11. Translation

The Genetic Code

Open Question
M. Klemke et al. (2001) discovered an interesting coding phenomenon in which an exon within a neurologic hormone receptor gene in mammals appears to produce two different protein entities ( and ALEX). Following is the DNA sequence of the exon's end derived from a rat.

5'-gtcccaaccatgcccaccgatcttccgcctgcttctgaagATGCGGGCCCAG

The lowercase letters represent the initial coding portion for the protein, and the uppercase letters indicate the portion where the ALEX entity is initiated. (For simplicity, and to correspond with the RNA coding dictionary, it is customary to represent the coding (non-template) strand of the DNA segment.)

Convert the coding DNA sequence to the coding RNA sequence.
Open Question
An experiment by Khorana and his colleagues translated a synthetic mRNA containing repeats of the trinucelotide UUG.

How many reading frames are possible in this mRNA?
Open Question
In an experiment to decipher the genetic code, a poly-AC mRNA (ACACACAC...) is synthesized. What pattern of amino acids would appear if this sequence were to be translated by a mechanism that reads the genetic code as

a quadruplet without overlaps?
Open Question
Figure 9.17 shows three posttranslational steps required to produce the sugar-regulating hormone insulin from the starting polypeptide product preproinsulin.

Explain why it is not feasible to insert the entire human insulin gene into E. coli and anticipate the production of insulin.
Open Question
A short RNA molecule was isolated that demonstrated a hyperchromic shift (see Chapter 10), indicating secondary structure. Its sequence was determined to be

5'-AGGCGCCGACUCUACU-3'

If the molecule were an internal part of a message, what amino acid sequence would result from it following translation? (Refer to the code chart in Figure 13.7.)
Multiple Choice
Which of the following characteristics does NOT describe the triplet codon code?
Multiple Choice
Which of the following codons is a start codon?
Multiple Choice
Which of the following were used to discover the triplet code?
Open Question
In this chapter, we focused on the genetic code and the transcription of genetic information stored in DNA into complementary RNA molecules. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:How were the experimentally derived triplet codon assignments verified in studies using bacteriophage MS2?
Open Question
In this chapter, we focused on the genetic code and the transcription of genetic information stored in DNA into complementary RNA molecules. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:How were the specific sequences of triplet codes determined experimentally?
Open Question
In this chapter, we focused on the genetic code and the transcription of genetic information stored in DNA into complementary RNA molecules. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:What experimental evidence provided the initial insights into the compositions of codons encoding specific amino acids?
Open Question
In this chapter, we focused on the genetic code and the transcription of genetic information stored in DNA into complementary RNA molecules. Along the way, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions:Why did geneticists believe, even before direct experimental evidence was obtained, that the genetic code would turn out to be composed of triplet sequences and be nonoverlapping? Experimentally, how were these suppositions shown to be correct?