human genetics .... by hashim

8/3/2019 Human Genetics .... by hashim

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2000 Timothy G. Standish

Human Genetics

Timothy G. Standish, Ph. D.


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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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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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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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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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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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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.



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.




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




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.




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.




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




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.




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.




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.



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human genetics .... by hashim

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