Question

The \(\alpha\) chain of eukaryotic hemoglobin is composed of 141 amino acids. What is the minimum number of nucleotides in an mRNA coding for this polypeptide chain?

Short answer

Answer: The minimum number of nucleotides required to code for a polypeptide chain composed of 141 amino acids is 423.

Step-by-step solution

Understanding the relationship between nucleotides, codons, and amino acids

Amino acids are the building blocks of proteins. They are encoded in the DNA by a sequence of three nucleotides called a codon. Each codon corresponds to one specific amino acid. In an mRNA molecule, this coding is retained and is subsequently used during translation to synthesize the protein.

Calculate the minimum number of nucleotides for the given number of amino acids

We are given the number of amino acids in the α chain of eukaryotic hemoglobin (141 amino acids). Since each amino acid is coded by a codon, and each codon consists of 3 nucleotides, we can find the minimum number of nucleotides required by multiplying the number of amino acids by the number of nucleotides per codon. Minimum number of nucleotides = (Number of amino acids) * (Number of nucleotides per codon) Minimum number of nucleotides = 141 * 3

Find the answer

Now, we just need to do the calculation to find the minimum number of nucleotides. Minimum number of nucleotides = 141 * 3 = 423 So, the minimum number of nucleotides in an mRNA coding for this polypeptide chain is 423.

Key concepts

Codons

In genetics, codons are sequences of three nucleotides that act as a code for specific amino acids. Consider codons as the alphabet of genetic instruction. Each triplet of nucleotides forms a unique codon. There are four possible nucleotide bases: Adenine (A), Cytosine (C), Guanine (G), and Uracil (U) in mRNA.

• Codons are fundamental units in the genetic code.
• Each codon specifies one of the 20 different amino acids.
• With three nucleotides per codon, there are 64 possible codon combinations (4^3).

These codons ensure that the genetic code is both robust and versatile. In the process of creating proteins, codons play a crucial role, as they determine the order of amino acids in the protein chains.

Amino Acids

Amino acids are organic compounds that combine to form proteins. Often referred to as the building blocks of life, they contain an amino group, a carboxyl group, and a unique side chain. Proteins, which are essential for nearly every function within an organism, are composed of chains of these amino acids.

• There are 20 standard amino acids that cells use to build proteins.
• Amino acids are arranged in chains linked by peptide bonds.
• The sequence and number of amino acids determine a protein's structure and function.

Each amino acid is encoded by one or more codons, showcasing the redundancy built into the genetic code. This redundancy is crucial during DNA replication and mRNA translation, minimizing errors in protein synthesis.

mRNA Translation

Translation is the stage of gene expression where mRNA is decoded to produce a specific protein. This process occurs in the ribosome, which is the cellular machine responsible for reading mRNA and assembling protein chains. During translation, each codon in the mRNA is matched with its corresponding amino acid.

• The ribosome moves along the mRNA strand, interpreting each codon.
• Amino acids are brought to the ribosome by transfer RNA (tRNA).
• Each tRNA has an anticodon that pairs with its corresponding codon on the mRNA.
• Once the amino acids are positioned, they bind together, forming a polypeptide chain.

Eventually, the chain folds into a specific shape, becoming a functioning protein. The process of mRNA translation exemplifies the central dogma of biology, where genetic information flows from DNA to RNA to protein, driving cellular activity and organism traits.