Messenger RNA (mRNA)

Definition

Messenger RNA (mRNA) is a single-stranded nucleic acid that carries genetic information from DNA to the ribosome, where proteins are synthesized. It plays a critical role in gene expression by serving as the template for translating the genetic code into a corresponding sequence of amino acids, ultimately forming proteins essential for cellular function.

5 Must Know Facts For Your Next Test

1. mRNA is synthesized during transcription, where RNA polymerase reads the DNA template and produces a complementary mRNA strand.
2. Once synthesized, mRNA undergoes processing, including the addition of a 5' cap and a poly-A tail, which protect it from degradation and help in translation.
3. The sequence of nucleotides in mRNA corresponds to specific codons that dictate which amino acids are added during protein synthesis.
4. mRNA can have different lifespans in the cell, influencing how much protein can be produced from it, which is regulated by factors like degradation rates and translational efficiency.
5. In eukaryotic cells, mRNA is exported from the nucleus to the cytoplasm, where it can be translated into proteins by ribosomes.

Review Questions

• How does mRNA serve as a link between DNA and protein synthesis?
  • mRNA acts as a bridge between DNA and protein synthesis by carrying the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm. During transcription, a specific gene's DNA sequence is transcribed into mRNA. This mRNA then provides the template that ribosomes use to translate the sequence into a specific protein, with each set of three nucleotides (codons) corresponding to an amino acid.
• Discuss the processing steps that mRNA undergoes after transcription and their importance in gene expression.
  • After transcription, mRNA undergoes several processing steps that include the addition of a 5' cap and a poly-A tail. The 5' cap protects mRNA from degradation and aids in ribosome recognition during translation, while the poly-A tail increases stability and facilitates transport out of the nucleus. These modifications are crucial because they enhance mRNA's ability to be translated efficiently into protein and ensure its stability within the cell.
• Evaluate how variations in mRNA expression levels can impact cellular function and overall organism health.
  • Variations in mRNA expression levels can significantly impact cellular function by influencing protein production. High levels of certain mRNAs can lead to increased synthesis of specific proteins necessary for various cellular activities, while low levels can result in insufficient protein production, affecting processes such as metabolism, growth, and response to stress. Disruptions in this balance can contribute to diseases such as cancer or genetic disorders, highlighting the importance of tight regulation of mRNA levels for maintaining overall organism health.

Related terms

DNA: Deoxyribonucleic acid (DNA) is the molecule that contains the genetic blueprint for all living organisms, consisting of two strands that form a double helix.

Ribosome:

A ribosome is a cellular structure made of ribosomal RNA (rRNA) and proteins, where the translation of mRNA into protein occurs.

Transcription:

Transcription is the process of copying a segment of DNA into mRNA, which is the first step in gene expression.