CPO Science Link Teacher's Guide

A3 Crazy Traits

Crazy Traits

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A3 Crazy Traits

What role does probability play in heredity?

NASA has found a rst generation of Crazy Creatures on Geneticus that all

have the same combination of alleles—one dominant allele and one recessive

allele—for all their traits. Since all the parents have the same alleles, many have

incorrectly assumed that future generations will look exactly like their parents.

You know that this isn’t the case! It is true that in sexual reproduction, for each

gene, you get at least one allele from your mother and one from your father.

However, the alleles you inherit are determined by two factors: (1) the alleles that

your parents have; and (2) the alleles you inherit from each parent. The alleles

you inherit from each parent are determined by chance, or probability. In this

investigation, you will do an activity that demonstrates how probability can help

predict the appearance of Crazy Creature offspring.



Determining the genotype

1. The first trait you will flip a coin for is sex. Choose the male sex chromosome coin (X on one side and Y

on the other) and the female sex chromosome coin (X on both sides). Shake and flip both coins onto the

table. Record the allele from each parent and genotype in columns 2, 3, and 4 of the first row of Table 1.

2. For each of the other traits, you will flip coins to see what allele your creature inherits from each parent.

This will determine the creature’s genotype and phenotype. An organism’s genotype is the set of alleles

of a gene it contains. An organism’s phenotype is the form of a trait that it displays. In this activity, both

parents have the same genotype (and, therefore, phenotype) for all traits (Tt) since they are from that

isolated population on Geneticus. You will need the blue (egg) coin with a capital T on one side and a

lower case t on the other side. You will also need the green (sperm) coin with a capital T on one side and

a lower case t on the other side.

3. Flip the coins for the next trait – skin color. The side that lands up on each coin represents the sperm and

egg that unite during fertilization. Record your results in Table 1.

4. Repeat this procedure for traits 3 through 14.

Materials:

✔ Crazy Traits set

Name ____________________________________________ Date ________________________

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INVESTIGATION

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A3 Crazy Traits

Crazy Traits

Table 1: Genotypes and phenotypes of offspring

Trait Allele from mother Allele from father Genotype Phenotype

1. Sex

2. Skin color

3. Leg

4. Foot

5. Arms

6. Hands

7. Eye color

8. Eyebrows

9. Beak

10. Ears

11. Antenna length

12. Antenna shape

13. Tail

14. Wings

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A3 Crazy Traits

Crazy Traits

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Table 2: Key to genotypes and phenotypes

Trait Genotypes and phenotypes

1. Sex

XX – female XY – male

2. Skin color

TT – red Tt – purple tt – blue

3. Leg

TT – short Tt – short tt – long

4. Foot

TT – webbed Tt – webbed tt – talon

5. Arms

TT – long Tt – long tt – short

6. Hands

TT – paws Tt – paws tt – claws

7. Eye color

TT – red Tt – one red and one green tt - green

8. Eyebrows

TT – unibrow Tt – unibrow tt – separate

9. Beak

TT – trumpet Tt – trumpet tt – crusher

10. Ears

TT – elephant Tt – elephant tt – mouse

11. Antenna length

TT – long Tt – long tt – short

12. Antenna shape

TT – knob Tt – knob tt – star

13. Tail

TT – long Tt – short tt – none

14. Wings

TT – no wings Tt – no wings tt – wings

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INVESTIGATION

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A3 Crazy Traits

Crazy Traits



Stop and think

a. What information do the letters on the sperm and egg coins indicate: alleles, genotype, or phenotype?

b. For the sperm coin, what is the probability of getting a T or a t? State your answer as a fraction and a

percent.

c. For the egg coin, what are the chances of getting a T or a t? State your answer as a fraction and a percent.

d. When both coins are ipped at once, what are your chances of getting each of the following

combinations: TT, Tt, or tt? State your answer for each as a fraction and a percent.



Building your creature

1. Once you have completed columns 2 through 4 of Table 1, use Table 2 to look up the phenotype for each

trait. Record the phenotype for each trait in column 5 of Table 1.

2. Once you have completed Table 1, select the correct body parts to build your creature.

3. Orient the body for either male (round end down) or female (round end up).

4. Carefully assemble your creature.

5. Give your creature a name and make it a name tag.

6. Display your creature in the area designated by your teacher.

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A3 Crazy Traits

Crazy Traits

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

Analyzing the results

a. Examine the creatures. Do any of them look exactly alike? Do any of them look exactly like their

parents? Why or why not?

b. How does this investigation explain why offspring may resemble their parents, but never look exactly like

them?

c. How does this investigation explain why, in sexual reproduction, siblings may resemble each other, but

never look exactly alike (unless they are identical twins)?

d. Count the number of males and number of females. Does the number of each match the chances of

getting a male or female in the game? Why or why not?

e. Explain to the NASA scientists why the offspring of this isolated generation of Tt Crazy Creatures may

end up looking quite different from their parents.

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A3 Crazy Traits

Crazy Traits

f. In asexual reproduction, the offspring are identical to the parent organism. The term genetic variation

refers to the variety of alleles of genes in a population. Why does sexual reproduction result in offspring

with genetic variation while asexual reproduction does not?



Exploring on your own

Write about the life of your Crazy Creature. Pretend that it lives somewhere here on Earth. Think about its

traits. What type of habitat is it best suited for? What type of food might it eat? What predators would eat it?

How would it protect itself? Even though you are pretending, describe real habitats, organisms, and conditions

that exist on Earth.

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