Part 1 Flashcards
(6 cards)
Look at the main differences in gene structure between eukaryotes and prokaryotes (exons/introns)
Introns present in most genes of complex eukaryotes.
- all genes encoding histones, so introns not required for gene function
Introns found rarely in prokaryotes, genome consists of entirely protein coding sequences.
Understand the functional/regulatory roles of introns
Many introns encode functional products, proteins or noncoding RNA (nested genes)
Introns contain regulatory sequences that control gene expression, regulate differences in gene expression determine differences between cells. Located at first intron.
What are nested genes?
One gene is contained within an intron of a larger gene. In humans less frequence some encode for pseudogene or noncoding RNAs.
Look at the role of ‘alternative splicing’ in extending the functional repertoire of the human genome
The presence of introns allows exons of genes to be joined in different combinations, and the synthesis of different proteins from the same gene. Occurs frequently in eukaryotes, 90% of human genes can be alternatively spliced to yield different mRNA
Understand the steps involved in repression of translation of mRNA BY miRNA – and specific roles of Drosha, Dicer and RISC
1)miRNA genes are transcribed to yield primary transcripts that contain hairpin structures
2) pri-mRNA are sequentially cleaved by the nuclease Drosha and dicer to yield double-stranded miRNA
3) miRNA associates with the RISC complex, in which two strands of miRNA are unwound.
4) miRNA then targets RISC to the 3’ untranslated region (UTR) of an mRNA leading to repression of translation and mRNA degradation
Understand the basic steps in RNA processing
Most eukaryotic genes contain segments of coding sequences (exons) interrupted by noncoding sequences (introns). Both exons and introns are transcribed to yield a long primary RNA transcript. Introns are removed by splicing to form the mature mRNA.
