method: Use a DNA polymerase from a heat-loving bacterium; the heat separates the freshly made copies of a DNA fragment so the enzyme can copy it again.
• "It's sometimes also possible to extract DNA from a fingerprint." Now that would help Scotland Yard, wouldn't it.