A gene of a bacterium has 1200 base pairs on its coding strand, from the start codon ATG to the…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A gene of a bacterium has 1200 base pairs on its coding strand, from the start codon ATG to the last base of the stop codon TAA. The spacing of the base pairs is . Find the number of codons, the number of amino acids in the protein, the approximate molar mass of the protein and the length of the gene in nm. Take an average amino acid residue as , and add one water () for the two ends of the chain.
Need a reminder? The key ideaShow
In B-DNA the base pairs are apart and there are about base pairs in a turn. A codon is three bases, and a stop codon does not code for an amino acid. The mass fraction of an element in a molecule is .
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Codons. .
Step 2. Amino acids. The last codon, TAA, is a stop codon. So there are amino acids.
Step 3. Molar mass. .
Step 4. Length. .
Answer: 400 codons, 399 amino acids, about and .
Check. The protein is about 44 kg/mol, in the range of a typical enzyme.
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