You are studying meiosis in an organism where 2n= 28. How many chromosomes will be present in each cell after meiosis I is complete but before meiosis II begins?

Question

A.  7
B.  14
C.  28
D.  56

Clarify Question
 · What is the key concept addressed by the question?
· What type of thinking is required?
· What key words does the question contain and what do they mean?

  Gather Content
  · What do you know about meiosis? How does it relate to the question?

  Consider Possibilities  
  · What other information is related to the question? Which information is most useful?

  Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?  

  Reflect on Process
  · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?


Answer 1

B.  14

Clarify Question
  · What is the key concept addressed by the question?
        o The question asks about the number of chromosomes present after meiosis I.
· What type of thinking is required?
        o You are being asked to apply your knowledge of meiosis to calculate how many chromosomes will be in a cell after meiosis I.
· What key words does the question contain and what do they mean?
        o An organism where 2n=28.  This means that the haploid cells formed after meiosis will have 14 chromosomes.
        o After meiosis I – in meiosis I the chromosome pairs line up on the equator and separate.
        o Before meiosis II – in meiosis II the sister chromatids separate.

  Gather Content
  · What do you know about meiosis? How does it relate to the question?
        o In meiosis there are two stages, in meiosis I the chromosome pairs line up on the equator and separate.  Then in meiosis II the sister chromatids separate.

  Consider Possibilities  
  · What other information is related to the question? Which information is most useful?
        o If the 2n=28 in a cell, then the only two possible answers are n-14 or 2n=28 for haploid or diploid cells respectively.  If a cell had 7 chromosomes that would be less than half the chromosomes of a haploid cell.  If a cell had 56 chromosomes the cell would be tetraploid.

  Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?  
        o If a cell going into meiosis has 28 chromosomes, these will form 14 pairs that line up during meiosis I and separate, forming two cells each with 14 chromosomes.  After meiosis II the sister chromatids would separate forming four cells that are each haploid.

  Reflect on Process
  · Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o This question asked you to apply your understanding of meiosis to predict how many chromosomes would be in a cell after meiosis I. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall that the chromosome pairs separate during meiosis I?  Did you think that the chromosome with two sister chromatids was actually two separate chromosomes?