Best writers. Best papers. Let professionals take care of your academic papers

Order a similar paper and get 15% discount on your first order with us
Use the following coupon "FIRST15"
ORDER NOW

Lab Exercise The genetic code is degenerate,

/in /by

Lab Exercise
The genetic code is degenerate, with two to six codons specifying each of the amino acids except for methionine and tryptophan. To explore this idea use the codon database and find data on the six leucine codons.

Go to the codon database complied from GenBank data: http://www.kazusa.jp/codon/ . Search Homo sapiens, Escherichia coli, Arabidopsis thaliana, and Caenorhabditis elegans in the query box. Answer each question fully.

1. Are all of the codons specifying a given amino acid used with equal frequency, or are some codons used more frequently than others? For example, the codons UUA, UUG, CUU, CUC, CUA, and CUG all specify leucine. Are these six leucine codons present with equal frequency in the coding regions of mRNAs?

2. Are the six codons specifying leucine used with equal frequency in mRNAs transcribed from human nuclear genes? From human mitochondrial genes? Are these codons used at the same frequency in nuclear and mitochondrial genes?

3. Are the leucine codons used at about the same frequencies in the four different species? Is there any bias in codon usage (preferred use of specific codons) related to the AT/GC content of the genomes of different species?

Lab Problems

The following DNA sequence occurs in the nontemplate strand of a structural gene in a bacterium (the promoter sequence is located to the left but is not shown):

5’-GAATGTCAGAACTGCCATGCTTCATATGAATAGACCTCTAG-3’

(a) What is the ribonucleotide sequence of the mRNA molecule that is transcribed from this piece of DNA?

(b) What is the amino acid sequence of the polypeptide encoded by this mRNA?

(c) If the nucleotide indicated by the red letter undergoes a mutation that changes T to A, what will be the resulting amino acid sequence following transcription and translation?

 
Looking for a Similar Assignment? Order now and Get 10% Discount! Use Coupon Code "Newclient"