Name:________________________________________________________  Period:_________

 

MAKING YOUR OWN GENETIC PROFILE

Procedure:

1.      Look at the list of traits below. With the help of classmates, try to determine what your phenotype is for each of the traits. (Example: Are your earlobes attached of free?) Record in Table 1.

2.      Determine if each of the traits you have is dominant or recessive. This information is in the list of traits below. Record in Table 1.

3.      Try to determine your genotype. If the trait you have is recess, then you are homozygous recessive (Example: bb). If the trait you have is dominant, then you are either homozygous dominant or heterozygous dominant. You won’t know which one unless you make a pedigree of your family so put both of the possible genotypes if you are dominant (Example: BB or Bb).

LIST OF HUMAN TRAITS

1.      FREE OR ATTACHED EARLOBES: In most people the dominant allele makes the earlobes hang free (F), but when a person is homozygous for a certain allele, the earlobes are attached (f) directly to the side of the head so that there is no lobe hanging free. Determine your phenotype (with the help of your classmate).

 

2.      PRESENCE OR ABSENCE OF A WIDOW’S PEAK: In some people the hair line drops downward and forms a distinct point in the center of the forehead known as a widow’s peak (W) and results from a dominant allele. If a person inherits the recessive allele, then their hair grows in a continuous line across their forehead and has no widow’s peak (w). Determine your phenotype.

 

 

3.      ABILITY TO ROLL TONGUE: A dominant allele gives some people the ability to roll (R) their tongue into a distinct U-shape when the tongue is extended from the mouth. Others who cannot roll their tongue and can only produce a slight downward curve of the tongue when it is extended from the mouth. Non-rollers (r) results from a recessive allele. Determine your phenotype.

 

 

 

4.      BENT OR STRAIGHT LITTLE FINGER: A dominant allele causes the last join of the little finger to bend inward toward the fourth finger. Lay both hands flat on a table or desk, relax the muscles of your hand and note whether you have a bent (B) or straight (b) little finger. Determine your phenotype.

 

5.      PRESENCE OR ABSENCE OF DIMPLES: Some people have anywhere from light to very deep indentations in their cheeks when they smile called dimples. Sometimes they will have an indentation in only one cheek but they still have dimples. Having dimples (d) is recessive to no dimples (D). Determine your phenotype.

 

 

6.      PIGMENTED OR UNPIGMENTED IRIS OF THE EYES: When a person is homozygous for a certain recessive trait there is no pigment in the front part of the eye and the blue layer at the back of the eye show through. These people have blue eyes and are said to have unpigmented (p) eyes. A dominant allele causes pigment to be deposited in the front layer of the iris and masks the blue to a varying degree and show up as black, brown, hazel or green eyes. These people are said to have pigmented (P) eyes. Determine your phenotype.

 

7.      PRESENCE OR ABSENCE OF MID-DIGITAL HAIR: Some people have hair in between the first and second joints on the fingers while others do not. The presence of mid-digital hair (M) on ANY of your fingers is caused by a dominant allele. No mid-digital hair (m) from all the fingers is due to a recessive allele. This hair may be very fine and you should look very carefully on ALL your fingers before deciding your phenotype.

 

8.      2ND FINGER SHORTER THAN THE 4TH: Hold your fingers together and place your hand down on a sheet of paper so that the fingers are perpendicular to a horizontal line on the paper. Move your hand up or down until the tip of the fourth (ring) finger touches a line. If you have a shorter 2nd finger (S), this is caused by a dominant allele and if you have a shorter 4th finger (s), this is caused by a recessive allele. Determine your phenotype.

 

9.      LEFT OR RIGHT THUMB ON TOP WHEN CROSSING: Take your hands and cross them. Having your left (L) thumb on top is caused by a dominant allele and having your right (l) thumb on top is caused by a recessive allele. Determine your phenotype.

 

 

10.  PRESENCE OR ABSENCE OF CLEFT CHIN: Some people have a small indentation in their chin known as a cleft chin. Other people have a rounded chin with no indentation. Having a cleft chin (c) is recessive to no cleft chin (C). Determine your phenotype.

 

11.  PRESENCE OR ABSENCE OF HITCHHIKER’S THUMB: Hold your hand in a fist and stick your thumb out as if you are hitchhiking. If your thumb bends at the joint then you have hitchhiker’s thumb (h) which is caused by a recessive allele. If your thumb does not bend at the joint but remains straight then you have the dominant no hitchhiker’s thumb (H). Determine your phenotype.

 

 

12.  PRESENCE OR ABSENCE OF FRECKLES: Freckles are small brown dots of pigmentation usually located across the bridge of the nose and cheeks of the face. Having freckles (n) is caused be a recessive allele whereas no freckles (N) is caused by a dominant allele. Determine your phenotype.

 

13.  P.T.C. TASTER: Some people can taste a chemical known as P.T.C. (phenylthiocarbamide) while others detect no taste at all. This chemical is entirely harmless. Place a small piece of filter paper treated with P.T.C. on your tongue but do not swallow it. If you detect no taste other than the taste of the filter paper itself then you are homozygous recessive and a P.T. C. non-taster (p). If you do taste the chemical, you are known as a P. T. C. taster (P) and this is caused by a dominant allele. Do not report a taste if you are at all doubtful about it. If you are a taster, you will know it!!!!!! Determine your phenotype.

 

14.  SODIUM BENZOATE TASTER: Some people can taste a chemical known as sodium benzoate while others detect no taste at all. This chemical is entirely harmless. Place a small piece of filter paper treated with sodium benzoate on your tongue but do not swallow it. If you detect no taste other than the taste of the filter paper itself then you are homozygous recessive and a sodium benzoate non-taster (s). If you do taste the chemical, you are known as a sodium benzoate taster (S) and this is caused by a dominant allele. Do not report a taste if you are at all doubtful about it. Determine your phenotype.

 

15.  THIOUREA TASTER: Some people can taste a chemical known as thiourea while others detect no taste at all. This chemical is entirely harmless. Place a small piece of filter paper treated with thiourea on your tongue but do not swallow it. If you detect no taste other than the taste of the filter paper itself then you are homozygous recessive and a thiourea non-taster (t). If you do taste the chemical, you are known as a thiourea taster (T) and this is caused by a dominant allele. Do not report a taste if you are at all doubtful about it. Determine your phenotype.

 

 

 

 

TABLE 1:

Trait

Your phenotype

Is your phenotype dominant or recessive?

Your possible genotype(s)

1.       FREE OR ATTACHED EARLOBES

 

 

 

2.        WIDOW’S PEAK OR NO WIDOW’S PEAK:

 

 

 

 

3.       ROLL TONGUE OR NON-ROLLER

 

 

 

 

4.       BENT OR STRAIGHT LITTLE FINGER:

 

 

 

5.       DIMPLES OR NO DIMPLES:

 

 

 

 

6.        PIGMENTED OR UNPIGMENTED IRIS OF THE EYES:

 

 

 

7.       MID-DIGITAL HAIR OR NO MID-DIGITAL HAIR:

 

 

 

8.       SHORT 2ND FINGER OR SHORT 4TH FINGER:

 

 

 

9.       LEFT OR RIGHT THUMB ON TOP WHEN CROSSING:

 

 

 

10.    CLEFT CHIN OR NO CLEFT CHIN:

 

 

 

 

11.    HITCHHIKER’S THUMB OR NO HITCHHIKER’S THUMB:

 

 

 

12.    FRECKLES OR NO FRECKLES

 

 

 

 

13.    P.T.C. TASTER OR NON-TASTER:

 

 

 

 

14.    SODIUM BENZOATE TASTER OR NON-TASTER:

 

 

 

15.    THIOUREA TASTER OR NON-TASTER:

 

 

 

 

 

Questions:

1.      What is a phenotype?

 

2.      How can you determine your phenotype?

 

 

3.      How many of your traits are the dominant phenotype?

 

4.      How many of your traits are the recessive phenotype?

 

 

5.      What is a genotype?

 

6.      What is the genotype of a person who is a P.T.C. non-taster?

 

 

7.      Why can you easily figure out your genotype if you have a recessive trait?

 

 

8.      What are the two possible genotypes for a person that does not have hitchhiker’s thumb?

 

9.      Why is it difficult to figure out your genotype if you have a dominant trait?

 

10.  What could you (a Freshmen in high school) do to figure out which of the genotypes in question #8 is most likely correct if you are a person that does not have hitchhiker’s thumb?