Transcript Human Genetics

Human Genetics
Timothy G. Standish, Ph. D.
©2000 Timothy G. Standish
The Madness of King George III
Partly as a result of the erratic behavior of King
George III the American colonies decided to break
away from the United Kingdom
Other members of King George’s 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, it
is thought thought to have a genetic basis
Acute intermittent porphyria seems to be consistent
with the symptoms exhibited by George III
©2000 Timothy G. Standish
Human Heredity Is Not Unique
The genes of humans behave in the same way as
genes of other organisms
Of the estimated 100,000 human genes, most are
identical in all humans
The 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
©2000 Timothy G. Standish
Politics and Genetics
Because 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
©2000 Timothy G. Standish
Specific Human Traits
Albinism - There are a number of different
types of albinism, but each is characterized by
an absence of pigment from the skin, eyes and
hair. Albino individuals typically have very pale
white skin, light blue or pink eyes, and light
blond or white hair. Albinism is a recessive trait.
Baldness - Loss of hair from the scalp following
puberty. A sex influenced trait that is most
commonly fully expressed (as a dominant trait)
in males, but carried on an autosome.
©2000 Timothy G. Standish
Specific Human Traits
Bent little finger - The little finger noticeably
curves toward the other fingers. Bent is
dominant to straight.
Brown teeth - Teeth have a brown color that
is not the result of poor oral hygiene or
antibiotics taken as a child. White teeth are
dominant.
Cleft chin - A noticeable indentation at the
center of the chin. For examples think of Kirk
Douglas and Michael Jackson (after plastic
surgery). Having a cleft chin is dominant to a
©2000 Timothy G. Standish
Specific Human Traits
Color blindness - Inability to distinguish
between colors of the same intensity.
There may be two types, red green color
blindness in which individuals perceive
red and green as the same color, and
complete color blindness in which all
colors are perceived as being the same
and vision is the functional equivalent of
black and white television. Both types of
colorblindness are sex linked traits.
©2000 Timothy G. Standish
Specific Human Traits
Dimples - Round indentations in the cheeks
when smiling, not lines or clefts.
Double-jointed thumbs - This is commonly
called a hitchhiker's thumb. The thumb can
bend back at almost 90 degrees. Hitchhiker's
thumb is a recessive trait, but it may vary in its
expression.
Ear lobes attached - The lobes at the bottom
of the ear are either not present, or are
attached to the side of the head on their full
length. Attached is recessive.
©2000 Timothy G. Standish
Specific Human Traits
Eye color - Eye color may vary from violet to bright
blue to gray. Other eye colors include green, brown,
black, and yellow. Albinos may have red eyes as
albino laboratory white rats do. Eye color is
determined by two traits, one that controls the
texture of the iris and a second determining the
relative abundance of a brown pigment called
melanin. The surface of the iris determines the
blueness of the eyes. When a small amount of
melanin is present, green eyes result while brown
and black eyes result from relatively increasing
amounts of melanin. For the purposes of this
exercise, determine the presence or absence of
©2000 Timothy G. Standish
Specific Human Traits
Index finger shorter than ring finger - The
index finger (next to your thumb) is longer
than the ring finger (next to your little finger).
This is a sex influenced trait. Check the
class data to see if the frequency is different
for the different sexes.
Freckles - Small patches of darker
pigmented skin on various parts of the body
and most visible in those areas commonly
exposed to the sun. These may be present
on both dark and light skinned individuals.
©2000 Timothy G. Standish
Specific Human Traits
Hair color - The wonders of modern technology
have provided many ways in which phenotype
can be altered. Hair color is the most
commonly altered phenotype. Record your true
unaltered phenotype unless your hair has
turned gray or white in which case the color
before it changed should be recorded. Multiple
alleles control hair color.
Hair whorlingThese may be referred to as
cowlicks. Areas in which hair grows from your
scalp in a whorl instead of in a given direction.
©2000 Timothy G. Standish
Specific Human Traits
Hand folding - When the hands are folded
either the left or right thumb will be on top.
Record which thumb feels most natural on
top. Left thumb on top is dominant.
Mid-digital hair - Hair growing from the
middle section of each finger. Hair presence
is dominant.
Myopia - Short sightedness, the inability to
see far off objects without correction by
glasses or contacts. If you have had surgery
to correct this problem, record yourself as
©2000 Timothy G. Standish
Specific Human Traits
Polydactyly - Having more than five
digits on each hand and foot.
PTC tasting - Phenylthiocarbamide
(PTC) is a bitter tasting chemical that
cannot be tasted by some individuals.
Paper with PTC on it will be provided.
Place a small piece in your mouth. If
you taste a distinct bitter taste, you are
positive for PTC tasting. Tasting is
dominant to the inability to taste PTC.
©2000 Timothy G. Standish
Specific Human Traits
S-methyl thioester smeller - S-methyl
thioesters are produced in urine following the
consumption of asparagus. Some individuals
cannot smell this substance. Eat at least five
spears of asparagus then note down any
unusual odor the next time you urinate. If you
smell a strong odor on urination, you are an Smethyl thioester smeller.
Tongue rolling - Tongue rolling is the ability to
form a tube with your tongue. Rolling is
dominant.
©2000 Timothy G. Standish
Specific Human Traits
Tongue rolling - Tongue rolling is the ability
to form a tube with your tongue. Rolling is
dominant.
White forelock - A white patch of hair at the
front of the scalp.
Widow's peak - A sharp point in the hairline
that points toward the nose. Having a
widow's peak is dominant to a smooth
hairline.
©2000 Timothy G. Standish