Cystic fibrosis (CF) is an autosomal recessive disorder. Several different individual point mutations in the CFTR gene cause cystic fibrosis. Two of the most common mutations (A and B) are shown on the diagram below. The lines below the gene represent ASO (allele-specific oligonucleotide) probes and the regions of the gene to which they hybridize. The "wild type" probe hybridizes to the wild type allele and the "mutant" probe hybridizes to the mutant allele of this gene. A B CFTR gene Probe 1 wild type Probe 3 wild type Probe 2 mutant Probe 4 mutant Five people underwent ASO testing for cystic fibrosis using all four of the probes shown below. The results of this test are shown in the diagram. #1 #2 #3 #4 #5 Probe 1 Probe 2 Probe 3 Probe 4

A RFLP is discovered that is linked to the gene for Duchenne’s muscular dystrophy (DMD). DMD is an X-linked, recessive trait. The RFLP is 2 map units from the gene for DMD. Consider the following pedigree and Southern blot using a probe that hybridizes to the RFLP.     Which band/s is/are associated with DMD? What is the genotype for individuals 3 and 4? (Remember, this is an X linked disease, so use X’s and Y’s to denote). Individual 9 married a man who does NOT have muscular dystrophy, and she is pregnant. DMD is an X-linked trait. What is the probability for their child to have DMD?  An amniocentesis is performed and it is determined that 9’s child in utero has only a 10 kb band that hybridizes to the same probe used above. What can you say about the child now?

Leber Congenital Amaurosis (LCA) causes progressive vision loss due to defects in the gene that encodes RPE65 isomerase.  Affected individuals are homozygous recessive for mutant alleles of the RPE65 gene.  You are trying to determine the molecular nature of the mutations in three individuals with LCA.  For ease of analysis, you may assume that each individual is homozygous for the same mutant allele (though the three individuals have different mutations than each other).   You use the polymerase chain reaction to amplify DNA from each patient and you determine the sequence of the DNA and compare it to unaffected individuals.  You identify the following differences.  Note that the non-template strand of DNA is given and the changes are highlighted using red boldface.  You can assume that the sequences are in the first reading frame (eg. the first three nucleotides of each sequence is a codon).   The coding region of the gene is 1602 bp and the position of the sequences shown below is…

You have a patient in your clinic presenting symptoms of cystic fibrosis. You screen their CFTR gene for mutations, and find the following list: CFTR 320 L V CFTR 341 S W CFTR 528 E D CFTR 976 F Q CFTR 1235 S R Which mutation(s) are likely causing cystic fibrosis in this patient? You also sequence a newborn family member of this patient. They have all of these same mutations, other than the one at position 976, and no other mutations in CFTR. Do you predict this person will develop cystic fibrosis? Explain why.