Chap 6+7 - Initiating transcription + Control of gene expression Flashcards
Basic genetic mechanisms: how cells read the genome: from DNA to protein, control og gene expression
Name the different RNA polymerases and what they synthesize.
RNA polymerase I: ribosomal RNAs.
RNA polymerase II: protein-coding RNA and snoRNA, miRNA, IncRNA, snRNA genes.
RNA polymerase III: tRNA, rRNA and some snRNA.
What is the role of the different general transcription factors?
Proteins that help to position Pol II correctly on the promoter, and pull aside the two strands of DNA and then move Pol II into the elongation mode.
What is the 5’CAP and Poly-A tails? Why are they important?
Protect from degradation of the mRNA and serve as attachment for ribosomes
Signals to the ribosome where to start translation
How is mRNA splicing done? How are the splicing sites recognized?
Introns are removed from pre-mRNA by the spliceosome. The exons are spliced back together. If the introns are not removed, the RNA would be translated into a nonfunctional protein. Splicing occurs in the nucleus before the RNA travels to cytoplasm.
Why do we have alternative splicing and what is it?
Different combinations of splice sites yielding variably spliced mRNA
How is transcription initiated?
When RNA pol II and transcription factors recognize and bind to the promoter region. The RNA polymerase starts transcribing when its tail is phosphorylated.
Name ways that the cell can upregulate several genes at the same time
The cell can use transcription factors.
What is positive and negative feedback regulation and were is it used?
Positive feedback amplifies regulation, negative feedback reduces it.
What is epigenetic inheritance?
The transmission of epigenetic markers from one organism/generation to the next (i.e., from parent to child) that affects the traits of offspring without altering the primary structure of DNA.
An example is parental imprinting, where certain autosomal genes have seemingly unusual inheritance patterns (the gene is silenced depending on which parent it comes from). The consequence of parental imprinting is that imprinted genes are expressed as if they were hemizygous, even though there are two copies of each of these autosomal genes in each cell.
Why do we see a concentration of CG islands in or near genes?
CpG islands are defined as stretches of DNA 500–1500 bp long with a CG: GC ratio of more than 0.6, and they are normally found at promoters and contain the 5′ end of the transcript.
CGIs are usually associated with lack of DNA methylation and can be considered as the best predictors for defining active or potentially active promoter regions
