C) Most of the mutations that Yanofsky recovered were missense mutations However
ID: 205281 • Letter: C
Question
C) Most of the mutations that Yanofsky recovered were missense mutations However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein? Why or why not? 3. What does it mean that the genetic code is degenerate? 4.In eukaryotes and prokaryotes, what is the sequence of the initiator codon? 5. Nirenberg and Matthaei as well as Khorana were able to synthesize RNA molecules with repeating sets of nucleotides of various lengths and then analyze the amino acid sequence of the proteins that were encoded by these molecules. So for instance, RNA molecules of repeating single nucleotides such as U to give UUUU... or A to give AAAAA... These give rise to single repeating amino acids. Repeating dinucleotides such as UC to give UCUCUCUC.. .These give rise to repeating units of 2 amino acids (Ser, Leu). Imagine that you carried out this experiment and made 9 RNA types composed of the following repeated sequences GUA.. GUAC.. GUACC GUACCG How many amino acids do you expect to make up a repeating unit in the polypeptides produced from these RNAs? How could this experiment be used to support the hypothesis that the genetic code uses a triplet code?Explanation / Answer
Answer 3
In the genetic code, three nucleotides code for one amino acid. With four nucleotides, there are 64 possible combinations of three nucleotides. Each is called a codon.However, only 20 different amino acids are used to make proteins. Since every codon must be used for something to have a working code, this means that at least some of the amino acids must have multiple codons. The term "degenerate" simply refers to the fact that the translation from nucleotide codons to amino acids isn't one to one. Some parts of the genetic code are redundant.
Answer 4
AUG
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