Question

Gyrate atrophy is a degeneration of the retina that begins in late adolescence as night blindness and progresses to blindness. The cause is mutation in the gene that encodes a mitochondrial enzyme, ornithine aminotransferase (OAT), on chromosome 10. This autosomal recessive inborn error of metabolism causes build up in body fluids of ornithine, which derives from the amino acid arginine, found in dietary protein. Researchers sequenced the OAT gene for five patients with the following results:

Patient A: A change in codon 209 of UAU to UAA

Patient B: A change in codon 299 of UAC to UAG

Patient C: A change in codon 426 of CGA to UGA

Patient D: A 2 base deletion at codons 64 and 65 that results in a UGA codon at position 79

Patient E: Exon 6, including 1,071 bases, is entirely deleted.

1. Another patient, F, has the mutations seen in patients A and B. How is this possible?

Answer 1

It is an autosomal recessive disorder. If the offspring (patient F) produced from patients A and B married.                                                 

                                                            aa Patient A   X bb Patient B

                                                              ab patient F