Variations on a Human Face Lab

Transcription

1 Variations on a Human Face Lab Introduction: Have you ever wondered why everybody has a different appearance even if they are closely related? It is because of the large variety or characteristics that exist in the human population. This lab will demonstrate this concept. You are to be parent and you are going to make a baby. What would your baby look like if you and your partner spouse both typically have one dominant and one recessive gene for each of the following features of the face? Objective: The student will determine the appearance of their child s face. By flipping coins the student will determine the bits of information that will contribute to the complete appearance of the child s face. Materials: 2 coins (pennies) 2 students Handout of the Traits White paper Colors Pencils, crayons, or markers Procedure: 1. First determine which partner will toss for the male and which will toss for the female. Each of you will get a penny. (You will have the opportunity to make 2 children you will pick which one you would like to draw) 2. Have the partner who is representing the male flip the coin, if the coin lands heads up, the offspring is female, if tails, the offspring is male. What is the sex of your offspring? 3. For all coin tosses from now on. Heads will represent the dominant allele and tails will represent the recessive allele. For each trait on the chart you will flip a coin to determine what GENOTYPE your offspring will have. Write the allele that mom and dad both give in the correct area of the chart and the genotype of the child next to each trait given. 4. Complete the traits in the chart first. Then complete the polygenic traits.

2 Polygenic Traits Some traits are controlled by more than one gene and are called polygenic. Hair, eye color and skin color are examples of polygenic traits. To determine the color of your child s hair and eyes, you will flip your coins twice, once to represent the A gene, and once to represent the B gene. Example: Flip 1 Head / Head Flip 2 Head / Tail Genotype A A B b 4. Hair Color -- What did you flip? Flip 1 Flip 2 Possible genotypes and hair color. If the genotype is. AABB AABb AAbb AaBB Aabb AaBb aabb aabb aabb The hair color is black black red regular blonde dark blonde regular blonde pale yellow blonde 5. Eye Color -- What did you flip? Flip 1 Flip 2 If the genotype is. AABB AABb AAbb AaBB AaBb Aabb aabb aabb aabb The eye color is. dark dark with green flecks gray-blue green dark blue light blue (hazel) 6. Skin Color skin color is controlled by a lot of different genes that basically add together to determine how dark the skin is and variations in tone. To simulate how skin color might be determined. Flip a single coin 10 times. Each time the coin turns up heads, give your offspring a point. Add your points together. 10 pts would be a very dark child and 1 pt would be a very pale child. How many points does your child have?

3 DRAW YOUR CHILD Now that you have determined all the traits of your child, draw a picture. Use colors and try to make the sketch as accurate as possible given the traits your child inherited. Make sure you name your child too! Analysis and Conclusions 1. What are the odds that your child will be a boy? Which parent determines the sex of the child? 2. In your cross, both of the parents have wavy hair and round faces. How is it possible that the child of this cross could have neither of these traits? 3. Which traits are codominant or incompletely dominant? (these traits don t have a clear dominant or recessive, the heterozygous condition shows a blending or a middle condition). List at least three. 4. Why did you have to flip the coin twice to determine hair and eye color? 5. Show the cross of a wavy haired person with a wavy haired person. Use a Punnet square. What percentage of the offspring will have straight hair? What percentage of the offspring will have wavy hair? What percentage of the offspring will have curly hair? *What type of hair did your child have?

4 Biology Parents: Variations on a Human Face Lab CHILD #1 CHILD #2 Possible Traits Father s Mother s Child s Genotype Father s Mother s Child s Genotype Face Cleft in Chin Hair Widow s Peak Spacing of Eyes Eyes Position of Eyes eyes Length of Eyelashes Eyebrows Position of Eyebrows Nose Lips Mouth Ears Freckles Dimples Hair Color Eye Color Skin Color

5 Human Variations Trait Dominant (both heads) Trait Dominant (both heads) Hybrid (one head, one tail) Recessive (both tails) Eyebrows Hybrid (one head, one tail) Recessive (both tails) Bushy (BB) Bushy (Bb) Thin (bb) Face Cleft in Chin Round (RR) Round (Rr) Square (rr) Position of Eyebrows Nose Not connected (NN) Not connected (Nn) Connected (nn) Hair Absent (CC) Absent (Cc) Present (cc) Lips Large (NN) Medium (Nn) Small (nn) Widow s Peak Spacing of Eyes Curly (HH) Wavy (Hh) Straight (hh) Present (WW) Present (Ww) Absent (ww) Close (EE) Normal (Ee) Far (ee) Eyes Almond (AA) Almond (AA) Round (aa) Mouth Ears Hairy Ears Thick (TT) Medium (Tt) Thin (tt) Large (LL) Medium (Ll) Small (ll) Large (LL) Medium (Ll) Small (ll) Position of Eyes Straight (SS) Straight (Ss) Slant (ss) eyes Large (LL) Medium (Ll) Small (ll) Dimples Hapsburg Lip Absent (HH) Absent (Hh) Present (hh) Present (DD) Present (Dd) Absent (dd) Length of Eyelashes Long (LL) Long (Ll) Short (ll) Freckles Protruding (HH) Slight (Hh) Absent (hh) Present (FF) Present (Ff) Absent (ff)

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