Concept explainers
Interpretation:
The amino acids those have most codons and least codons; reason for multiple codons for certain amino acids has to be interpreted.
Concept Introduction:
Codon: A sequence of three ribonucleotides in the mRNA chain that codes for a specific amino acid; also a three-
Genetic code: The sequence of nucleotides, coded in triplets (codons) in mRNA that determines the sequence of amino acids in protein synthesis.
Translation: A tRNA molecule is a single polynucleotide chain held together by regions of base pairing in a partially helical structure. An amino acid is bonded to its specific tRNA by an ester linkage. Connecting specific amino acid at end of the tRNA is known as charging tRNA. Once done, tRNA is ready to be used in the protein synthesis.
At the other end of the tRNA, three anticodons are present which are complementary to the codons present in mRNA. Once the anticodons pairs off with codons, the amino acid at terminal end of the tRNA is delivered and attached to the growing protein chain.
Illustrated relationships are:
DNA informational strand: 5’ ATG CCA GTA GGC CAC TTG TCA 3’
DNA Template strand: 3’ TAC GGT CAT CCG GTG AAC AGT 5’
mRNA: 5’ AUG CCA GUA GGC CAC UUG UCA 3’
protein: Met Pro Val Gly His Leu Ser
Notice: 5’ end of the mRNA strand codes for the N-terminal amino acid, whereas the 3’ end of the mRNA strand codes for the C-terminal amino acid. Proteins are always written N-terminal to C-terminal, reading left to right.
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Fundamentals of General, Organic, and Biological Chemistry (Principles of Chemistry - CHEM 1121)
- What is the start codon? What are the stop codons? Do any of them code for amino acids?arrow_forwardIn the gene-coding sequence shown here, which of the following events will produce a frameshift after the last mutational site? a. insertion of an A after the first codon b. deletion of the second codon (AAA) c. insertion of TA after the second codon and deletion of CG in the fourth codon d. deletion of AC in the third codonarrow_forwardA certain mRNA strand has the following nucleotide sequence: 5AUGACGUAUAACUUU3 What is the anticodon for each codon? What is the amino acid sequence of the polypeptide? (Use Figure 13-5 to help answer this question.) Figure 13-5 The genetic code The genetic code specifies all possible combinations of the three bases that compose codons in mRNA. Of the 64 possible codons, 61 specify amino acids (see Figure 3-17 for an explanation of abbreviations). The codon AUG specifies the amino acid methionine and also signals the ribosome to initiate translation (start). Three codonsUAA, UGA, and UAGdo not specify amino acids; they terminate polypeptide synthesis (stop).arrow_forward
- If an extra nucleotide is inserted in the first exon of the beta globin gene, what effect will it have on the amino acid sequence of the globin polypeptides? Will the globin most likely be fully functional, partly functional, or nonfunctional? Why?arrow_forwardIf the genetic code used 4 bases at a time, how many amino acids could be encoded?arrow_forwardIf the coding region of a gene (the exons) contains 2,100 base pairs of DNA, would a missense mutation cause a protein to be shorter, longer, or the same length as the normal 700 amino acid proteins? What would be the effect of a nonsense mutation? A sense mutation?arrow_forward
- In how many cases in the genetic code would it NOT be possible to know the amino acid specified by a codon if only the first two nucleotides of the codon are known?arrow_forwardWhat is the DNA sequence that encodes the codon AAG, with 5’ and 3’ ends labeled?arrow_forwardWhat are the amino acid coded for each of these codons? 1. UUA 2. AUU 3. UGU 4. AAA 5. GAG 6. UAAarrow_forward
- What is the first amino acid in the polypeptide? _____________________ A group of 3 nucleotides codes for one amino acid. How many codons are needed to make the polypeptide that results? _________ What is the resulting polypeptide: _______________________________________________________?arrow_forwardIf there are 64 codons, how can there be fewer than 64 tRNA molecules?arrow_forwardWhat is the initiator codon in both prokaryotres and eukaryotes? What amino acid is specified by this codon? UAA, methionine UAA or UGA; Arginine AUG; arginine AUG; methioninearrow_forward
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