Question

A genetic code in which two bases encode a single amino acid is not adequate for protein synthesis, Give a reason why.

Short answer

Two-base codons provide only 16 combinations, which is insufficient to encode all 20 amino acids required for protein synthesis.

Step-by-step solution

- Understand Genetic Coding

Genetic coding is the process by which the information in DNA is used to produce proteins. DNA sequences are read in sets of three nucleotides called codons, with each codon encoding a specific amino acid. This triplet system ensures there are enough unique codons (64 possible combinations) to encode all 20 amino acids.

- Calculate Two-Base Combinations

If only two nucleotide bases were used to encode each amino acid, calculate the possible combinations. Since DNA has four nucleotide bases (adenine, cytosine, guanine, and thymine), the number of different codons that could be formed by two bases is 4^2, or 16.

- Compare Possible Codons with Required Amino Acids

There are 20 standard amino acids that must be encoded by the genetic code. Compare this number with the 16 possible two-base codons. Since 16 is less than 20, a two-base codon system would not provide enough unique codons to encode all 20 amino acids required for protein synthesis.

- Conclusion

A genetic code in which two bases encode each amino acid is not adequate for protein synthesis because it allows for a maximum of 16 unique codons, which is insufficient to encode all 20 standard amino acids.

Key concepts

Understanding Codons

The term 'codons' refers to sequences of three nucleotide bases in DNA or RNA. These triplets are read during the process of protein synthesis. Each of the 64 possible codons maps to a specific amino acid or a stop signal. The redundancy in the genetic code allows for some codons to encode the same amino acid, ensuring that the genetic instructions are accurately translated. The importance of codons can be seen in how they ensure the diversity of protein structures necessary for the body to function properly.

Protein Synthesis Process

Protein synthesis is a vital biological process where cells create proteins. It involves two main stages: transcription and translation.

1. **Transcription**: The DNA sequence of a gene is copied to make an RNA molecule. This RNA strand carries the genetic information from the DNA in the nucleus to the ribosome in the cytoplasm.
2. **Translation**: The RNA is read by the ribosome in sets of three bases, known as codons. Each codon matches a specific amino acid, which are then linked together to form a protein.

These steps ensure that genetic instructions are converted into functional proteins, which are necessary for various cellular functions.

Amino Acids: Building Blocks of Proteins

Amino acids are organic compounds that combine to form proteins. They are often referred to as the building blocks of life.

In the genetic code, each amino acid is encoded by one or more codons. There are 20 standard amino acids, each with unique properties that influence protein structure and function. Without a sufficient number of unique codons, not all amino acids could be distinctly encoded, leading to potential issues in protein synthesis and function.

The variety and specific sequence of amino acids in a protein determine its structure and function, which are crucial for the myriad roles proteins play in the body.

Nucleotide Bases: The Alphabet of DNA

The term 'nucleotide bases' refers to the four chemical subunits that make up DNA: adenine (A), cytosine (C), guanine (G), and thymine (T). These bases pair in specific ways: A pairs with T, and C pairs with G. The sequence of these bases in DNA determines the genetic code.

During protein synthesis, the sequence of nucleotide bases is read in sets of three, or codons, which then specify amino acids. This process allows for the translation of genetic information from DNA to functional proteins, ensuring that cells operate correctly and efficiently.

Role of DNA in Genetic Coding

DNA, or deoxyribonucleic acid, is the molecule that carries the genetic instructions for life. DNA's structure is a double helix made up of two strands of nucleotide bases. The sequence of these bases encodes genetic information.

The process of genetic coding involves transcribing DNA sequences into RNA, which then translates these sequences into proteins. These proteins carry out various critical functions in the body, from enzyme activity to structural support. Therefore, the integrity and expression of DNA are crucial for proper cellular function and overall organism health.