Table 1: Number of cells observed in each stage of the cell cycle(2 pts)


Predicted %

Number of cells in stage

Total number
of cells counted*

Calculated %


























NOTE: You do not have to draw the cells in each of the stages.





Questions (6 pts)


  1. What stage of the cell cycle (not just mitosis) were most of the onion root tip cells in? Does this make sense? Why? Cite source(s) used.

  2. What is the function of mitosis in a cell that is about to divide? Cite source(s) used.



  1. How accurate were your time predictions, based on your data, for each stage of the cell cycle?




Lab 12 Experiment 1: Meiosis


Read through the Lab 12 Introduction material and the instructions for the Lab 12 Experiment 1. Pay attention to the added information under the Week 4 Experiment link regarding these experiments! In the table below, describe the major events that take place in each stage of Meiosis and indicate the number of chromosomes in each. Cite your sources!(14pts)




Major Events

#  of Chromosomes in each cell

Meiosis I


Prophase I

Nuclear membrane breaks down and chromosomes condense. Two sets of homologous chromosomes are attached at the centromere. Crossing over will occur between the homologous pairs.


Metaphase I





Anaphase I





Telophase I





Meiosis II


Prophase II





Metaphase II





Anaphase II





Telophase II






Sources used:




Questions(12 pts)


  1. Name at least two differences between Meiosis I and Meiosis II in terms of what is produced and what occurs with the chromosomes. Cite source(s) used.

  2. Name and briefly describe two processes that occur during meiosis that contribute to genetic variation. Cite source(s) used.

  3. At the beginning of meiosis I are the cells diploid or haploid? 

What are they at the beginning of meiosis II?

  1. Why is it necessary to reduce the chromosome number of gametes (egg and sperm), but not other cells of an organism? Cite source(s) used.

  2. If humans have 46 chromosomes in each of their body cells, determine how many chromosomes you would expect to find in the following cells:


Sperm _______________      

Egg _________________

Daughter cell from mitosis __________       

Daughter cell from Meiosis II __________


  1. Investigate one of the diseasesfrom the following list.Include the following:
  • Name of the disease or disorder
  • What is the type of mutation and when might it occur?
  • What chromosome is affected?
  • What are the consequences?
  • What is the incidence rate of this disease or disorder?


Down Syndrome          Turner Syndrome                    Klinefelter Syndrome             

Jacobs Syndrome        Triple X                                    Edward Syndrome

Patau Syndrome          Hemophilia                             Cri-du-chat Syndrome

Cystic fibrosis              Prader-Willis Syndrome          Fragile X


Remember to properly cite your sources! (Minimum of 250 words) (6 pt)