1. Treacher Collins syndrome is a condition that affects the development of bone
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Question
1. Treacher Collins syndrome is a condition that affects the development of bones and other tissues of the face. It is an autosomal dominant condition and results from mutations in the TCOF1 gene. There is a SNP that is linked to the mutant (Treacher Collin's) allele. The normal allele has two BamHI sites and the SNP creates a new BamHl site, that is not present in the normal allele. A map shows the location of the BamHI sites on the two alleles of the TCOF1 region of the genome and the sizes of the fragments after digestion. DNA was isolated from nine individuals and the TCOF1 region of the genome was amplified by PCR. The arrows on each map mark the positions of the primers used for the PCR experiment. The PCR product was then cut with the restriction enzyme BamHI and run on an agarose gel (Lanes 1-9 are marked below the gel and represent Individuals 1 -9). Maps of the Two Alleles of the TCOF1 Gene Region amHI BamHI BamHI BamHI BamHI 1.5 kb 1.7 klb kb Size (in kb a. On each line to the right of the gel write the size (in kb) for each fragment. What is the size(s) of the fragment(s) that correspond to the allele associated with Treacher Collin's? b. Use T and t to define your alleles and write the genotypes of the following individuals: c. i. Individual 2: ii. Individual 3: ii Individual 4: For ALL 9 individuals with DNA analysis performed, which ones will have Treacher Collin's disorder (assuming 100% penetrance and expressivity)? d. The primers were used in the PCR analysis above to specifically identify the TCOF1 gene. If a Southern blot was performed (instead of PCR analysis), what would be needed for identification of the RFLP in the TCOF1 gene? e.Explanation / Answer
WT allele = 1.7 kb fragment
Mutant allele = 1.5 + 1.2 kb fragments
Gel bands:
Lowest band = 0.2 kb
Intermediate band = 1.5 kb
Top band = 1.7 kb
The band associated with the WT allele = Top band = 1.7 kb
Bands associated with the mutant allele = Lowest band (0.2 kb) and intermediate band (1.5 kb).
Individual 2 = TdTd
Individual 3 = TTd
Individual 2 = TT
Individuals which have at least one allele would should mutant phenotype = 1, 2, 3, 6 and 9.
We need a complementary probe to detect bands in the Southern blotting.
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