Week 5 life science

Week 5 Midweek Assignment: Monsters Genetic Lab

Predicting Genotype and Phenotype and Using Punnett Squares

Background

Punnett squares are used to predict the genotypes and phenotypes of offspring from a parent cross. Genotypes represent the alleles (the actual genetic makeup), and phenotypes are the expression of the alleles (the appearance). There are several types of inheritance patterns, but this activity focuses on three. Complete dominance is the inheritance pattern which results in the expression of the dominant phenotype as long as one dominant allele is present. For example, if tall (T) plants are dominant to short (t) plants, the TT genotype and the Tt genotype both result in tall plants. The tt genotype would result in short plants. Most genes follow this pattern. Incomplete dominance results in a phenotype that is intermediate between the dominant and recessive phenotype when an individual is heterozygous. For example, in snapdragons, red (R) flowers have incomplete dominance over white (R’) flowers. A genotype of RR results in red flower, R’R’ results in white flowers, and RR’ (heterozygous) results in pink flowers. Codominance allows expression of both alleles. For example, in blood type, A and B are codominant to O. An individual with one A allele and one B allele has AB blood type because neither allele is dominant over the other. They are both expressed.

Procedure

There are three parts to this lab. Follow the directions carefully for each part, filling in the data tables as you work through each section.

In Part One, you use a coin to determine the genotype for the female monster. In Part Two, you determine the genotype or phenotype for the traits of the male monster. Finally, in Part Three, you cross your female and male monsters to produce offspring and use Punnett squares to determine their traits.

Part One

1. Flip a coin twice to determine the genotype for each trait and record it in the data table on the next page.

a. Heads = allele 1, Tails = allele 2

b. ( Example: if you flipped heads twice, your monster would have two copies of allele 1 for his genotype. Look ahead to Table 2 to see what a partially filled out table looks like. )

2. Determine the phenotype resulting from the allele pair for each trait.

3. Repeat steps 1‐2 for each trait and complete Table 1 for female monster.

Table 1: Genotypes & Phenotypes for Female Monster

Trait	Allele 1	Allele 2	Genotype	Phenotype
Eye	Two small eyes (E)	One large eye (e)
Eye Color (incomplete)	Red (R)	White (R’)
Skin Color (codominant)	Green (G)	Blue (B)
Tail Shape	Curly (C)	Straight (c)
Tail Color	Purple (P)	Orange (p)
Teeth	Sharp (S)	Round (s)
Feet (incomplete)	Four toes (F)	Two toes (F’)
Horn Color	Purple (W)	White (w)
Ear shape	Pointy (Y)	Round (y)
Claws	Long (L)	Short (l)

Part Two

Fill in the missing genetic information in the table for the male based on the alleles used for the traits as found in Table 1.

Table 2: Genotypes & Phenotypes for Male Monster

Trait	Genotype	Phenotype
Eyes	ee
Eye Color (incomplete)		White
Skin Color (codominant)		Green
Tail Shape		Straight
Tail Color	Pp
Teeth		Round
Feet (incomplete)	FF’
Horn Color	ww
Ear shape	yy
Claws		Short

Part Three

The female monster (described in Table 1) and the male monster (described in Table 2) plan to have baby monsters. They are interested in finding out the probability that their offspring will have each trait by using Punnett squares.

Here is a YouTube video that explains Punnett squares and how they are used to predict the outcomes of genetic crosses. Monohybrids and the Punnett Square Guinea Pigs (06:27)

Example: based on the video.

Hairiness	Hairy Guinea Pig
	H	h
Hairless Guinea Pig	h	Hh	hh
	h	Hh	hh

In this case, there is a 50% chance of having a hairy guinea pig for the offspring since two of the four squares would have the hairy phenotype. (1 square would be 25%, 2 squares 50%, 3 squares 75%, and 4 squares 100%)

Fill in the Punnett squares to predict what traits would result from a cross between the two monsters for each trait and answer the questions.

1. Eyes – What percent of offspring will have only one eye?

EYES	Male Genotype
Female Genotype

2. Eye Color – What percent of offspring will have red eyes?

EYE COLOR	Male Genotype
Female Genotype

3. Skin Color – What percent of offspring will have green skin?

SKIN COLOR	Male Genotype
Female Genotype

4. Tail – What percent of offspring will have a tail?

TAIL	Male Genotype
Female Genotype

5. Feet – What percent of offspring will have three toes?

FEET	Male Genotype
Female Genotype

6. Horn Color – What percent of offspring will have purple horns?

HORN COLOR	Male Genotype
Female Genotype

7. Ears – What percent of offspring will have ears?

EARS	Male Genotype
Female Genotype

8. Claws – What percent of offspring will have long claws?

CLAWS	Male Genotype
Female Genotype

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