Läsram

Läsram, in genetics, refers to the reading frame—the way a nucleotide sequence is partitioned into consecutive codons of three nucleotides for translation into protein. Because codons are triplets, each DNA or RNA strand has three potential reading frames in the forward direction and three in the reverse complement, for a total of six possible frames. The frame used by the cellular machinery is typically determined by the location of regulatory signals and the start codon.

A central concept related to läsram is the open reading frame (ORF). An ORF is a continuous stretch of nucleotides that begins with a start codon and ends with a stop codon, without any in-frame stop codons in between. In practice, several potential frames may contain start and stop codons, but only those corresponding to plausible, long enough coding sequences are considered strong candidates for protein-coding genes. In prokaryotes, genes often align with a single ORF, while in eukaryotes, genes may be interrupted by introns and undergo splicing before the reading frame is established in mature mRNA.

Frameshift mutations—insertions or deletions not in multiples of three—alter the reading frame downstream and typically disrupt the resulting protein. Correctly identifying the reading frame is essential for gene annotation, protein prediction, and comparative genomics. Bioinformatic tools scan genomic sequences for ORFs, start and stop signals, and other features to infer the most likely reading frames and annotate coding regions. Understanding läsram is fundamental to studying gene structure and translational biology.