4. Genetic Mapping and Linkage

Mapping Genes

Open Question
DNA sequences for 10 individuals are

Nucleotide Position
1 5 10
Person 1 ...GACCTATTGC...
Person 2 ...GAACTATTGC...
Person 3 ...GACCTTTTGC...
Person 4 ...GACCTATTGC...
Person 5 ...CAACTATTGC...
Person 6 ...GACCTTTTGC...
Person 7 ...CAACTATTGC...
Person 8 ...GACCTATTGC...
Person 9 ...CAACTATTGC...
Person 10 ...GAACTATTGC...

Identify the haplotype carried by each person.
Open Question
DNA sequences for 10 individuals are

Nucleotide Position
1 5 10
Person 1 ...GACCTATTGC...
Person 2 ...GAACTATTGC...
Person 3 ...GACCTTTTGC...
Person 4 ...GACCTATTGC...
Person 5 ...CAACTATTGC...
Person 6 ...GACCTTTTGC...
Person 7 ...CAACTATTGC...
Person 8 ...GACCTATTGC...
Person 9 ...CAACTATTGC...
Person 10 ...GAACTATTGC...

What is the sequence of each haplotype?
Open Question
DNA sequences for 10 individuals are

Nucleotide Position
1 5 10
Person 1 ...GACCTATTGC...
Person 2 ...GAACTATTGC...
Person 3 ...GACCTTTTGC...
Person 4 ...GACCTATTGC...
Person 5 ...CAACTATTGC...
Person 6 ...GACCTTTTGC...
Person 7 ...CAACTATTGC...
Person 8 ...GACCTATTGC...
Person 9 ...CAACTATTGC...
Person 10 ...GAACTATTGC...

How many different SNP haplotypes are represented in the data?
Open Question
DNA sequences for 10 individuals are

Nucleotide Position
1 5 10
Person 1 ...GACCTATTGC...
Person 2 ...GAACTATTGC...
Person 3 ...GACCTTTTGC...
Person 4 ...GACCTATTGC...
Person 5 ...CAACTATTGC...
Person 6 ...GACCTTTTGC...
Person 7 ...CAACTATTGC...
Person 8 ...GACCTATTGC...
Person 9 ...CAACTATTGC...
Person 10 ...GAACTATTGC...

Identify the nucleotide positions of all SNPs (single nucleotide polymorphisms).
Open Question
How would the results vary in cross (a) of Problem 32 if genes A and B were linked with no crossing over between them? How would the results of cross (a) vary if genes A and B were linked and 20 map units (mu) apart?
Open Question
Because of the relatively high frequency of meiotic errors that lead to developmental abnormalities in humans, many research efforts have focused on identifying correlations between error frequency and chromosome morphology and behavior. Tease et al. (2002) studied human fetal oocytes of chromosomes 21, 18, and 13 using an immunocytological approach that allowed a direct estimate of the frequency and position of meiotic recombination. Below is a summary of information [modified from Tease et al. (2002)] that compares recombination frequency with the frequency of trisomy for chromosomes 21, 18, and 13. (Note: You may want to read appropriate portions of Chapter 8 for descriptions of these trisomic conditions.)Trisomic Mean Recombination Live-bornFrequency FrequencyChromosome 21 1.23 1/700Chromosome 18 2.36 1/3000–1/8000Chromosome 13 2.50 1/5000–1/19,000What conclusions can be drawn from these data in terms of recombination and nondisjunction frequencies? How might recombination frequencies influence trisomic frequencies?
Open Question
Based on previous family studies, an autosomal recessive disease with alleles A and a is suspected to be linked to an RFLP marker. The RFLP marker has four alleles, R₁, R₂, R₃, and R₄. The accompanying pedigree shows a three-generation family in which the disease is present. The gel shows the RFLP alleles for each family member directly below the pedigree symbol for that person. After determining the genotypes for the RFLP and disease gene for each family member, answer the following questions.Based on your analysis, what is the recombination frequency in this family? Explain how you obtained your answer.
Open Question
Based on previous family studies, an autosomal recessive disease with alleles A and a is suspected to be linked to an RFLP marker. The RFLP marker has four alleles, R₁, R₂, R₃, and R₄. The accompanying pedigree shows a three-generation family in which the disease is present. The gel shows the RFLP alleles for each family member directly below the pedigree symbol for that person. After determining the genotypes for the RFLP and disease gene for each family member, answer the following questions.Is there any evidence of recombination in this pedigree? If so, identify the recombinant individuals and illustrate the recombination that has occurred.
Open Question
Based on previous family studies, an autosomal recessive disease with alleles A and a is suspected to be linked to an RFLP marker. The RFLP marker has four alleles, R₁, R₂, R₃, and R₄. The accompanying pedigree shows a three-generation family in which the disease is present. The gel shows the RFLP alleles for each family member directly below the pedigree symbol for that person. After determining the genotypes for the RFLP and disease gene for each family member, answer the following questions.What is the most likely arrangement of syntenic alleles for the RFLP and the disease gene in I-1 and I-2?
Open Question
For six genes known to be linked on chromosome 10 of corn (Zea mays), the recombination frequencies between various pairs have been determined in a series of genetic crosses. Use the recombination frequency data in the table below to determine the order of and distance between the genes on a genetic map. The gene lc1 is known to be closest to the telomere of the chromosome.