A cell biologist examines a diploid cell from a particular species of butterfly during prometaphase of mitosis and determines that 10 centromeres are present. Based on this finding, how many chromatids should be present in a single cell from this species in metaphase I of meiosis?
What will be an ideal response?
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 the number of chromatids in a cell? 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?
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Clarify Question
· What is the key concept addressed by the question?
o The question asks about the number of chromatids in a cell during meiosis.
· What type of thinking is required?
o You are being asked to analyze an experiment to predict the number of chromatids present in metaphase I of meiosis.
· What key words does the question contain and what do they mean?
o 10 centromeres are present in prometaphase. This means the cell has a diploid number of 10 chromosomes.
Gather Content
· What do you know about the number of chromatids in a cell? How does it relate to the question?
o Sister chromatids are formed after DNA replicates. Pairs of sister chromatids are chromosomes.
Consider Possibilities
· What other information is related to the question? Which information is most useful?
o In metaphase I of meiosis, pairs of homologous chromosomes pair up, each with two sister chromatids.
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 has 10 centromeres in prometaphase it has 10 chromosomes. The cell is still diploid, so 2n=10. In metaphase I of meiosis there will still be 10 chromosomes. Each chromosome contains two sister chromatids. So there will be 20 chromatids in total.
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 analyze the results of an experiment to calculate how many chromatids are present in metaphase I. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you understand that the cell would still be diploid in metaphase I? Did you realize that each chromosome would have a centromere? Did you understand that each chromosome would have two sister chromatids?
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