The genetic code is thought to have evolved to maximize genetic stability by minimizing the effect on protein function of most substitution mutations (single-base changes). We will use the six arginine codons to test this idea. Consider all of the substitutions that could affect all of the six arginine codons.(a) How many total mutations are possible?(b) How many of these mutations are “silent,” in the sense that the mutantcodon is changed to another Arg codon?(c) How many of these mutations are conservative, in the sense that an Argcodon is changed to a functionally similar Lys codon?

A 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).

Consequences of the Wobble Hypothesis Point out why Cricks wobble hypothesis would allow fewer than 61 anticodons to be used to translate the 61 sense codons. How might wobble tend to accelerate the rate of translation?

If the genetic code uses triplets, how many different amino acids can be coded by a repeating RNA polymer composed of UA and UC (UAUCUAUCUAUC ...)? a. one b. two c. three d. four e. five

In 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 codon

What percentage of the DNA in the genome actually corresponds to genes? How much is actually protein-coding exons? What makes up the rest?

What is the start codon? What are the stop codons? Do any of them code for amino acids?

Given the following tRNA anticodon sequence, derive the mRNA and the DNA template strand. Also, write out the amino acid sequence of the protein encoded by this message. tRNA: UAC UCU CGA GGC mRNA: protein: How many hydrogen bonds would be present in the DNA segment?

State the properties of the WatsonCrick model of DNA in the following categories: a. number of polynucleotide chains b. polarity (running in same direction or opposite directions) c. bases on interior or exterior of molecule d. sugar/phosphate on interior or exterior of molecule e. which bases pair with which f. right- or left-handed helix

IS. Alternative splicing has been estimated to occur in more than 95% of multi-exon genes. Which of the following is not an evolutionary advantage of alternative splicing? Alternative splicing increases diversity without increasing genome size Different gene isoforms can be expressed in different tissues Alternative splicing creates shorter mRNA transcripts Different gene isoforms can be expressed during different stages of development.