Contents
What is the difference between intergenic DNA and introns?
The introns are stretch of noncoding DNA sequence between two successive exons. On the other hand, the genome of prokaryotes lacks introns in their genes. In contrast, intergenic regions do not encode protein and are poorly conserved in the genome.
Does RNA-seq detect introns?
RNA-seq datasets can contain millions of intron reads per library that are typically removed from downstream analysis. We demonstrate how intron reads can be utilized in differential expression analysis using our index method where a unique set of differentially expressed genes can be detected using intron counts.
Are intergenic regions conserved?
Intergenic regions are either highly conserved in sequence and length (Respirovirus, Henipavirus, Morbillivirus) or are not conserved in sequence and length (Rubulavirus, Avulavirus, Pneumovirinae).
Why do we have noncoding DNA?
However, it is becoming clear that at least some of it is integral to the function of cells, particularly the control of gene activity. For example, noncoding DNA contains sequences that act as regulatory elements, determining when and where genes are turned on and off.
What can intron retention cause?
(1999) suggested that retained introns can introduce a stop codon in an open reading frame or frameshift, which can contribute to gene expression regulation via premature termination of translation without changing the transcriptional activity.
Do intergenic regions get transcribed?
Intergenic regions are a subset of noncoding DNA. Occasionally some intergenic DNA acts to control genes nearby, but most of it has no currently known function. Recently transcribed RNA from the DNA fragments in intergenic regions were known as “dark matter” or “dark matter transcripts”.
Do bacteria have intergenic regions?
Nontranslated intergenic regions (IGRs) compose 10–15% of bacterial genomes, and contain many regulatory elements with key functions. Despite this, there are few systematic studies on the strength and direction of selection operating on IGRs in bacteria using whole-genome sequence data sets.
How many reads are mapped to intronic or exonic regions?
After the alignment step I checked the rnaseq metrics of all the samples. Among 40 samples three samples show high percentage of reads mapped to intronic regions. What could be the reason?
What are causes of reads mapped to intergenic region?
Intronic reads could be due to 1) immature transcripts with introns not spliced out yet 2) unannotated exons which might represent alternative splicing, if the sequence and mapping quality are reliable. Intronic reads could be due to intron-inclusion splice-variants. The quality of the cDNA library is also of concern.
Where do intronic reads of RNA come from?
The intronic reads likely originate from immature transcripts which include either full-length pre-mRNA molecules or nascent transcripts where the RNA polymerase has not yet attached to the 3′ end of the gene. A roughly equal distribution of reads mapping to intronic, exonic and intergenic regions suggests that there is DNA contamination.
What are the differences between intronic and exonic reads?
The differences in exonic (Δexon) and intronic (Δintron) read counts between experimental conditions are then quantified and compared to each other. ( b) Δexon and Δintron after treatment of human A549 cells with the glucocorticoid dexamethasone.