Question 21.7: Use three-letter and one-letter abbreviations to write the a...
Use three-letter and one-letter abbreviations to write the amino acid sequence for the peptide from the mRNA sequence of 5′ UCA AAA GCC CUU 3′.
Each of the codons specifies a particular amino acid. Using TABLE 21.6, we write a peptide with the following amino acid sequence:
mRNA codons: 5′ \boxed{UCA} \boxed{AAA} \boxed{GCC} \boxed{CUU} 3′
\downarrow \downarrow \downarrow \downarrowAmino acid sequence: \boxed{Ser} \boxed{Lys} \boxed{Ala} \boxed{Leu} . SKAL
| TABLE 21.6 Codons in mRNA: The Genetic Code for Amino Acids | |||||
| First Letter | Second letter | Third Letter | |||
| U | C | A | G | ||
| U | \left. \begin{array}{l}UUU\\UUC\end{array} \right\} Phe(F)
\left. \begin{array}{l}UUA\\UUG\end{array} \right\} Leu(L) |
\left. \begin{array}{l}UCU\\UCC\\UCA\\UCG\end{array} \right\} Ser(S) | \left. \begin{array}{l}UAU\\UAC\end{array} \right\} Tyr(Y)
UAA STOP^{b} UAG STOP^{b} |
\left. \begin{array}{l}UGU\\UGC\end{array} \right\} Cys (C)
UGA STOP^{b} UGG Trp(W) |
U C A G |
| C | \left. \begin{array}{l}CUU\\CUC\\CUA\\CUG\end{array} \right\} Leu (L) | \left. \begin{array}{l}CCU\\CCC\\CCA\\CCG\end{array} \right\} Pro (P) | \left. \begin{array}{l}CAU\\CAC\end{array} \right\} His (H)
\left. \begin{array}{l}CAA\\CAG\end{array} \right\} Gln (Q) |
\left. \begin{array}{l}CGU\\CGC\\CGA\\CGG\end{array} \right\} Arg (R) |
U C A G |
| A | \left. \begin{array}{l}AUU\\AUC\\AUA\end{array} \right\} Ile (I)
AUG START^{a}/Met(M) |
\left. \begin{array}{l}ACU\\ACC\\ACA\\ACG \end{array} \right\} Thr (T) | \left. \begin{array}{l}AAU\\AAC \end{array} \right\} Asn (N)
\left. \begin{array}{l}AAA\\AAG \end{array} \right\} Lys (K) |
\left. \begin{array}{l}AGU\\AGC \end{array} \right\} Ser (S)
\left. \begin{array}{l}AGA\\AGG \end{array} \right\} Arg (R) |
U C A G |
| G | \left. \begin{array}{l}GUU\\GUC\\GUA\\GUG \end{array} \right\} Val (V) | \left. \begin{array}{l}GCU\\GCC\\GCA\\GCG \end{array} \right\} Ala (A) | \left. \begin{array}{l}GAU\\GAC \end{array} \right\} Asp (D)
\left. \begin{array}{l}GAA\\GAG \end{array} \right\} Glu (E) |
\left. \begin{array}{l}GGU\\GGC\\GGA\\GGG \end{array} \right\} Gly (G) |
U C A G |
| START^{a} codon signals the initiation of a peptide chain. STOP^{b} codons signal the end of a peptide chain. |
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