Question

Alternative splicing of exons results in a. posttranslational modifications of proteins. b. the production of different mRNA molecules from a common precursor RNA molecule. c. the production of siRNA and RNA silencing. d. the production of a genome that is larger than the proteome.

Short answer

The correct answer is b. The production of different mRNA molecules from a common precursor RNA molecule, as alternative splicing of exons rearranges exons within a pre-mRNA molecule to generate different mRNA molecules that will be translated into different protein products.

Step-by-step solution

1. Understand the concept of alternative splicing

Alternative splicing is a process that occurs during gene expression, which allows a single gene to produce multiple proteins. In this process, the exons (protein-coding regions) of a pre-mRNA molecule are rearranged by being either included in or excluded from the final mRNA molecule that will be translated into a protein. As a result, one gene can give rise to several proteins with different functions.

2. Analyze the given options

Once you understand the concept of alternative splicing, you can now analyze the given options in the exercise: a. Posttranslational modifications of proteins: These are chemical modifications that occur after the protein has been translated from the mRNA. While important for protein function, this process does not directly relate to alternative splicing. b. The production of different mRNA molecules from a common precursor RNA molecule: This option indeed describes the alternative splicing process, where the exons of a pre-mRNA molecule are rearranged to produce different mRNA molecules, which are later translated into different proteins. c. The production of siRNA and RNA silencing: siRNA (small interfering RNA) and RNA silencing are mechanisms involved in the regulation of gene expression but are not directly related to alternative splicing. d. The production of a genome that is larger than the proteome: This option does not make sense because the genome refers to the complete set of genetic material, while the proteome refers to the entire set of proteins expressed by an organism. These two terms are not directly comparable in size, and this option does not relate to alternative splicing.

Select the correct option

Based on the analysis of the given options, the correct choice is: b. The production of different mRNA molecules from a common precursor RNA molecule. This is because alternative splicing results in the rearrangement of exons within a pre-mRNA molecule, thereby generating different mRNA molecules that will be translated into different protein products.

Key concepts

Gene Expression

Gene expression is the amazing process by which our genes' information is used to make functional products like proteins. Think of it as the blueprint turning into action. The journey starts in the nucleus of the cell, where the information in a gene is copied from DNA to mRNA in a process called transcription.

The mRNA, a kind of messenger, then travels out of the nucleus into the cytoplasm. At this stage, mRNA carries the genetic code that will be used to make proteins. But this process is not just "copy and paste"—it's more like tailoring. Certain parts of the genetic code can be turned on or off, which means genes can be expressed in different ways, in different tissues, or at different times.

• This explains why hair cells differ from liver cells, even though both contain the same DNA.
• Gene expression can be influenced by signals from the environment, and it allows cells to respond smartly to their surroundings.

Alternative splicing is one of the mechanisms that contributes to the diversity of proteins and plays a crucial role during gene expression. It enables a single gene to produce multiple proteins, adding complexity to how genes translate into traits.

pre-mRNA

Pre-mRNA, or precursor mRNA, is an initial form that RNA takes right after transcription. It is a rough draft of the messenger RNA (mRNA) that will eventually be translated into proteins. However, at this point, pre-mRNA is still raw and unprocessed, featuring a mix of coding regions known as exons and non-coding regions known as introns.

To become a mature mRNA, certain modifications occur.

• The non-coding introns are removed in a process called splicing.
• The exons, which are the sequences that code for proteins, are connected together.

Alternative splicing happens during this stage. It is when the cell selects different combinations of exons to include in the final mRNA. This allows a single pre-mRNA to give rise to multiple unique mRNA variants, and consequently, different protein products.

Protein Synthesis

Protein synthesis is the process of turning the mRNA code into a chain of amino acids, forming proteins, which are the building blocks and workhorses of the cell. This process happens in two main stages: translation and folding.

• During translation, the mRNA sequence is read by the ribosome, a kind of molecular machine that assembles amino acids in the correct order based on the mRNA code.
• Each three-nucleotide sequence on the mRNA, known as a codon, specifies a particular amino acid.

Once the chain is complete, it folds into a specific three-dimensional structure that is essential for its function. A properly folded protein can then perform functions that are critical to life, from regulating cell processes to protecting the body from pathogens.

Alternative splicing allows for the production of different proteins from the same gene, enabling organisms to perform a wider array of functions and adapt to environmental changes more efficiently. This diversity is why alternative splicing is so important in protein synthesis, permitting a broader range of protein functions and contributing to the complexity of life.