Unit A Reproduction

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11. Rotate the high-power lens into place, and locate one cell that is dividing. Determine which stage of mitosis it is in. Copy Table 1 into your notebook to record which of the four mitotic stages the cell is in. Table 1 Percentage of Stage Number of cells cells in stage (%) prophase metaphase anaphase telophase 12. Move your slide, and repeat step 11 until you have recorded information for 20 dividing cells. Make sure that you do not include any cells in interphase. 13. For each stage, use the formula in step 4 to calculate the percentage of cells, and record the values in your table. 14. Repeat steps 9 to 13 using the whitefish embryo slide. 15. Calculate the length of time that cells spend in each stage of mitosis. It usually takes between 12 and 16 hours to complete mitosis. You will use 12 hours to make the calculations easier. To calculate the number of hours spent in each stage, multiply the percentage of cells by 12 hours. For example, suppose that you found 40 % of the 20 cells in metaphase: Time spent in metaphase 40 % 12 h 4.8 h 16. Draw two circles to represent two clocks: one for the onion root tip cells and one for the whitefish embryo cells. 17. Use the data you collected to create clocks that indicate the amount of time spent in each stage of mitosis. Analysis (a) Which areas of the onion root tip have the greatest amount of cell division? (b) Were there any differences in the rates in the three areas of the whitefish embryo? What do you conclude from this? (c) Which has the greater percentage of dividing cells, the onion root tip or the whitefish embryo? (d) Do your results support your hypothesis? (e) Was your prediction correct? Explain. (f) What do your clocks indicate about the time spent in the different stages of mitosis in the plant and the animal cell samples? Evaluation (g) Describe possible sources of error in this investigation. (h) How could you improve the procedure for this investigation? (i) Are there stages missing from your cell clock? If so, identify them. Synthesis (j) What is the benefit of knowing the rate of cell division in various organisms? (k) Describe a different method that you could use to calculate the rate of growth in living things. (l) Although mitosis is divided into stages to make it easier to discuss, the process is continuous. Which of your observations suggest that mitosis is a continuous process? (m) Choose one of the cell division rates you determined in this investigation. Draw a circle graph that shows the percentages of cells dividing and not dividing. (n) Technology allows scientists to count cells much faster than you did in this investigation. Suggest a method for counting cells using technology. LEARNING TIP A clock is a type of circle (or pie) graph. Refer to the Skills Handbook for help constructing a circle graph. NEL Chapter 2 Investigation 67
CHAPTER 2 Review Cell Growth and Reproduction Key Ideas The functions of cell division are growth, repair, and reproduction. • Cell division produces new cells to increase the size of the organism. • Cell division produces new cells to replace damaged and old cells. • Cell division is the method that some organisms use to reproduce. DNA in the nucleus plays a key role in normal cell functions and in cell division. • The nucleus contains the nucleolus and the chromosomes. • DNA is contained in the chromosomes in the nucleus of each cell and carries the genetic information to direct all the activities in the organism. • Genes are segments of DNA on a chromosome. They carry the instructions to make proteins. This information results in individual characteristics. • RNA is a copy of a gene segment of DNA. RNA carries the instructions from genes in the nucleus to the ribosomes, where proteins are made. • Once a cell is large enough to divide, DNA replicates before cell division begins. The cell cycle includes the normal cell functions and cell division. • Cells spend most of their time in interphase, growing and performing their specific functions. • Cell division includes mitosis and cytokinesis. • The stages of mitosis are prophase, metaphase, anaphase, and telophase. • Cytokinesis divides the cytoplasm in two and is different in animal and plant cells. • The products of cell division are two genetically identical daughter cells. Vocabulary nuclear membrane, p. 39 DNA, p. 39 nucleolus, p. 40 centrioles, p. 40 nucleotide, p. 42 nitrogenous bases, p. 42 amino acids, p. 43 gene, p. 44 genome, p. 44 traits, p. 45 cell cycle, p. 49 interphase, p. 49 sister chromatids, p. 49 parent cell, p. 49 daughter cells, p. 49 mitosis, p. 49 cytokinesis, p. 49 prophase, p. 50 68 Unit A Reproduction NEL
Page 1 and 2: 32 NEL
Page 3 and 4: CHAPTER 2 Cell Growth and Reproduct
Page 5 and 6: 2.1 The Importance of Cell Division
Page 7 and 8: 2.1 CHECK YOUR Understanding 1. Giv
Page 9 and 10: Figure 2 Plant cell structures cyto
Page 11 and 12: 2.3 From DNA to Proteins You have l
Page 13 and 14: Did You KNOW? The Human Genome The
Page 15 and 16: LEARNING TIP Think about the sectio
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Page 19 and 20: centrioles nucleus chromosome spind
Page 21 and 22: 2.4 CHECK YOUR Understanding 1. Wha
Page 23 and 24: LEARNING TIP Make connections to yo
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Page 39 and 40: Review Key Ideas and Vocabulary 1.
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Page 43 and 44: 3.1 Meiosis LEARNING TIP Scan the t
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amniotic fluid placenta umbilical c
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Figure 7 The zygote has divided sev
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CORD BLOOD: BIOLOGICAL INSURANCE Sc
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Figure 2 The X chromosome (a) is fa
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4.4 CHECK YOUR Understanding 1. Wha
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Figure 2 The karyotype of Down synd
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4.6 Prenatal Procedures (a) (b) Fig
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4.6 CHECK YOUR Understanding 1. Nam
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4.7 Reproductive Technologies LEARN
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4.7 CHECK YOUR Understanding 1. At
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Sample Stakeholder Perspectives •
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CHAPTER 4 Review Human Reproduction
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Review Key Ideas and Vocabulary 1.
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UNIT A Review Reproduction Unit Sum
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15. Complete the following table to
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