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2000 Timothy G. Standish
Human Genetics
Timothy G. Standish, Ph. D.
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2000 Timothy G. Standish
The Madness of King George IIIPartly as a result of the erratic behavior of King
George III the American colonies decided to breakaway from the United Kingdom
Other members of King Georges family also
exhibited strange behavior with dire consequences.These included Mary Queen of Scots and her son
James I both of whom were beheaded.
Because madness seems to have run in the family, itis thought thought to have a genetic basis
Acute intermittent porphyria seems to be consistent
with the symptoms exhibited by George III
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2000 Timothy G. Standish
Human Heredity Is Not Unique
The genes of humans behave in the same way asgenes of other organisms
Of the estimated 100,000 human genes, most are
identical in all humansThe relatively small number of polymorphic
genes in humans account for only part of the
variability that we see between humans
While each human (except for identical twins)
has a unique set of genetic information, variation
between humans also results from differences in
the environment
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2000 Timothy G. Standish
Politics and GeneticsBecause we are talking about how humans are when
we are talking about human genetics, there can be
lots of controversy when traits are seen as relating to
race, gender or other sensitive issues
This is particularly true when we start to talk about
the genetics of behavior
Nazis and other extreme right wing politicians see
human worth and behavior being based on genetics
Communists and other extreme leftwing politicians
see humans as infinitely pliable and molded by their
environment not genetics
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2000 Timothy G. Standish
Specific Human TraitsAlbinism - There are a number of different
types of albinism, but each is characterized byan absence of pigment from the skin, eyes andhair. Albino individuals typically have very pale
white skin, light blue or pink eyes, and lightblond or white hair. Albinism is a recessivetrait.
Baldness - Loss of hair from the scalp followingpuberty. A sex influenced trait that is mostcommonly fully expressed (as a dominant trait)in males, but carried on an autosome.
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2000 Timothy G. Standish
Specific Human Traits
Bent little finger - The little finger noticeablycurves toward the other fingers. Bent isdominant to straight.
Brown teeth - Teeth have a brown color thatis not the result of poor oral hygiene orantibiotics taken as a child. White teeth aredominant.
Cleft chin - A noticeable indentation at thecenter of the chin. For examples think of KirkDouglas and Michael Jackson (after plasticsurgery). Having a cleft chin is dominant to a
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Specific Human Traits
Color blindness - Inability to distinguishbetween colors of the same intensity.
There may be two types, red green color
blindness in which individuals perceivered and green as the same color, andcomplete color blindness in which all
colors are perceived as being the sameand vision is the functional equivalent ofblack and white television. Both types of
colorblindness are sex linked traits.
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Dimples - Round indentations in the cheekswhen smiling, not lines or clefts.
Double-jointed thumbs - This is commonly
called a hitchhiker's thumb. The thumb canbend back at almost 90 degrees. Hitchhiker'sthumb is a recessive trait, but it may vary in itsexpression.
Ear lobes attached - The lobes at the bottomof the ear are either not present, or areattached to the side of the head on their full
length. Attached is recessive.
Specific Human Traits
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Eye color - Eye color may vary from violet to brightblue to gray. Other eye colors include green, brown,black, and yellow. Albinos may have red eyes asalbino laboratory white rats do. Eye color is
determined by two traits, one that controls thetexture of the iris and a second determining therelative abundance of a brown pigment calledmelanin. The surface of the iris determines the
blueness of the eyes. When a small amount ofmelanin is present, green eyes result while brownand black eyes result from relatively increasingamounts of melanin. For the purposes of this
exercise, determine the presence or absence of
Specific Human Traits
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Index finger shorter than ring finger - Theindex finger (next to your thumb) is longerthan the ring finger (next to your little finger).This is a sex influenced trait. Check theclass data to see if the frequency is differentfor the different sexes.
Freckles - Small patches of darkerpigmented skin on various parts of the bodyand most visible in those areas commonlyexposed to the sun. These may be present
on both dark and light skinned individuals.
Specific Human Traits
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Hair color - The wonders of modern technology
have provided many ways in which phenotypecan be altered. Hair color is the mostcommonly altered phenotype. Record your true
unaltered phenotype unless your hair hasturned gray or white in which case the colorbefore it changed should be recorded. Multiple
alleles control hair color.Hair whorling These may be referred to ascowlicks. Areas in which hair grows from your
scalp in a whorl instead of in a given direction.
Specific Human Traits
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Hand folding - When the hands are foldedeither the left or right thumb will be on top.Record which thumb feels most natural ontop. Left thumb on top is dominant.
Mid-digital hair - Hair growing from themiddle section of each finger. Hair presenceis dominant.
Myopia - Short sightedness, the inability tosee far off objects without correction byglasses or contacts. If you have had surgery
to correct this problem, record yourself as
Specific Human Traits
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Polydactyly - Having more than fivedigits on each hand and foot.
PTC tasting - Phenylthiocarbamide
(PTC) is a bitter tasting chemical thatcannot be tasted by some individuals.Paper with PTC on it will be provided.Place a small piece in your mouth. Ifyou taste a distinct bitter taste, you arepositive for PTC tasting. Tasting isdominant to the inability to taste PTC.
Specific Human Traits
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S-methyl thioester smeller - S-methyl
thioesters are produced in urine following theconsumption of asparagus. Some individualscannot smell this substance. Eat at least five
spears of asparagus then note down anyunusual odor the next time you urinate. If yousmell a strong odor on urination, you are an S-
methyl thioester smeller.Tongue rolling - Tongue rolling is the abilityto form a tube with your tongue. Rolling is
dominant.
Specific Human Traits
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Tongue rolling - Tongue rolling is the abilityto form a tube with your tongue. Rolling isdominant.
White forelock - A white patch of hair at thefront of the scalp.
Widow's peak - A sharp point in the hairline
that points toward the nose. Having awidow's peak is dominant to a smoothhairline.
Specific Human Traits
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