Most amino acids are coded for by a set of similar codons (see Figure17.6). Propose at least one evolutionary explanation to account for this pattern.

Short Answer

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The amino acids are coded with a similar set of codons. Codon is the three-nucleotide sequence that is present in the DNA that can produce an amino acid.

Three different types of theories that deal with the origin and evolution of the codon are stereochemical theory, coevolution theory, and error minimization theory.

Step by step solution

01

Amino acids

Amino acids are the basic building block of the protein encoded in the DNA. These amino acids are produced out of genetic code that corresponds to a particular amino acid.

02

Stereochemical theory

There exists physicochemical affinity between the amino acids’ codon and nucleotide triplets. The physical property is an essential reason for the repetitions of the amino acid codon that codes for a particular amino acid.

03

Coevolution theory

According to this theory, the amino acid biosynthesis pathway is responsible for the amino acids codon arrangement. The gene is another controlling factor that can determine the similar codon responsible for coding particular amino acids.

04

Error minimization theory

The genetic code can minimize transcriptional as well as translational error. It reduces the randomization of amino acids. After minimization of randomization, the genetic code transfers into amino acids.

According to this theory, the similarity between amino acid codons results from a reduction in randomization.

Hence, the codons corresponding to amino acids arise out of three major evolutionary theories: stereochemical, coevolution, and error minimization.

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Most popular questions from this chapter

The height of a stack letters in a logo indicates the predictive power of the stack (determined statistically). If the stack is tall, we can be more confident in predicting what base will be in that position of a new sequence is added to the logo. For example, at position2 in the sequence alignment, all 10 sequences have a G: the probability of finding a G there in a new sequence is very high, as is the stack in the sequence logo. For short stacks, the bases all have about the same frequency, so it’s hard to predict would be at those positions. (a) Looking at the sequence logo, which two positions have the most predictable bases? What bases do you predict would be at those positions in a newly sequenced gene? (b) Which 12 positions have the least predictable bases? How do you know? How does this reflect the relative frequencies of the base shown at these positions in the sequence alignment? Use the two leftmost positions of the 12 as examples in your answer.

Draw a tRNA with the anticodon 3’-CGU-5’. What two different codons could it bind to? Draw each codon on an mRNA, labeling all 5’ and 3’ ends, the tRNA, and the amino acid it carries.

Evolution accounts for the unity and diversity of life, and the continuity of life is based on heritable information in the form of DNA. In a short essay (100-150words), discuss how the fidelity with which DNA is inherited is related to the processes of evolution. (Review the discussion of proofreading and DNA repair in Concept 16.2)

The template strand of a gene includes this sequence:

3’-TACTTGTCCGATATC-5’. It is mutated to

3’-TACTTGTCCAATATC-5’. For both wild-type and mutant sequences, draw the double-stranded DNA, the resulting mRNA, and the amino acid sequence each encodes. What is the effect of the mutation on the amino acid sequence?

Knowing that the genetic code is almost universal, a scientist uses molecular biological methods to insert the human β-globin gene(shown in Figure17.12) into bacterial cells, hoping the cell will express it and synthesize functional β-globin protein. Instead, the protein produced is non-functional and contains fewer amino acids than does β-globin made by a eukaryotic cell. Explain why.

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