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.

Trait	Dominant phenotype	Recessive Phenotype
Flower color	Purple flowers	White flowers
Plant Height	Tall plants	Short Plants
Seed Shape	Smooth seeds	Wrinkled seeds
Seed Color	Yellow seeds	Green seeds

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).   

Trait	Dominant genotype(s)	Recessive genotype(s)
Flower color	Purple =	White =
Plant Height	Tall =	Short =
Seed Shape	Smooth =	Wrinkled =
Seed Color	Yellow =	Green

 

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.

 

Cross Number	Male parent traits	Female parent traits
0	Heterozygous for flower color Heterozygous for height	Homozygous dominant for flower color Heterozygous for height
1	Heterozygous for flower color Homozygous dominant for height	Heterozygous for flower color Homozygous dominant for height
2	Heterozygous for flower color Heterozygous for seed color	Heterozygous for flower color Heterozygous for seed color
3	Homozygous recessive for flower color Heterozygous for seed color	Homozygous dominant for flower color Heterozygous for seed color
4	Homozygous recessive for seed shape Homozygous recessive for height	Heterozygous for seed shape Heterozygous for height
5	Heterozygous for seed shape Heterozygous for height	Heterozygous for seed shape Homozygous recessive for height
6	Homozygous dominant for flower color Homozygous recessive for seed shape	Homozygous recessive for flower color Homozygous dominant for seed shape
7	Heterozygous for flower color Homozygous recessive for seed shape	Heterozygous for flower color Homozygous recessive for seed shape
8	Heterozygous for seed shape Heterozygous for seed color	Homozygous recessive for seed shape Homozygous dominant for seed color
9	Heterozygous for seed shape Homozygous recessive for seed color	Homozygous recessive for seed shape Homozygous recessive for seed color

 

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.

 

Sex	Genotype	Phenotype
Male
Female

 

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.

 

Sex	Gamete 1	Gamete 2	Gamete 3	Gamete 4
Male
Female

 

Step 2: Fill in the Punnett Square below

Male gametes  place across   à Female Gametes: Place below:   ?

 

Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page. 

Phenotype you’ve found in offspring	Number of offspring with this phenotype

 

 

Cross 2:  Please write the number of the cross you are performing:    ______________

Then fill in the genotype and phenotype for each parent below. 

 

Sex	Genotype	Phenotype
Male
Female

 

Step 1:  Determine the different gamete combinations that each parent can contribute to the offspring. 

Sex	Gamete 1	Gamete 2	Gamete 3	Gamete 4
Male
Female

 

Step 2: Fill in the Punnett Square below

Male gametes  place across   à Female Gametes: Place below:   ?

 

Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page. 

Phenotype you’ve found in offspring	Number of offspring with this phenotype

 

Cross 3:  Please write the number of the cross you are performing:    ______________

Then fill in the genotype and phenotype for each parent below. 

 

Sex	Genotype	Phenotype
Male
Female

 

Step 1:  Determine the different gamete combinations that each parent can contribute to the offspring. 

Sex	Gamete 1	Gamete 2	Gamete 3	Gamete 4
Male
Female

 

Step 2: Fill in the Punnett Square below

Male gametes  place across   à Female Gametes: Place below:   ?

 

Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page. 

Phenotype you’ve found in offspring	Number of offspring with this phenotype

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.