Identifying Mitochondrial Inheritance in a Budding Saccharomyces

Cerevisiae Cells Lacking (Serine/Threonine Phosphatse) PTC1


Satanya McLaughlin

Bayside High School, Queens


Summer Research Program for Science Teachers

August 2007


Course:  Living Environment (New York State Regents Curriculum)/Biology)

Grade: 9th/ 10th    (may also be adapted for A.P. Biology 11th and 12th grade)  

Unit: Molecular Biology or Cell    

Estimated Time Required: Two-class period of 40 minutes or one and half hour (depending upon time constraint, it may take longer or a shorter amount of time to complete)

Aim: How is mitochondrial DNA inherited in a budding yeast cell?

Student Learning Objective:


Introduction: Due to significant advancement in biotechnology a more in depth understanding can be obtained by students, regarding the mechanism of mitochondrial inheritance, by analyzing images of budding yeast cell through microscopy. The relevance of this activity will provide hands-on learning experience for students to acquire an essential skill component of research that is done on a daily basis by various scientists, in order to make major contributions to society that will positively impact the environment, medicine and people, etc.

Recommendation for this lesson to be effective: Lesson should be implemented after students have learned about, cells (structure, size & function), asexual reproduction, cell respiration, genetics and perhaps background information on fluoroscent microscopy (usage and imagery capabilities).


Materials Required:



Lesson Instruction:


1)      Elicit responses- 1) Why is mitochondria important? 2) What controls the mitochondrial inheritance in a budding yeast cell? 3) Why would one want to examine mitochondrial motility in yeast cells? 4) How can one obtain images of a mitochondrial inheritance in a yeast cell?


2)      Discuss students’ responses to previously asked questions and try to direct their responses toward the biological activities mitochondria plays within a cell, while emphasizing the importance of inheritance occurring during the initial stages of the cell cycle (G1/S-phase).


3)      Handout images of BY-474/PTC1 (wild type & mutant strain yeast cell) and have students observe what is taking place in each picture and write their responses of their observations. Make sure that their observations should include, but not limited to, an identification of the differences observed between the BY-474/PTC1 (wild type and mutant cell).  Then have students make a prediction to explain the variation observed between the BY-474/PTC1 (wild type and mutant strain). (Hint: Responses should be aligned with mitochondrial inheritance of retention in the bud tip, but not limited to)


4)   Demonstrate the measuring technique used for quantifying mitochondrial inheritance in small budded cells (< than1/3 of the mother cells) and big budded cells (>1/3 of mother cell) using an overhead projector with a transparency of each image, wild type & mutant, for small and big budded cells. Use a ruler to measure the volume of DNA in the small and large budded cell by drawing a line from the bud neck to the distal tip where mitochondria is visible.  If you have advance computer skills you can use the arrows to draw a line from the top of the bud membrane to the base, and do the same for the mother cell. (Hint: Mitochondria is visible based on the accumulation at the tip of the cell. Follow the image of the cell cycle below)



5)      Handout images provided for students to work in groups of two. Tell the class that they are to design a data table to record the information they are going to gather, which will be based on cell morphology, volume of mitochondria and ratio for BY-474/PTC (wild type & mutant strain). Then assign a given time period to complete this task, 15-20 minutes depending upon availability of time and the amount of images students are given to analyzed. Also handout the guided questions along with the image analysis activity. 


6)      After collecting data students should try link prior observations to data collected and make an inference of what is occurring based on supported evidence of their own data. Also students should pose questions that could possible derive a solution to the problem.



7)      A conclusion should be made based on analysis of data and prior knowledge of scientific concepts. Infer an experimental protocol that can be used to solve the problems encountered from their own analysis.


8)   Evaluation of student comprehension should follow-up on an extension of this lesson by having them conduct an on-line research of literature that can support their conclusion.


Guided Questions:


Use the questions aligned with image analysis activity.


  1. Which cell from fig.1.1 (BY4741) has the greatest volume of mitochondria?



  1. Which cell from fig. 1.1 (BY4741) has the least amount of mitochondria volume?



  1. Based on your previous response, infer why your chosen cell has the most/least volume.







  1. From fig. 1.2 (BY 4741), which cell has the greatest volume of mitochondria?



  1. From fig. 1.2 (BY4741), which cell has the least volume of mitochondria?



  1. Based on your previous response, infer why your chosen cell has the most/least volume.







  1. Which morphology has a greater volume of mitochondria in its bud for the wild type? Why?



  1. From fig. 2.1(ptc1), which cell has the greatest volume of mitochondria?




  1. From fig. 2.2 (ptc1), which cell has the least volume of mitochondria?




  1. Based on your prior responses of questions 8 & 9, infer why your chosen cell has the least/most volume of mitochondria.




   11.  Which morphology has a greater amount of mitochondria in the mutant cell bud tip? Why?






    12.  Which cell has more mitochondria in its bud tip, BY 4741/ptc1? Why?





    13.   What might be the cause for one cell (wild type/mutant) to have more mitochondria in its bud tip compared to the other cell?





    14.  Make some predictions on why there is more volume of mitochondria in the bud tip of the wild type/mutant cell.




N.Y.S. Math, Science and Technology Learning Standards used by this lesson: