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Ch. 15 - Recombinant DNA Technology and Its Applications
Sanders - Genetic Analysis: An Integrated Approach 3rd Edition
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
All textbooksSanders 3rd EditionCh. 15 - Recombinant DNA Technology and Its ApplicationsProblem E.10a
Chapter 15, Problem E.10a

The frequencies of the four alleles contributed to the child by possible father F1 in Problem 7 are 0.18, 0.23, 0.13, and 0.14. Calculate the Combined Paternity Index (CPI) for the four genes in this analysis.

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Understand that the Combined Paternity Index (CPI) is the product of the Paternity Indices (PIs) for each gene or allele tested. The PI for each gene is calculated based on the allele frequency contributed by the alleged father.
Recall that the Paternity Index (PI) for a single allele is calculated as the reciprocal of the allele frequency if the alleged father is homozygous for that allele, or as 1 divided by twice the allele frequency if the alleged father is heterozygous. Since the problem only provides allele frequencies, assume the simplest case where PI = 1 / allele frequency for each allele.
Write down the allele frequencies given: f_1=0.18, f_2=0.23, f_3=0.13, f_4=0.14.
Calculate the PI for each allele using the formula PI_i = 1 / f_i. This means you will compute PI_1 = 1/0.18, PI_2 = 1/0.23, PI_3 = 1/0.13, and PI_4 = 1/0.14.
Multiply all the individual PIs together to get the Combined Paternity Index: CPI = PI_1 \times PI_2 \times PI_3 \times PI_4. This product gives the overall likelihood ratio supporting paternity based on the four alleles.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Allele Frequency

Allele frequency refers to how common a specific allele is within a population. It is expressed as a proportion or percentage and is crucial in genetic analyses to estimate the likelihood of an individual carrying a particular allele. In paternity testing, allele frequencies help calculate the probability that a random individual from the population could contribute the observed alleles.
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Paternity Index (PI)

The Paternity Index is a likelihood ratio that compares the probability of the alleged father transmitting a specific allele to the child versus a random man from the population. It is calculated for each genetic marker and reflects how strongly the genetic evidence supports paternity. A higher PI indicates stronger evidence that the tested man is the biological father.
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Combined Paternity Index (CPI)

The Combined Paternity Index is the product of individual Paternity Indices across multiple genetic loci. It aggregates the evidence from all tested markers to provide an overall likelihood ratio supporting paternity. The CPI is used to calculate the probability of paternity, with higher values indicating stronger genetic evidence that the tested man is the biological father.
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Related Practice
Textbook Question

In an inheritance case, a man has died leaving his estate to be divided equally between 'his wife and his offspring.' His wife (M) has an adult daughter (D), and they argue that they should split the estate equally. As a young couple, however, the man and his wife had a son that they gave up for adoption. Two men have appeared, each claiming to be the son of the couple and therefore entitled to a one-third share of the estate. The accompanying illustration shows the results of DNA analysis for five genes for the mother (M), her daughter (D), and the two claimants (S1 and S2). Do the DNA results suggest that either man is likely to be the son of the man and his wife? Explain.

Textbook Question

Additional STR allele frequency information can be added to improve the analysis in Problem 8. The frequency of D8S1179₁₂ = 0.12. The frequency of D16S539₁₈ = 0.08 and of D16S539₂₀ = 0.21. Lastly, D18S51₁₉ = 0.13 and D18S51₂₀ = 0.10. Combine the allele frequency information for these three STR genes with the information used in Problem 8 to calculate the frequency of the genotype for six of the STR genes.

Textbook Question
Why are diseases of the blood simpler targets for treatment by gene therapy than are many other genetic diseases?
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Textbook Question

The frequencies of the four alleles contributed to the child by possible father F1 in Problem 7 are 0.18, 0.23, 0.13, and 0.14. Make a statement about the possible paternity of F1 based on this analysis.

Textbook Question

Injection of double-stranded RNA can lead to gene silencing by degradation of RNA molecules complementary to either strand of the dsRNA. Could RNAi be used in gene therapy for a defect caused by a recessive allele? A dominant allele? If so, what might be the major obstacle to using RNAi as a therapeutic agent?

Textbook Question

In an inheritance case, a man has died leaving his estate to be divided equally between 'his wife and his offspring.' His wife (M) has an adult daughter (D), and they argue that they should split the estate equally. As a young couple, however, the man and his wife had a son that they gave up for adoption. Two men have appeared, each claiming to be the son of the couple and therefore entitled to a one-third share of the estate. The accompanying illustration shows the results of DNA analysis for five genes for the mother (M), her daughter (D), and the two claimants (S1 and S2). How many nonmaternal DNA bands are shared by D and S1? By D and S2?