Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

18. Molecular Genetic Tools

Methods for Analyzing DNA

Genetics

18. Molecular Genetic Tools

Methods for Analyzing DNA

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2:54 minutes

Problem E.8

Textbook Question

Figure E.1 illustrates the results of an electrophoretic analysis of 13 CODIS STR markers on a DNA sample and identifies the alleles for each gene. Table E.2 lists the frequencies for alleles of three of the STRs shown in the figure. Use this information to calculate the frequency of the genotype for STR genes FGA, vWA, and D3S1358 given in Figure E.1.

Verified step by step guidance

Identify the alleles for each STR gene (FGA, vWA, and D3S1358) from the electrophoretic analysis results shown in Figure E.1. Note whether the genotype is homozygous (same alleles) or heterozygous (different alleles) for each STR.

Locate the allele frequencies for each identified allele of the three STR genes in Table E.2. These frequencies represent the proportion of each allele in the population.

For each STR gene, calculate the genotype frequency using the Hardy-Weinberg principle: if the genotype is homozygous (allele A and allele A), use the formula

p^2

, where

p

is the frequency of allele A; if heterozygous (allele A and allele B), use the formula

2 q

, where

p

and

q

are the frequencies of alleles A and B respectively.

Calculate the genotype frequency for each of the three STR genes separately by substituting the allele frequencies into the appropriate formula from step 3.

Multiply the genotype frequencies of the three STR genes together to find the combined genotype frequency for the individual, assuming the loci are independent and in Hardy-Weinberg equilibrium.

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Key Concepts

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

Short Tandem Repeats (STRs)

STRs are short sequences of DNA, typically 2-6 base pairs long, repeated multiple times in a row at specific loci. They are highly polymorphic, making them useful for genetic identification and forensic analysis. Each individual has two alleles per STR locus, inherited from each parent.

Allele Frequency and Genotype Frequency

Allele frequency is the proportion of a specific allele variant in a population. Genotype frequency refers to how often a particular combination of alleles (genotype) occurs. For STRs, genotype frequency can be calculated using allele frequencies, assuming Hardy-Weinberg equilibrium.

Hardy-Weinberg Equilibrium

This principle states that allele and genotype frequencies in a large, randomly mating population remain constant across generations if no evolutionary forces act. It allows calculation of genotype frequencies from allele frequencies using the formula p² + 2pq + q² = 1, where p and q are allele frequencies.

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Textbook Question

The results shown are from a DNA test for four genes used in a paternity identification case. DNA for the mother (M) and her child (C) are shown along with DNA from two possible fathers, F1 and F2. What can you conclude based on the DNA results available?

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Textbook Question

The results shown are from a DNA test for four genes used in a paternity identification case. DNA for the mother (M) and her child (C) are shown along with DNA from two possible fathers, F1 and F2. Based on the exclusion principle, is either man excluded as the possible father? Explain.

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Textbook Question

The results shown are from a DNA test for four genes used in a paternity identification case. DNA for the mother (M) and her child (C) are shown along with DNA from two possible fathers, F1 and F2. In the 'C' column, label the DNA bands contributed by the mother with 'M' and the DNA bands contributed by the father with 'F.'

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Textbook Question

As genetic testing becomes widespread, medical records will contain the results of such testing. Who should have access to this information? Should employers, potential employers, or insurance companies be allowed to have this information? Would you favor or oppose having the government establish and maintain a central database containing the results of individuals' genome scans?

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Might it make sense someday to sequence every newborn's genome at the time of birth? What are the potential advantages and concerns of this approach?

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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.

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