4. Genetic Mapping and Linkage

Genetic linkage mapping for a large number of families identifies 4% recombination between the genes for Rh blood type and elliptocytosis (see Problem 18). At the Rh locus, alleles R and r control Rh+ and Rh- blood types. Allele E producing elliptocytosis is dominant to the wild-type recessive allele e. Tom and Terri each have elliptocytosis, and each is . Tom's mother has elliptocytosis and is Rh- while his father is healthy and has Rh+. Terri's father is Rh+ and has elliptocytosis; Terri's mother is Rh- and is healthy.

What is the probability that the first child of Tom and Terri will be Rh− and have elliptocytosis?

A group of families in which an autosomal dominant condition is present are studied to determine lod scores for possible genetic linkage between three RFLP markers (R1, R2, and R3) and the disease gene. The chart shows lod scores at each of the recombination distances (θ values) tested. Provide an interpretation of the lod score results for each RFLP. Be specific about any significant evidence of genetic linkage.

RFLP                                     θ values
              0.05   0.10   0.15   0.20   0.25   0.30   0.35   0.40
R1           0.5     0.8     1.8     2.2     1.9     0.7     0.2     0.1
R2           1.1     3.1     3.8     3.0     2.1     1.0     0.8     0.1
R3           0.2     0.3     0.1     0.3     0.4     0.6     0.8     0.7

Gene R and gene T are genetically linked. Answer the following questions concerning a dihybrid organism with the genotype Rt/rT:

If r = 0.20, give the expected frequencies of gametes produced by the dihybrid.

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder inherited on human chromosome 17. Part of the analysis mapping the NF1 gene to chromosome 17 came from genetic linkage studies testing segregation of NF1 and DNA genetic markers on various chromosomes. A DNA marker with two alleles, designated 1 and 2, is linked to NF1. The pedigree below shows segregation of NF1 (darkened symbols) and gives genotypes for the DNA marker for each family member. What is the estimated recombination frequency between the NF1 gene and the DNA marker? <

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder inherited on human chromosome 17. Part of the analysis mapping the NF1 gene to chromosome 17 came from genetic linkage studies testing segregation of NF1 and DNA genetic markers on various chromosomes. A DNA marker with two alleles, designated 1 and 2, is linked to NF1. The pedigree below shows segregation of NF1 (darkened symbols) and gives genotypes for the DNA marker for each family member.

Based on the phase of alleles on chromosomes in generation II, is there any evidence of recombination among the eight offspring in generation III? Explain. <>

Neurofibromatosis 1 (NF1) is an autosomal dominant disorder inherited on human chromosome 17. Part of the analysis mapping the NF1 gene to chromosome 17 came from genetic linkage studies testing segregation of NF1 and DNA genetic markers on various chromosomes. A DNA marker with two alleles, designated 1 and 2, is linked to NF1. The pedigree below shows segregation of NF1 (darkened symbols) and gives genotypes for the DNA marker for each family member.

Determine the alleles for the NF1 gene and the DNA marker gene on each chromosome carried by the four family members in generation I and generation II. Use N for the dominant NF1 allele and n for the recessive allele and assume I-1 is heterozygous for the disease allele (Nn). <>

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:                                     Theta (θ) Value               0.01    0.05     0.10     0.20     0.30     0.40SCA5    11.02   12.26   11.94   10.04    7.26     3.77 and DNA marker A SCA5    0.35.    0.94.     1.07     0.99     0.75    0.43 and DNA marker B Based on the available information, is DNA marker A linked to the gene producing SCA5? Explain your answer.

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:                                     Theta (θ) Value               0.01    0.05     0.10     0.20     0.30     0.40SCA5    11.02   12.26   11.94   10.04    7.26     3.77 and DNA marker A SCA5    0.35.    0.94.     1.07     0.99     0.75    0.43 and DNA marker B What is the maximum value for each set of lod scores?

A 2006 genetic study of a large American family (Ikeda et al., 2006) identified genetic linkage between DNA markers on chromosome 11 and the gene producing the autosomal dominant neuromuscular disorder spinocerebellar ataxia type 5 (SCA5). The following lod score data are taken from the 2006 study:                                     Theta (θ) Value               0.01    0.05     0.10     0.20     0.30     0.40SCA5    11.02   12.26   11.94   10.04    7.26     3.77 and DNA marker A SCA5    0.35.    0.94.     1.07     0.99     0.75    0.43 and DNA marker B Does either group of lod scores indicate statistically significant odds in favor of genetic linkage? Explain your answer.