How do we know that the initial transcript of a eukaryotic gene contains noncoding sequences that must be removed before accurate translation into proteins can occur?

Verified step by step guidance

Understand that the initial transcript of a eukaryotic gene is called the primary RNA transcript or pre-mRNA, which includes both coding and noncoding sequences.

Recognize that noncoding sequences in the pre-mRNA are called introns, while the coding sequences are called exons.

Learn that experimental evidence, such as comparing the nucleotide sequence of the DNA gene with the sequence of the mature mRNA, shows that some sequences present in the DNA and pre-mRNA are missing in the mature mRNA, indicating removal of introns.

Know that techniques like RNA sequencing and hybridization experiments demonstrate that introns are spliced out during RNA processing before translation.

Understand that the presence of introns and their removal by splicing is essential for producing a continuous coding sequence in the mature mRNA, which can then be accurately translated into a functional protein.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Eukaryotic Gene Structure

Eukaryotic genes are composed of coding regions called exons and noncoding regions called introns. The initial RNA transcript, or pre-mRNA, includes both exons and introns, meaning it contains sequences that do not code for proteins and must be processed before translation.

RNA Splicing

RNA splicing is the process by which introns are removed from the pre-mRNA transcript and exons are joined together. This modification produces a mature mRNA that accurately reflects the protein-coding sequence, ensuring correct translation into functional proteins.

Experimental Evidence from Molecular Biology

Techniques such as comparing DNA and mature mRNA sequences, and observing RNA processing intermediates, have shown that initial transcripts contain extra sequences. Experiments like Northern blotting and cDNA cloning reveal that introns are present in the primary transcript but absent in mature mRNA.

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How were the specific sequences of triplet codes determined experimentally?

How were the experimentally derived triplet codon assignments verified in studies using bacteriophage MS2?

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Write a short essay that summarizes the key properties of the genetic code and the process by which RNA is transcribed on a DNA template.

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Textbook Question

Assuming the genetic code is a triplet, what effect would the addition or loss of two nucleotides have on the reading frame? The addition or loss of three, six, or nine nucleotides?

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Textbook Question

The mRNA formed from the repeating tetranucleotide UUAC incorporates only three amino acids, but the use of UAUC incorporates four amino acids. Why?

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