The question asks about the specific scientific discovery for which Victor Ambros and Gary Ruvkun were awarded the Nobel Prize in Medicine.

Understanding the Nobel Prize in Medicine Discovery

The Nobel Prize in Physiology or Medicine is one of the most prestigious awards recognizing groundbreaking discoveries in the life sciences and medicine. In 2006, this esteemed prize was jointly awarded to Victor Ambros and Gary Ruvkun.

Analysis of the Correct Discovery

Based on the Nobel Prize information, Victor Ambros and Gary Ruvkun received the 2006 Nobel Prize in Physiology or Medicine for their discovery of microRNAs and their role in post-transcriptional gene regulation. MicroRNAs (miRNAs) are small, non-coding RNA molecules that play crucial roles in regulating gene expression. Their discovery revolutionized our understanding of how genes are controlled within cells.

Let's examine the options provided:

• Expression Sequence Tags (ESTs): ESTs are short sequences of cDNA used for gene discovery and gene mapping. While important in genomics, the Nobel Prize to Ambros and Ruvkun was not for ESTs.
• Micro RNA: This refers to microRNAs, which are small RNA molecules that regulate gene expression. This aligns with the discovery made by Victor Ambros and Gary Ruvkun.
• DNA micro array: DNA microarrays (or gene chips) are tools used to measure the expression levels of large numbers of genes simultaneously. This is a technology, not the specific molecular discovery made by Ambros and Ruvkun.
• SNP's: SNPs (Single Nucleotide Polymorphisms) are variations at a single position in a DNA sequence among individuals. Studying SNPs is important in genetics, but it is not the discovery for which Ambros and Ruvkun received the Nobel Prize.

Therefore, the discovery of Micro RNA is the correct answer.

Significance of Micro RNA Discovery

The discovery of microRNAs revealed a previously unknown mechanism of gene regulation. It showed that small RNA molecules can silence genes or reduce the production of proteins from messenger RNA (mRNA). This process, known as RNA interference (RNAi) or post-transcriptional gene silencing, is fundamental in various biological processes, including development, cell differentiation, and disease.

Revision Table: Key Concepts

Additional Information on Gene Regulation and RNA

Gene regulation is a complex process ensuring that genes are expressed at the right time and in the right place. It occurs at multiple levels, from transcription (DNA to RNA) to translation (RNA to protein) and post-translational modifications. MicroRNAs represent a key layer of post-transcriptional regulation.

Types of RNA involved in gene expression:

• Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes for protein synthesis.
• Transfer RNA (tRNA): Involved in protein synthesis by carrying amino acids to the ribosome.
• Ribosomal RNA (rRNA): A structural component of ribosomes.
• Small Non-coding RNAs: Includes miRNAs, small interfering RNAs (siRNAs), and others, involved in regulating gene expression.

The work by Ambros and Ruvkun, initially in the nematode C. elegans, identified the first microRNA, called lin-4, which regulated the expression of another gene, lin-14, through a mechanism involving RNA.