Topic 7.2 Factors affecting gene expression Flashcards
What is a transcription factor?
A protein that controls the transcription of genes so that only certain parts of the DNA are expressed, e.g. in order to allow the cell to specialise
How do transcription factors work?
They move from the cytoplasm into the nucleus, bind to the DNA near their target gene, and then either increase of decrease the rate of transcription
Transcription factor either bind at the promotor region, which enable the binding of RNA polymerase at the gene or at the enhancer region which make the gene more accessible, often by loosening the binding of the DNA to histone proteins, within the chromatin.
What is splicing?
In eukaryotic cells, mRNA contains non-coding regions called introns. These are removed, and the coding regions are joined back up by enzymes.
This is done by a spliceosome in the nucleus. Spliceosomes are made from protein and RNA
How can splicing result in different products from a single gene?
When exons are joined back together by enzymes, they can be joined in a variety of ways. Therefore several different versions of the RNA can be produced.
What is meant by epigenetics?
A heritable change in gene function without change to the base sequence of DNA
How can non-coding RNA (ncRNA) affect gene expression?
There are many types of non-coding RNA. Some interfere with protein translation, some are invlved in splicing, some chemically modify other RNAs.
How can histone modification affect DNA expression?
Addition of an acetyl group activates chromatin, allowing transcription.
Addition of a methyl group can either activate or inactivate chromatin depending on the postion of lysine.
How can DNA methylation affect gene expression?
Involves addition of a CH3 group to cytosine cases, which prevents transcription factors from binding. Therefore gene transcription is supressed.
How are epigenetics involved in cell differentiation?
Epigenetics control the amount of a cell’s DNA that is transcribed, and therefore ensures only the proteins needed for that specific cell’s function are produced.
