is essentialy the same in all animal cells, but depending on the tissue, it take
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is essentialy the same in all animal cells, but depending on the tissue, it takes from 5 minutes to several 3. Arraage the chromosomes as dhey appear in early prophase Name the structure that assembles during this phase. hours to complete. In most cells, centriole replication occurs daring interphase of the next cell cycle At the end of cell division, two daughter cells exist- each with a smaller cytoplasmic mass than the mother cell and carry out the normal spectrum of metabolic processes until it Draw early prophase in the space provided on your Review Sheet (question 11, page 52). but genetically ideatical to it. The daughter cells grow is their turn to divide. Cel division is extremely important during the body's 4 Arrange the chromosomes as they appear in late prophase growth period. Most cells divide until paberty, when nor mal body size is achieved and overall body growth ceases. After this time in life, only certain cells carry out cell divi- sion routinely-for example, cells subjected to abrasion (epithelium of the skin and lining of the gut). Other cell as liver cells-stop dividing but retain this ability should some of them be removed or damaged. Skeletal muscle, cardiac muscle, and most mature neurons almost completely lose this ability to divide and thus are What structure on the chromosome centromere do the growing spindle microtubules attach to? What structure is now present as fragments? tional, in the space providedon your Review Sheet (question 11, page 52) severely handicapped by injary 5. Arrange the chromosomes as they appear in metaphase ACTIVITY What is the name of the imaginary plane that the chromo- somes align along? Draw metaphase in the space provided on your Review Identifying the Mitotic Stages 1. Watch a video presentation of mitosis (if available) 2 Using the three-dimensional models of dividing cells provided, identify each of the mitotic phases described Sheet (question 11, page 52). Arrange the chromosomes as they appear in anaphase. What does untwisting of the chenille sticks represent? (Figure 4.4). 6. Obtain a prepared slide of whitefish blastulas to study the of mitosis. The ceills of each blastula (a stage of em- yonic development consisting of a hollow ball of cells) are imately the same mitotic stage, so it may bé neces- sary to observe more than one blastula to view all the mitotic stages. A good analogy for a blastula is a soccer ball in which each leather piece making up the ball's surface represents an embryonic cell. The exceptionally high rate of mitosis ob- served in this tissue is typical of embryos, but if it occurs in specialized tissues it can indicate cancerous cells, which also the slide Each sister chromatid has now become a Drnw anaphase in the space provided on your Review Sheet (question 11, page 52) Arrange the chromosomes as they appear in telophase. 7. carefully, identifying the four mitotic phases and the process of cytokinesis. Compare your observations with Figure 4.4, Briefly list four reasons why telophase is like the reverse of prophase. and verify your identifications with your instructor. "Chenille Stick Mitosis I. Obtain a total of eight chenille sticks, each measuring 3 inches: four of one color and four of another color (e.g.. four green and four purple). 2. Assemble the chenille sticks into a total of four chro- mosomes (each with two sister chromatids) by twisting two sticks of the same color together at the center with a single Draw telophase in the space provided on Sheet (question 11, page 52) twist. What does the twist at the center represent?Explanation / Answer
2. The twist at the middle represents the centromere which is the most constricted part of the chromosome. It is the region where the two sister chromatids attach to each other.
3. Prophase is the first phase of mitosis. During this phase the nuclear membrane and nucleolus disappear whereas the chromatin coils and folds up into chromosomes. The structure which assembles is the mitotic spindle.
4. The centromere has a protein complex called the kinetochore. This is where the spindle microtubular attach. During this phase the nuclear membrane disrupts and is present as fragments.
5. Metaphase plane is the name given to the equatorial region along which the cells divide. It is perpendicular to the spindle fibres of the cell.
6. The untwisting of the chenille sticks represents the separation of the sister chromatids after which they go to the opposite poles. Each sister chromatid now becomes an independent chromosome.
7. Telophase is known as reverse Prophase because:
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