Meiosis results in a reassortment of maternal chromosomes (inherited from the mother) and paternal chromosomes (inherited from the father). If n=4 for a given species, and ignoring the effects of crossing over, what is the probability that a gamete will receive only paternal chromosomes?

Question

A.  1/2
B.  1/4
C.  1/8
D.  1/16

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 independent assortment? 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

D.  1/16

Clarify Question
  · What is the key concept addressed by the question?
        o The question asks about the probabilities in independent assortment.
· What type of thinking is required?
        o You are being asked to apply your knowledge of independent assortment to calculate the probability of all chromosomes in a gamete coming from one parent.
· What key words does the question contain and what do they mean?
        o Probability that a gamete will receive only paternal chromosomes – by independent assortment, chromosomes align independently. The probability that four chromosomes all align together will be the product of each probability individually.

  Gather Content
  · What do you know about independent assortment? How does it relate to the question?
        o For each chromosome pair lining up during metaphase I of meiosis there is a 50:50 probability for it to move into one new cell or the other.

  Consider Possibilities     · What other information is related to the question? Which information is most useful?
        o The probability of independent assortment is like flipping a coin.  If the odds of a head is 50% or ½, then the probability of two heads is ½ x ½ or ¼.  .

  Choose Answer
  · Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?  
        o Following the coin tossing analogy.  If a cell has 4 chromosomes that segregate independently the probability that the chromosomes from the father would all move to one cell is ½ x ½ x ½ x ½ = 1/16.

  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 independent assortment. 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 probability of two chromosomes segregate together is the probability of each event separately multiplied?  Did you think that the probabilities would be added?