6 20 pts Hemophilia is an Xlinked recessive disorder charact

6.) (20 pts) Hemophilia is an X-linked recessive disorder characterized by the inability to form blood clots properly. This occurs because a critical blood-clotting gene is carried on the X chromosome. Hemophilia has played an important role in Europe\'s history, for it appeared in the children of Great Britain\'s Queen Victoria. It became known as the \"Royal disease\" because it spread to the royal families of Europe through Victoria\'s descendants. The molecular defect of the Royal disease has been determined. The gene F9 encodes the protein Factor IX, a protein required for blood clotting. Part of the DNA sequence for Factor IX is shown below. The exons are underlined. This is coding DNA sequence. AAG CAG TAT GTT GTAAGCA. GGA GAT CAG TGT exon 4 exon 3 GAG TCC AAT CCA TGT TTA more exon 4 A) Translate the wild type sequence, using the reading frame shown by the spacing. Write the amino acids using the three-letter code above the DNA sequence. B.) In the mutant allele the A under the asterisk is substituted by a G (asterisk below). AAG CAG TAT GTT GGTAAGCA... ...CTATCTCAGAG AT GGA GAT CAG TGT exon 3 (part B continues on the next page) GAG TCC AAT CCA TGT TTA more exon 4

Solution

Answers:

6. A.

Lys Gln Tyr Val Asp Gly Asp Gln Cys Glu Ser Asn Pro Cys Leu

AAG CAG TAT GTT GAT GGA GAT CAG TGT GAG TCC AAT CCA TGT TTA

B. Splicing. The mutation introduces a new splice acceptor, AG.

C. Lys Gln Tyr Val Glu Arg Trp Arg Ser Val Stop

AAG CAG UAU GUU GAG AGA UGG AGA UCA GUG UGA GUC

D. Please refer to answer C above.

E. The mutation caused a frame shift, which introduced six wrong amino acids and then a stop codon. The encoded F9 protein from this sequence is faulty with premature truncation, so it should not be functional.