Regulating transcription and translation Flashcards
(8 cards)
What is the importance of transcription factors?
Transcription factors move from the cytoplasm into the nucleus. Here, they bind to specific promoter regions near the start of their target genes.
What is the role of oestrogen in initiating transcription?
Oestrogen is a steroid hormone. Steroids are lipids so can diffuse through the phospholipid bilayer of CSM. In the cytoplasm, oestrogen binds to an oestrogen receptor to form an oestrogen-oestrogen receptor complex. This passes into the nucleus where it acts as a transcription factor which binds to the promoter region of a specific gene.
What is epigenetics?
Epigenetics involves heritable changes in gene function without changes to the base sequence of DNA. These changes are caused by changes in the environment that inhbit transcription by increased methylation of DNA or decreased acetylation of associated histones.
How does increased methylation of DNA inhibit transcription?
A methyl (CH3) group becomes attached to the DNA coding for a gene. This always attaches at a CpG site where a C and G are next to each other in the sequence. This changes the DNA structure, making it harder for transcription factors/RNA polymerase to bind to promoter regions/transcribe DNA.
How does decreased acetylation of associated histones inhibit transcription?
DNA is wound around histones to form chromatin. IF acetyl groups bind to chromatin, attraction between DNA and histones reduces making the chromatin ‘relaxed’ meaning it’s easier for transcriptional machinery to bind to DNA. This increase the rate of transcription. If acetyl groups are removed from histone, then the opposite happens as the chromatin closes.
How can translation of mRNA be inhibited?
In eukaryotes and some prokaryotes, translation of the mRNA produced from target genes can be inhibited by RNAi.
How is translation of mRNA inhibited by RNAi?
1) The double strand is separated into 2 strands.
2) One strand combines with a protein.
3) The RNA-protein complex binds to an mRNA strand that is complementary to the siRNA strand.
4) Protein cuts the mRNA into fragments.
5) A processing body degrades the fragments.
Therefore, mRNA is not translated.
