Problem 70 - Chemistry A Molecular Approach

Question

A dimeric protein contains 142 amino acids in one strand and 148 in the other. How many codons code for these amino acids? How many nucleotides?

Step-by-Step Solution

Answer

There are 290 codons and 870 nucleotides coding for the amino acids in the dimeric protein.

Step 1: Determine the Total Number of Amino Acids

To find the total amount of amino acids in the dimeric protein, add the number of amino acids in one strand to the number in the other strand.

Step 2: Calculate the Number of Codons

Since each amino acid is coded by one codon, the total number of codons is equal to the total number of amino acids.

Step 3: Determine the Total Number of Nucleotides

Every codon is made up of three nucleotides. Therefore, multiply the total number of codons by three to get the total number of nucleotides.

Key Concepts

Amino Acids

Amino acids are the building blocks of proteins, which are crucial biomolecules in all living organisms. Proteins themselves are composed of long chains of amino acids that fold into complex three-dimensional structures to perform various functions in the body. There are 20 standard amino acids that make up the bulk of proteins, each with unique chemical properties.

In the context of our exercise, understanding amino acids is essential for grasping how proteins are synthesized. The number of amino acids in a polypeptide chain—in this case, two chains of a dimeric protein—directly relates to the length and function of the resulting protein. The primary structure of proteins is the sequence of amino acids, which ultimately determines the protein's shape and function following folding.

Nucleotide Number Determination

To understand nucleotide number determination, it's crucial to recognize that nucleotides are the basic structural units of nucleic acids like DNA and RNA. In the realm of genetics, these molecules carry the genetic blueprint in the form of sequences known as codons. Each codon consists of three nucleotides and encodes for a specific amino acid.

As highlighted in the exercise, the total number of nucleotides can be derived from the quantity of codons which in turn corresponds to the number of amino acids. To illustrate, assuming a dimeric protein with two strands, one with 142 amino acids and the other with 148, the combined total of amino acids is 290. Since each amino acid is represented by a single codon, we also have 290 codons. Calculating the number of nucleotides then becomes a multiplication process: 290 codons times three nucleotides per codon gives us 870 nucleotides.

Genetic Code

The genetic code is a set of rules by which information encoded in genetic material (DNA or mRNA sequences) is translated into proteins by living cells. It is essentially the language that instructs the synthesis of proteins through the process known as translation. The code is universal among most organisms and consists of codons, which are triplets of nucleotides.

Each codon specifies a particular amino acid, allowing for the assembly of amino acids in the proper order to form a protein. For instance, the codon AUG not only serves as the start signal for protein synthesis but also codes for the amino acid methionine. Through the genetic code, a specific sequence of nucleotides in DNA can be transcribed into mRNA and then read in sets of three nucleotides to create polypeptide chains, leading to the formation of proteins.