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Chapter 1

BIOL 600 Chapter Notes - Chapter 1: Albinism, Dominance (Genetics), Ultraviolet

Course Code
BIOL 600

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Introduction to Genetics
Albinism: Defect in one of the enzymes required to produce melanin (darkens our skin, hair)
which normally protects the DNA of skin cells from ultraviolet radiation and helps with eyesight.
-Is an autosomal recessive trait, someone must receive a copy from each parent.
-Several different genes that control the synthesis and storage of melanin; many different types
of mutations can occur at each gene, any one of which may lead to albinism.
-Hundred times more frequent in Hopis population
-More frequent because albinism was seen in high regard. Albino male members were allowed
to stay behind while other men went out in the sun (protected and more mating opportunities.)
Genome: A complete set of genetic instructions for any organisms.
Three major sub disciplines of genetics
1. Transmission genetics: Basic principles of heredity and how traits are passed from one
generation to the next. Focus is on the individual organism.
2. Molecular genetics: Chemical nature of the gene itself: how genetic information is
encoded, replicated, and expressed. Focus is on the gene.
3. Population genetics: How genetic composition of groups changes geographically and
with the passage of time.
Model genetic organisms
-Organisms having characteristics that make them particularly useful for genetic analysis and
which a tremendous amount of genetic information has accumulated.
Six model organisms:
Fruit fly
Nematode worm
Thale-cress plant
House mouse
Bakers yeast
Good candidates because:
Short generation time
Large but manageable number of progeny
Adaptability to a lab environment
Old theories:
Pangenesis: Gemmules carry information from various parts of the body to the reproductive
organs, where they are passed to the embryo at conception.
Inheritance of acquired characteristics: Traits acquired in a person’s lifetime become
incorporated into that person’s hereditary information and passed on to offspring.
Preformationism: Inside the egg or sperm there exists a fully formed miniature adult, a
homunculus. Meant that traits came from one parent.
Blending inheritance
Current theories:
Germ-plasm theory: Cells in the reproductive organs carry a complete set of genetic information
that is passed to the egg and sperm.
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