STUDENT LABORATORY PACKET

Transcription

1 L13a Mendelian Genetics- Corn Page 1 of 6 STUDENT LABORATORY PACKET Student s Full Name Lab #13a: Mendelian Genetics in Corn Lab Instructor Date Points Objectives: Students will be able to: Observe the patterns of Mendelian inheritance in corn. Calculate the expected (predicted) phenotype and ratios for a monohybrid cross. Determine the actual phenotype ratios for a monohybrid cross. Background: Read Dragonfly pp PRE-LAB: (Do Before Coming to Lab) Each kernel on an ear of corn represents one offspring that resulted from sexual reproduction (the combination of sperm and egg nuclei). One gene is responsible for kernel color. The dominant allele P is responsible for a dark kernel, while the recessive p allele is responsible for a kernel. Complete the Punnett squares and determine the phenotype percentages below: 1. PP x pp 2. PP x Pp 3. Pp x Pp 4. Pp x pp

2 L13a Mendelian Genetics- Corn Page 2 of 6 1. What is the phenotype of a kernel that is PP? 2. What is the phenotype of a kernel that is pp? 3. What is the genotype for a corn plant or kernel that is heterozygous for kernel color?. 4. What is the phenotype for a heterozygote?. 5. How can a ratio of 3:1 be expressed as a fraction?, a percentage? LABORATORY EXERCISE Materials: Genetic ears of corn, pencil, paper, calculator. *Note Do not pick at, puncture, or eat any kernels. A $ replacement fee for damaged corn will be levied to your school account. Procedure: 1. Work in lab groups of four. Your task is to count the number of kernels and the number of kernels that occur in a sample size of 250 kernels on an ear of corn. 2. Student 1 should read aloud one row of kernels at a time, indicating the color ( or ). 3. Student 2 should keep tally of the number of kernels and the number of kernels as student 1 calls out the colors. 4. Student 3 should keep tally of the total number of kernels counted and inform the group when 250 is reached. At this point, you can stop counting. 5. Record your tally below. Kernel Tally All Total: Total: Total: Record the total number of and kernels in the data table on the next page in the Group Data column. 7. Calculate and record the percentages of and kernels (round to the nearest 0.1). For instance: Number of (color) kernels / 250 * 100 = % 8. Record your group data on the blackboard. When all lab groups have reported, record the class totals and calculate the percentages on the data table.

3 L13a Mendelian Genetics- Corn Page 3 of 6 Data Table: Kernels Group Data Class Data Number % Number % Kernels Total % 100% 9. From your group data only, determine the genotypes of the parents of your ear of corn. Show the Punnett square for this cross below (*Hint look at the percentages from your data table and compare them to the Punnett squares from the pre-lab to help you determine the genotype of the parents). x Analysis of Data: Record and calculate the following: % Difference between observed and expected = [ Observed Expected ] / Expected * 100 Data Table: Expected Number (from Punnett square) Observed Number (from Data collected) [ Observed Expected] % Difference between observed and expected Group Class Group Class

4 L13a Mendelian Genetics- Corn Page 4 of 6 Conclusions: 1. Compare your group and class percent differences. Which set of data comes closest to the expected ratio? 2. Mendel counted thousands of pea plants for each cross in his experiments before reaching his conclusions. a. Why did he need to count so many? b. Which data set, group or class, is more valid. Why? 3. If all the offspring of a cross between a parent and a parent are, then what are the genotypes of the parents? and. Show the Punnet square below. 4. Each kernel you counted in this lab is an offspring resulting from sexual reproduction. Name three processes that contribute to variation in sexual reproduction. *Note Copy your observations and conclusions onto the Student Answer Packet. Only the answer packet will be collected and graded. You will need the Student Lab Packet for your records, and to study from for quizzes.

5 L13a Mendelian Genetics- Corn Page 5 of 6 STUDENT ANSWER PACKET Student s Full Name Lab #13a: Mendelian Genetics in Corn Lab Instructor Date Points Pre-Lab FINAL GRADE Max. value 1pt. pt. Procedure/Observations: Corn Kernels: Kernels Max. value 5 pts. pts. Group Data Class Data Number % Number % Kernels Total % 100% Punnet Square: x

6 L13a Mendelian Genetics- Corn Page 6 of 6 Data Table: Expected Number (from Punnett square) Observed Number (from Data collected) [Expected -Observed] % Difference between observed and expected Group Class Group Class Max. value 4 pts. pts. Analysis/Conclusions: 1. Compare your group and class percent differences. Which set of data comes closest to the expected ratio? 2. Mendel counted thousands of pea plants for each cross in his experiments before reaching his conclusions. a. Why did he need to count so many? b. Which data set, group or class, is more valid. Why? 3. If all the offspring of a cross between a parent and a parent are, then what are the genotypes of the parents? and. Show the Punnet square below. 4. Each kernel you counted in this lab is an offspring resulting from sexual reproduction. Name three processes that contribute to variation in sexual reproduction.