BSC 315 Lecture Notes - Lecture 11: Cistron, Start Codon, Gene Expression
23 Mar 2016
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A segment of a dna molecule that is transcribed into an rna, & the sequences that control its transcription (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) Ribosome reads mrna 3 nucleotides at a time, beginning w/ aug (met) codon closest to 5" end. Note that parts of the mrna at each end are not translated. Each of these parts can be identified in the gene itself. Translated region & the 5"utr & 3" utr. Transcription is regulated by promoters & other regulatory sequences. Promoter- just upstream from transcribed region: generally not transcribed. Enhancers- regulate timing/cell type/circumstances of transcription: not transcribed. Transcription terminator- part of primary transcript (cid:1) (cid:1) (cid:1) One gene can produce several (or many) different mrnas by alternative splicing (cid:1) (cid:1) (cid:1) (cid:1) (cid:1) Alternative splicing- mrnas contain different combinations of exons. Eukaryotic genes have one protein coding region per mrna.
