Question

What does a polycistronic mRNA do? A. It contains a large number of cytosine bases. B. It is translated to a protein that contains many cysteine amino acids. C. It codes for more than one polypeptide . D. It is translated to a protein involved in polycystic fibrosis.

Short answer

C. It codes for more than one polypeptide.

Step-by-step solution

Understanding mRNA

Messenger RNA (mRNA) is a type of RNA that conveys genetic information from DNA to the ribosome, where proteins are synthesized.

Polycistronic mRNA Concept

Polycistronic mRNA is a single mRNA molecule that can encode multiple polypeptide chains. This means it can be translated into multiple proteins.

Comparing the Options

Option A discusses cytosine bases, which is unrelated to encoding multiple polypeptides. Option B mentions cysteine amino acids, which is also not specific to polycistronic mRNA. Option D refers to polycystic fibrosis, a condition not related to the structure of mRNA. Option C states that polycistronic mRNA codes for more than one polypeptide, which fits the definition.

Conclusion

Given the definition and analysis, the correct answer is the option that aligns with polycistronic mRNA's ability to code for multiple proteins.

Key concepts

Understanding mRNA

Messenger RNA (mRNA) plays a crucial role in the process of converting genetic information from DNA to proteins. It acts as a mediator, carrying the genetic code from a cell's DNA to its ribosome, where protein synthesis occurs.
This journey begins in the nucleus, where DNA is transcribed into a complementary mRNA sequence. This mRNA sequence then travels to the cytoplasm.

At the ribosome, the mRNA is read in sets of three bases known as codons, each coding for a specific amino acid. The ribosome assembles these amino acids into polypeptide chains, which then fold into functional proteins.

Thus, mRNA forms the bridge between our genetic blueprints and the functional proteins that perform essential biological tasks.

What is Genetic Coding?

Genetic coding is the process through which information from the genetic code in DNA is translated into functional proteins. This is achieved via the sequence of nucleotides in mRNA. Each sequence of three nucleotides, called a codon, corresponds to one specific amino acid or a stop signal during protein synthesis.

This genetic code is almost universal, shared by nearly all organisms, from the smallest bacteria to humans. Understanding genetic coding is fundamental to biology since it dictates how proteins are formed, and proteins are crucial for almost every cellular function.

The elegance of this system lies in its simplicity and consistency. With only four bases (adenine, uracil, cytosine, and guanine) forming 64 possible codons, this redundancy ensures that even some genetic mutations do not alter the protein being produced.

Polypeptides Explained

Polypeptides are chains of amino acids linked together by peptide bonds. These chains fold into specific three-dimensional structures to form proteins. The sequence and the properties of the amino acids determine the final structure and function of the protein.

Polypeptides are crucial because they form the ultimate building blocks of proteins that are involved in virtually all cellular processes. For example:

• Enzymes, which catalyze biochemical reactions
• Structural proteins, which provide support and shape to cells and tissues
• Transport proteins, which move molecules across cell membranes

In the context of polycistronic mRNAs, the mRNA molecule can encode more than one polypeptide, resulting in multiple proteins being synthesized from a single mRNA transcript. This is common in prokaryotes and allows efficient use of genetic information.