Chapter 10 Notes Pt. 2 The division of nuclear material in which each new nucleus obtains the same number of chromosomes and the same nuclear code as the original nucleus is call mitosis. Mitosis occurs in four phases. Interphase occurs between mitosis. Interphase: Cell contains easily seen nucleus and nucleolus- chromosomes appear as fine dots within nucleus Mitosis: 4 steps Prophase – cell nucleus enlarged –nucleolus no longer visible- chromosomes appear as short strands within nucleus. Metaphase – chromosomes long and thin strands – chromosomes lined up along cell center and look like “spider on a mirror”.
Anaphase – two sets of separate chromosomes can be seen – look as if they are being pulled apart from one another. Telophase – chromosomes appear at opposite ends of cell – middle of cell has line across center that divides it almost into two new cells. Cytokinesis: appear as two daughter cells, small and side by side – then starts in interphase again. Use notes from lecture, pictures on the board, and the description from above to answer the following questions for each phase: Interphase: 1.
Describe the contents of a nucleus during interphase. ____________________________________________ 2. Are a nucleolus and nuclear membrane present in the cell? ________________________________________ 3. Are distinct rod-shaped structures called chromosomes easily observed in the nucleus at this time? ________ 4. Are chromosomes present in cells during interphase? _____________________________________________ 5. What term is used to describe nuclear contents during interphase? __________________________________ 6. What important event occurs to chromosomes during interphase? ___________________________________ 7.
What other important events occur during interphase? ____________________________________________ Prophase: 8. Are chromosomes now visible during prophase? _______________________________________ 9. Describe the changes that have occurred to the nucleolus and nuclear membrane from interphase to prophase. __________________________________________________________________________________________ 10. Explain why chromosomes can now be observed but were not observable during interphase. __________________________________________________________________________________________
Metaphase: 11. Describe where the chromosomes are now located in relation to the cell. ____________________________ 12. Can evidence of chromosome duplication (replication) now be observed? ___________________________ 13. What are the fibers called become visible during this phase? ______________________________________ 14. What term is used to describe the structure at which each fiber attaches to a chromosome? _____________ Anaphase: 15. In metaphase, chromosome pairs were lined up along the cell’s center.
Describe what is occurring to each chromosome pair during anaphase. _____________________________________________________________ 16. Toward what area of the cell are the chromosomes being directed? ____________________________________ 17. What structure is responsible for the movement of chromosomes during this phase? ___________________ Telophase: 18. What cell parts begin to reappear during this phase? ____________________________________________ 19. Describe the location of the chromosomes now compared to where they were during metaphase. _________________________________________________________________________________________ Cytokinesis: 20. How many cells have now formed from an original cell? _________________________________________ 21. Explain how the number of chromosomes found in each daughter cell compares to the number found in the original cell before mitosis. ___________________________________________________________________ Analysis: 1. The term “mitosis” comes from the Greek word meaning “thread”. Explain why this word may be helpful in describing this process of nuclear division. ______________________________________________________ 2. Explain how the process of mitosis helps an organism to grow in size. __________________________________________________________________________________________ __________________________________________________________________________________________ Draw below to show the structures visible during each stage of mitosis. Draw and label the structures listed below. Be sure to label each miotic stage. Interphase: draw and label nuclear membrane, nucleolus, chromatin, centriole.
Prophase: draw and label disappearing nuclear membrane, disappearing nucleolus, original chromosomes (shaded), chromosome copies (unshaded). Metaphase: draw and label two chromosome pairs as they would appear during metaphase. Label chromosomes and spindle fibers. Anaphase: draw and label the two chromosome pairs as they separate in anaphase. Label centromeres. Telophase: draw and label reforming nuclear membrane, reforming nucleolus, pinching in of cell membrane Cytokinesis: draw in and label nucleus, nucleolus, nuclear membrane, and chromatin.
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