Multiple Choice
In eukaryotic cells, the core structural and catalytic components of the ribosome are primarily composed of which type of RNA?
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5. DNA to RNA to Protein
tRNA, rRNA and the Codon Code
Multiple Choice
In the classic sickle-cell mutation affecting the β-globin (HBB) gene, which DNA coding-strand codon is altered (at codon 6) compared with the normal sequence?
A
GTG is changed to GAG
B
GAG is changed to GTG
C
GAC is changed to GTC
D
GAG is changed to GAA
Verified step by step guidance1
Recall that the β-globin gene mutation responsible for sickle-cell disease occurs at codon 6 of the HBB gene, which affects the amino acid sequence of the β-globin protein.
Understand that the mutation involves a single nucleotide substitution in the DNA coding strand, which changes the codon from one sequence to another, altering the encoded amino acid.
Identify the normal codon at position 6 in the DNA coding strand, which codes for glutamic acid (Glu). This codon is GAG in the DNA coding strand.
Recognize that the sickle-cell mutation changes this codon from GAG to GTG, which codes for valine (Val), causing the structural change in hemoglobin.
Therefore, the correct description of the mutation is that the DNA coding-strand codon GAG is changed to GTG at codon 6.
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