Human Genetics Traits

NAME:______PERIOD:_____DATE:______

Lab: Human Genetic Traits

Directions: This exercise deals with the action of human genes on desecrate, easily observable traits. You will make observations of these traits in yourself and in your classmates to gain an understanding of how particular genes are expressed in humans. These traits are known as single-gene traits, which are the expressions of two alleles at one gene locus. Have another student check you for each of the traits listed in the table below. Record in the table on the next page your results. Under phenotype list if you are dominant or recessive for the trait and under genotype list possible combinations of genes.

TRAIT DOMINANT RECESSIVE Bent Pinky (B, b) Last joint is bent Last joint is straight Skin Color (S, s) Dark colors Light colors Freckles (F, f) Present Absent Earlobe (E, e) Unattached Attached Tongue Rolling (R, r) Can roll edges of tongue Can’t roll edges of tongue Widow’s Peak (W, w) Present Absent Thumb Crossing (T, t) Left thumb over right Right thumb over left Mid-Digital Hair (M, m) Hair on mid-digit No hair Cleft Chin (C, c) Indentation in middle No indentation Eyebrows (E, e) Eyebrows not connected Eyebrows connected Hitchhiker’s Thumb (H, h) Low degree angle 90-degree angle Dimples (D, d) Present Absent PTC Tasters (P, p) Taster Non-taster Sodium Benzoate (S, s) Taster Non-taster Thiourea (T, t) Taster Non-taster

1 Your Genetic Traits

Your Parents TRAIT Phenotype Genotype Phenotypes Mom Dad

Bent Pinky (B, b)

Skin Color (S, s)

Freckles (F, f)

Earlobe (E, e)

Tongue Rolling (R, r)

Widow’s Peak (W, w)

Thumb Crossing (T, t)

Mid-Digital Hair (M, m)

Cleft Chin (C, c)

Eyebrows (E, e) Hitchhiker’s Thumb (H, h)

Dimples (D, d)

PTC Tasters (P, p)

Sodium Benzoate (S, s)

Thiourea (T, t)

2 Class Results

TRAIT DOMINANT RECESSIVE Bent Pinky (B, b) Skin Color (S, s) Freckles (F, f) Earlobe (E, e) Tongue Rolling (R, r) Widow’s Peak (W, w) Thumb Crossing (T, t) Mid-Digital Hair (M, m) Cleft Chin (C, c) Eyebrows (E, e) Hitchhiker’s Thumb (H, h) Dimples (D, d) PTC Tasters (P, p) Sodium Benzoate (S, s) Thiourea (T, t)

Questions: 1. How many dominant phenotype traits do you have? ______List which traits are dominant.

2. How many recessive phenotype traits do you have? ______List which traits are recessive.

3 3. Are phenotypes for some traits clearly more abundant than the alternate phenotypes for these traits? ______Why do you believe this is true?

4. Some human traits can be changed by human intervention and some cannot. Provide examples of each of these types of traits.

5. You probably already know that some traits are genetic and others are environmental. But most human traits reflect an interaction between genetic and environmental factors. Name some traits that might fall into this category and explain why you think they do.

6. Describe some of the benefits of human genetic variation. What are some of the potential problems that it can cause?