GeneGateway Workbook Answers
http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/ggworkbook1.pdf
Hereditary Hemochromatosis Worksheet
Questions for Activity #1
1) Hemochromatosis is an iron load disorder with characteristics: cirrhosis of the liver, diabetes,
hypermelanotic pigmentation of skin, heart failure. A type of cancer, primary hepatocellular
carcinoma sometimes occurs and is found in one third of the deaths by this condition.
Treatment = bleeding or therapeutic phlebotomy in precirrhotic stages to remove a volume of
blood to help lower the amount of iron.
2) gene symbol HLA
gene locus 6p21.3
3) Description: A missense mutation in a highly conserved section in the HFE gene causes a
cys282-to-tyr (C282Y) substitution. This mutation disrupts the structure and function of the
MHC class I protein, which in turn affects its iron absorption from blood.
Questions for Activity #2
1) Top half of chromosome 6 on the short arm
2) 1528 total genes
3) 266 genes in region (may depend on region selected)
4) 26 phenotypes in region (may depend on region selected)
Questions for Activity #3
1) Function of the gene’s membrane protein product is to regulate proper iron absorption in the
body by regulating interaction of the transferrin receptor with transferrin.
2) 9,610 base pairs
3) 7 exons
4) 297 bp of exon 1
5) CDS 1047bp
6) exon 1: 297-221 no codant = 76
7) 2727bp mRNA
8) 2727 mRNA polyA – 1047 CDS = 1680bp
Questions for Activity #4 and #5
1) Underline amino acids 23 through 348 or the end of the sequence
2) The two small purple chains are the beta-2-microglobulin, the green and blue chains are HFE
3) The disulfide bond between cysteines 225 and 282 of chain A is lost when the mutation
C282Y occurs.