Biology

Read Chapter 7 and print out the sample genetic cross 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

 

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 an allele?  Give an example of 2 alleles of any gene.  (0.5 pts)

 

An allele is a trait of the gene. Individuals has two copies of each gene inherent from both parents.  Example of 2 alleles for a gene could be the blood type or eye color

 

b) What is the difference between an organism that is a homozygote and one that is a heterozygote?  (0.25 pts)

 

Homozygote individual inherits the same two alleles for this gene, and Heterozygote individual inherits different alleles from each parent.

 

 

c) What is the difference between an organism’s genotype and its phenotype? (0.25 pts)

The Phenotype is the outward appearance of an individual, and  the Genotype is the organism’s genetic composition.

 

 

2.) For each trait indicate the genotypes that are possible.  Use the first letter of the dominant trait to indicate the trait.   (2pts)

 

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 student 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

Homozygous dominant for height

Heterozygous for flower color

Homozygous dominant for height

1 Heterozygous for flower color

Heterozygous for height

Homozygous dominant for flower color

Heterozygous for height

2 Heterozgyous for flower color

Heterozygous for seed color

Heterozgyous 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

Homozygous recessive for seed color

Homozygous recessive for seed shape

Homozygous recessive for seed color

9 Heterozygous for seed shape

Heterozygous for seed color

Homozygous recessive for seed shape

Homozygous dominant for seed color

 

Now you can use the charts and Punnett squares on each of the following pages to complete your 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 problem 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?  (1pt)

2. A) Can two tall and smooth seeded parents produce offspring that are short and have wrinkled seeds?   (To receive a full credit for this assignment you MUST explain your answers for part A and part B by drawing the respective Punnett squares for each of your answers).

Explain using a Punnett square why you think this outcome is possible or not.  (1pt)

 

B) Can two white flowered and green seeded parents produce offspring that have Purple flowers and have yellow seeds?

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