Read Chapter 7 and print out the sample genetic cross posted below the lab on launchpad to use as a guide.
Below is a list of the phenotypes used in this lab. These are all single gene traits that show complete dominance. Use this information to set up and analyze your crosses.
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Trait
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Dominant phenotype
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Recessive Phenotype
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Flower color
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Purple flowers
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White flowers
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Plant Height
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Tall plants
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Short Plants
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Seed Shape
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Smooth seeds
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Wrinkled seeds
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Seed Color
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Yellow seeds
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Green seeds
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Part I: Symbols and definitions:
1. a) What is a gene? What is an allele? Give an example of 2 alleles of a human gene.
b) What is the difference between an organism that is a homozygote and one that is a heterozygote?
c) What is the difference between an organism's genotype and its phenotype?
2. For each trait in the table below, indicate ALL OF THE GENOTYPES that are possible. Use the first letter of the dominant trait to indicate the trait (for example, use the letter P for purple).
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Trait
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Dominant genotype(s)
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Recessive genotype(s)
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Flower color
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Purple =
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White =
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Plant Height
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Tall =
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Short =
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Seed Shape
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Smooth =
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Wrinkled =
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Seed Color
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Yellow =
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Green
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Pick three of the crosses to complete using any 3 of the last 4 digits of your CUNYFirst BC student Empl ID. If there are repeats, pick random numbers, so you are doing 3 different crosses. Circle the numbers of the crosses you are doing in column 1 below.
You must pick 3 different crosses. If there are multiple repeated numbers in your ID, pick additional numbers of your choice.
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Cross Number
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Male parent traits
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Female parent traits
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0
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Heterozygous for flower color
Heterozygous for height
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Homozygous dominant for flower color
Heterozygous for height
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1
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Heterozygous for flower color
Homozygous dominant for height
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Heterozygous for flower color
Homozygous dominant for height
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2
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Heterozygous for flower color
Heterozygous for seed color
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Heterozygous for flower color
Heterozygous for seed color
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3
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Homozygous recessive for flower color
Heterozygous for seed color
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Homozygous dominant for flower color
Heterozygous for seed color
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4
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Homozygous recessive for seed shape
Homozygous recessive for height
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Heterozygous for seed shape
Heterozygous for height
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5
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Heterozygous for seed shape
Heterozygous for height
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Heterozygous for seed shape
Homozygous recessive for height
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6
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Homozygous dominant for flower color
Homozygous recessive for seed shape
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Homozygous recessive for flower color
Homozygous dominant for seed shape
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7
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Heterozygous for flower color
Homozygous recessive for seed shape
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Heterozygous for flower color
Homozygous recessive for seed shape
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8
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Heterozygous for seed shape
Heterozygous for seed color
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Homozygous recessive for seed shape
Homozygous dominant for seed color
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9
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Heterozygous for seed shape
Homozygous recessive for seed color
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Homozygous recessive for seed shape
Homozygous recessive for seed color
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Now you can use the charts and Punnett squares on each of the following pages to complete your crosses. Use the sample of a genetic cross posted on Launchpad directly below the lab for a guide in doing these crosses.
Cross 1: Please write the number of the cross you are performing: ______________
Then fill in the genotype and phenotype for each parent below. Use the sample of a genetic cross posted on launchpad directly below the lab for a guide.
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Sex
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Genotype
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Phenotype
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Male
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Female
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Step 1: Determine the different gamete combinations that each parent can contribute to the offspring. Check the hint from the sample problem when you are doing this.
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Sex
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Gamete 1
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Gamete 2
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Gamete 3
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Gamete 4
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Male
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Female
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Step 2: Fill in the Punnett Square below
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Male gametes place across à
Female Gametes:
Place below: ↓
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Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page.
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Phenotype you've found in offspring
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Number of offspring with this phenotype
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Cross 2: Please write the number of the cross you are performing: ______________
Then fill in the genotype and phenotype for each parent below.
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Sex
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Genotype
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Phenotype
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Male
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Female
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Step 1: Determine the different gamete combinations that each parent can contribute to the offspring.
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Sex
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Gamete 1
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Gamete 2
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Gamete 3
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Gamete 4
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Male
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Female
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Step 2: Fill in the Punnett Square below
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Male gametes place across à
Female Gametes:
Place below: ↓
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Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page.
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Phenotype you've found in offspring
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Number of offspring with this phenotype
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Cross 3: Please write the number of the cross you are performing: ______________
Then fill in the genotype and phenotype for each parent below.
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Sex
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Genotype
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Phenotype
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Male
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Female
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Step 1: Determine the different gamete combinations that each parent can contribute to the offspring.
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Sex
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Gamete 1
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Gamete 2
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Gamete 3
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Gamete 4
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Male
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Female
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Step 2: Fill in the Punnett Square below
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Male gametes place across à
Female Gametes:
Place below: ↓
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Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page.
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Phenotype you've found in offspring
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Number of offspring with this phenotype
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Questions:
1. Are gametes haploid or diploid? What about the offspring, are they haploid or diploid?
2. a) Can two white flowered wrinkled seeded parents produce offspring that have purple flowers and smooth seeds?
Explain using a Punnett square why you think this outcome is possible or not.
b) Can two purple flowered and yellow seeded parents produce offspring that have white flowers and green seeds?
Explain using a Punnett square why you think this outcome is possible or not.