A cell biologist examines a leaf cell from an alfalfa plant during metaphase of mitosis and determines that 32 chromatids are present. The role of fertilization in this species is to (Check all that apply)
_____ Produce a new cell that has a combination of chromosomes from 2 different parents.
_____ Increase the number of chromosomes per cell from 16 to 32.
_____ Increase the number of chromosomes per cell from 8 to 16.
_____ Combine the chromosomes from 2 haploid cells into a single diploid cell.
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 fertilization? 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?
__X__ Produce a new cell that has a combination of chromosomes from 2 different parents.
_____ Increase the number of chromosomes per cell from 16 to 32.
__X__ Increase the number of chromosomes per cell from 8 to 16.
__X__ Combine the chromosomes from 2 haploid cells into a single diploid cell.
Clarify Question
· What is the key concept addressed by the question?
o The question asks about what happens during fertilization.
· What type of thinking is required?
o You are being asked to analyze statements about fertilization to choose which is correct.
· What key words does the question contain and what do they mean?
o 32 chromatids in metaphase of mitosis – after replication of DNA during S phase each chromosome now contains two attached sister chromatids.
Gather Content
· What do you know about fertilization? How does it relate to the question?
o In fertilization two haploid gametes fuse to form a diploid fertilized egg.
o If a cell has 32 chromatids, these chromatids are paired as a chromosome. So the diploid number for this cell will be 16 chromosomes. If this cell goes through meiosis forming haploid gametes, each gamete will have 8 chromosomes
Consider Possibilities · What other information is related to the question? Which information is most useful?
o In fertilization two haploid gametes fuse to form a diploid cell. In this case the haploid gametes each have 8 chromosomes, so they could not fuse to form a cell with 32 chromosomes.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o In fertilization two haploid gametes fuse to form a diploid cell. In this case the haploid gametes each have 8 chromosomes, so they would fuse to form a cell with 16 chromosomes.
o Because these gametes contain chromosomes from two different individuals, the chromosomes in the fertilized cell will be a combination of those from the two different parents.
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 statements about fertilization to explain properties of the cell that is formed. If you got the correct answer, great job! If you got an incorrect answer, where did the process break down? Did you recall that if a cell has 32 chromatids its diploid number is 16 chromosomes? Could you calculate that the haploid gametes would have half the number of chromosomes or 8? Did you understand that during fertilization two haploid gametes fuse to form a diploid cell containing 16 chromosomes that would be combined from two different parents?
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