BPS 3101 Lecture Notes - Lecture 2: Stop Codon, Start Codon, Intron
Document Summary
Dna double helix: minor and major grooves, sugar-phosphate backbone, antiparallel dna strands, hydrogen bonds between bases. Intron non-coding sequences removed from pre-rna (by splicing: exon sequences that remain in mature rna, first exon will have the 5"utr, last exon will have the 3"utr. Introns can be in utr regions: gene from c-d-e. Include the introns start codon to the end codon: structural gene, exons c-e, intron d, translation initiation site b/c junction, translation termination site e/f junction, transcription initiation site a/b junction, promoter upstream of a/b junction. Human genes: intron length: typically, 200 nt to >10 kb, number per gene: several to dozens, exon length: typically, 100 to 200 nt. Plant genes: intron density similar to animals, but shorter, 100 300 nt. Yeast genes: <5% of yeast genes have introns (vs. >95% of genes have introns in mammals, mostly trna genes (intron length 20-30 nt) and in ribosomal protein genes (intron length 100-500 nt)