Download Sickle Cell Mutation WS - Lincoln Park High School

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Sickle Cell Allele Mutation WS
Sickle cell disease is a disorder that gets its name from the sickle shape of red blood cells (RBCs) which normally have a
round, disk-like shape. The sickle-shaped RBCs are caused by a faulty hemoglobin resulting from a point mutation in
which just one nucleotide base is changed in the gene that codes for the alpha subunit polypeptide of hemoglobin. When
oxygen levels in the red blood cells are low, the hemoglobin molecules clump together within red blood cells, causing
them to acquire a sickle shape. This is dangerous because these cells can block blood flow in narrow capillaries that lead to
vital organs, cutting off the oxygen supply and leading to cell death. Use your knowledge of base-pairing and the mRNA
genetic code chart at the bottom of the page to complete the table below.
Segment of normal hemoglobin allele
DNA
template
(gene)
mRNA
codons
tRNA
anticodons
Amino
acids
ATGCTCGCA
Same segment of sickle cell hemoglobin
allele
ATGCACGCA
1. How many CODONS are there in this portion of the gene? _____
2. How many NUCLEOTIDES code for one amino acid? _____
3. Is the point mutation in the sickle cell allele a substitution, insertion, or
deletion of a nucleotide? _________________
4. The gene coding for the alpha-subunit polypeptide of hemoglobin is
actually 423 nucleotides long. How many amino acids long is the
alpha-subunit? _______
5. A silent mutation is one that does not affect the amino acid sequence of the gene’s protein product. Create a
substitution mutation in the normal hemoglobin DNA sequence provided in the chart so that the final protein is
unaffected (i.e., the amino acid sequence does not change). Point out the altered mRNA codon that codes for the
same amino acid as the original codon.