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a specific base sequence called its recognition site. A normal p53 gene is removed intact from its chromosome because there are recognition sites on either side of the gene as indicated by the little pairs of scissors in Figure 1 below. Figure 1. Normal p53 gene. recognition site recognition site DNA p53 gene action of restriction endonuclease p53 gene One of the mutations that destroys the function of p53 substitutes an incorrect base for the correct one. This may result in the introduction of a new restriction site as shown by the arrow below. In the space provided in Figure 2. draw what will result when this piece of DNA is cut by the restriction endonuclease Figure 2. Mutated p53 gene. new site DNA p53 gene action of restriction endonuclease How many pieces would result from cutting the mutated p53 DNA? Are the lengths of the resulting fragments of the mutated p53 DNA the same or different? The difference you just noted between a normal p53 gene and the mutated gene is detectable by gel electrophoresis. Gel electrophoresis is a technique which separates DNA fragments by length. DNA fragments are placed into a well of an agarose gel. Because DNA is negatively charged, the DNA fragments move through the gel toward the positive pole of the chamber when current is applied. The fragments snake their way through microscopic openings in the agarose gel. The smaller the DNA fragment, the more easily it moves through the gel and the further it travels. Larger fragments will move slower and therefore end up closer to the well end of the gel The gel contains ethidium bromide which binds to the DNA fragments. When the gel is placed on an ultraviolet light box, the DNA bands will fluoresce orange. Refer back to Figures 1 and 2 to answer the following two questions. How many bands would be present when a normal p53 gene is cut out of the chromosome? How many bands would be present when a mutated p53 gene is cut out? Because a somatic cell has pairs of chromosomes, each cell has two copies of chromosome 17. So, every time p53 analysis is performed on a tissue sample, there will be two copies of the p53 gene. Realize that the two copies may be the same or they may be different. What are the three different combinations of normal and mutated p53 genes that a person can inherit? (1) (2) (3) Examine the three lanes on the gel located on the next page. (1) Which one (A. B. or C) is from a person with 2 normal copies of p53? (2) Which is from a person with 2 mutated copies of p53? (3) Which is from a person with 1 normal and 1 mutated copy of p53? Lab 12: p53 and the Cell Cycle

          a specific base sequence called its recognition site. A normal p53 gene is removed intact from its chromosome because there are recognition sites on either side of the gene as indicated by the little pairs of scissors in Figure 1 below. Figure 1. Normal p53 gene. recognition site recognition site DNA p53 gene action of restriction endonuclease p53 gene One of the mutations that destroys the function of p53 substitutes an incorrect base for the correct one. This may result in the introduction of a new restriction site as shown by the arrow below. In the space provided in Figure 2. draw what will result when this piece of DNA is cut by the restriction endonuclease Figure 2. Mutated p53 gene. new site DNA p53 gene action of restriction endonuclease How many pieces would result from cutting the mutated p53 DNA? Are the lengths of the resulting fragments of the mutated p53 DNA the same or different? The difference you just noted between a normal p53 gene and the mutated gene is detectable by gel electrophoresis. Gel electrophoresis is a technique which separates DNA fragments by length. DNA fragments are placed into a well of an agarose gel. Because DNA is negatively charged, the DNA fragments move through the gel toward the positive pole of the chamber when current is applied. The fragments snake their way through microscopic openings in the agarose gel. The smaller the DNA fragment, the more easily it moves through the gel and the further it travels. Larger fragments will move slower and therefore end up closer to the well end of the gel The gel contains ethidium bromide which binds to the DNA fragments. When the gel is placed on an ultraviolet light box, the DNA bands will fluoresce orange. Refer back to Figures 1 and 2 to answer the following two questions. How many bands would be present when a normal p53 gene is cut out of the chromosome? How many bands would be present when a mutated p53 gene is cut out? Because a somatic cell has pairs of chromosomes, each cell has two copies of chromosome 17. So, every time p53 analysis is performed on a tissue sample, there will be two copies of the p53 gene. Realize that the two copies may be the same or they may be different. What are the three different combinations of normal and mutated p53 genes that a person can inherit? (1) (2) (3) Examine the three lanes on the gel located on the next page. (1) Which one (A. B. or C) is from a person with 2 normal copies of p53? (2) Which is from a person with 2 mutated copies of p53? (3) Which is from a person with 1 normal and 1 mutated copy of p53? Lab 12: p53 and the Cell Cycle

a specific base sequence called its recognition site. A normal p53 gene is removed intact from its chromosome because there are recognition sites on either side of the gene as indicated by the little pairs of scissors in Figure 1 below. Figure 1. Normal p53 gene. recognition site recognition site DNA p53 gene action of restriction endonuclease p53 gene One of the mutations that destroys the function of p53 substitutes an incorrect base for the correct one. This may result in the introduction of a new restriction site as shown by the arrow below. In the space provided in Figure 2. draw what will result when this piece of DNA is cut by the restriction endonuclease Figure 2. Mutated p53 gene. new site DNA p53 gene action of restriction endonuclease How many pieces would result from cutting the mutated p53 DNA? Are the lengths of the resulting fragments of the mutated p53 DNA the same or different? The difference you just noted between a normal p53 gene and the mutated gene is detectable by gel electrophoresis. Gel electrophoresis is a technique which separates DNA fragments by length. DNA fragments are placed into a well of an agarose gel. Because DNA is negatively charged, the DNA fragments move through the gel toward the positive pole of the chamber when current is applied. The fragments snake their way through microscopic openings in the agarose gel. The smaller the DNA fragment, the more easily it moves through the gel and the further it travels. Larger fragments will move slower and therefore end up closer to the well end of the gel The gel contains ethidium bromide which binds to the DNA fragments. When the gel is placed on an ultraviolet light box, the DNA bands will fluoresce orange. Refer back to Figures 1 and 2 to answer the following two questions. How many bands would be present when a normal p53 gene is cut out of the chromosome? How many bands would be present when a mutated p53 gene is cut out? Because a somatic cell has pairs of chromosomes, each cell has two copies of chromosome 17. So, every time p53 analysis is performed on a tissue sample, there will be two copies of the p53 gene. Realize that the two copies may be the same or they may be different. What are the three different combinations of normal and mutated p53 genes that a person can inherit? (1) (2) (3) Examine the three lanes on the gel located on the next page. (1) Which one (A. B. or C) is from a person with 2 normal copies of p53? (2) Which is from a person with 2 mutated copies of p53? (3) Which is from a person with 1 normal and 1 mutated copy of p53? Lab 12: p53 and the Cell Cycle

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