Although the capture and trading of great apes has been banned in 112 countries since 1973, it is estimated that about 1000 chimpanzees are removed annually from Africa and smuggled into Europe, the United States, and Japan. This illegal trade is often disguised by simulating births in captivity. Until recently, genetic identity tests to uncover these illegal activities were not used because of the lack of highly polymorphic markers (markers that vary from one individual to the next) and the difficulties of obtaining chimpanzee blood samples. A study was reported in which DNA samples were extracted from freshly plucked chimpanzee hair roots and used as templates for PCR. The primers used in these studies flank highly polymorphic sites in human DNA that result from variable numbers of tandem nucleotide repeats. Several offspring and their putative parents were tested to determine whether the offspring were 'legitimate' or the product of illegal trading. The data are shown in the following Southern blot.
Examine the data carefully and choose the best conclusion.
a. None of the offspring are legitimate.
b. Offspring B and C are not the products of these parents and were probably purchased on the illegal market. The data are consistent with offspring A being legitimate.
c. Offspring A and B are products of the parents shown, but C is not and was therefore probably purchased on the illegal market.
d. There are not enough data to draw any conclusions. Additional polymorphic sites should be examined.
e. No conclusion can be drawn because 'human' primers were used. <>
Ch. 20 - Recombinant DNA Technology
Chapter 19, Problem 18
To estimate the number of cleavage sites in a particular piece of DNA with a known size, you can apply the formula N/4ⁿ where N is the number of base pairs in the target DNA and n is the number of bases in the recognition sequence of the restriction enzyme. If the recognition sequence for BamHI is GGATCC and the phage DNA contains approximately 48,500 bp, how many cleavage sites would you expect?
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Identify the variables in the problem: N is the number of base pairs in the DNA, which is 48,500 bp, and n is the number of bases in the recognition sequence for BamHI, which is GGATCC.
Determine the length of the recognition sequence: Count the number of bases in GGATCC, which is 6.
Apply the formula for estimating the number of cleavage sites: Use the formula \( \frac{N}{4^n} \) where N is 48,500 and n is 6.
Calculate the denominator: Compute \( 4^6 \) to find the total number of possible sequences of length 6.
Divide the total number of base pairs by the number of possible sequences: Use \( \frac{48,500}{4^6} \) to estimate the number of cleavage sites for BamHI in the DNA.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Restriction Enzymes
Restriction enzymes are proteins that cut DNA at specific sequences, known as recognition sites. Each enzyme recognizes a particular sequence of nucleotides, allowing for targeted DNA manipulation. For example, BamHI recognizes the sequence GGATCC and cleaves the DNA at this site, which is crucial for cloning and genetic engineering.
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Mapping with Markers
Base Pairs and DNA Size
DNA is composed of nucleotides, which pair up to form base pairs (A-T and C-G). The size of DNA is often measured in base pairs (bp), indicating the total number of nucleotide pairs in a DNA molecule. Understanding the size of the DNA in base pairs is essential for calculating the potential number of cleavage sites using restriction enzymes.
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Probability of Cleavage Sites
The formula N/4ⁿ estimates the expected number of cleavage sites in a DNA sequence, where N is the total number of base pairs and n is the length of the recognition sequence. This formula is based on the assumption that each base in the recognition sequence can be any of the four nucleotides (A, T, C, G), allowing for a probabilistic approach to predict how many times the enzyme will cut the DNA.
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Related Practice
Textbook Question
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Textbook Question
The Age of Genetics was created by remarkable advances in the use of biotechnology to manipulate plant and animal genomes. Given that the world population reached 7.5 billion people in 2017 and is expected to reach 9.7 billion in 2050, some scientists have proposed that only the worldwide introduction of genetically modified (GM) foods will increase crop yields enough to meet future nutritional demands. Pest resistance, herbicide, cold, drought, and salinity tolerance, along with increased nutrition, are seen as positive attributes of GM foods. However, others caution that unintended harm to other organisms, reduced effectiveness to pesticides, gene transfer to nontarget species, allergenicity, and as yet unknown effects on human health are potential concerns regarding GM foods. If you were in a position to control the introduction of a GM primary food product (rice, for example), what criteria would you establish before allowing such introduction?
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Textbook Question
Variable number tandem repeats (VNTRs) are repeating DNA sequences of about 15–100 bp in length, found both within and between genes. Why are they commonly used in forensics?
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Textbook Question
The National Institutes of Health created the Genetic Testing Registry (GTR) to increase transparency by publicly sharing information about the utility of their tests, research for the general public, patients, health-care workers, genetic counselors, insurance companies, and others. The Registry is intended to provide better information to patients, but companies involved in genetic testing are not required to participate. Should company participation be mandatory? Why or why not? Explain your answers.
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Textbook Question
In a typical PCR reaction, describe what is happening in stages occurring at temperature ranges (a) 92-26 °C, (b) 45-65 °C, and (c) 65-75 °C.
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Textbook Question
Should the FDA regulate direct-to-consumer genetic tests, or should these tests be available as a 'buyer beware' product?
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