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Block 1 wk1 regulation of gene transciption
Terms in this set (12)
What about bacterial genes/ bacterial transcription allows them to acquire drug resistance, be able to use new food substrates, or produce toxins?
Bacterial transcription is driven by the environment.
Bacterial genes are turned on and off through transcription repressors and activators that react to nutrients, metabolites, and environemntal conditions.
A gene is turned on when RNA polymerase is brought in to the gene's promoter- this allows bacterial to turn genes on or off within second of a stimulus
Basically bacteria can react quickly to environmental factors and regulate transcription accordingly.
The lactose Operon is an example of how bacteria can adapt to their environment by utilizing different food sources. How does the lac operon basically work?
E.coli prefer to metabolize glucose. So when glucose is present repressor protein bind to lac operator- the lac genes are not expressed.
When glucose is not present, but lactose is- the repressor is not bound and transcription of lac genes occurs.
With very few exceptions, every normal cell in the human body has the same DNA sequence- however each cell type is different in how genes are expressed.
What establishes different gene expression programs on the the Same genome?
Regulation of gene transcription- key mechanism in transcription regulation are:
Competition for TF binding sites
Covalent modifications of TFs
Covalent modifications of Nucleosome **
Competition for TF binding sites occurs because
The same gene can be controlled by many combinations of transcription factors depending on cell type
What are the regions of DNA that can regulate distant genes located thousands to millions of nucleotides away?
Discuss how these regions do what they do
They cause the DNA to loop so that the TF on enhancer's transcription elements interact with the transcription factors on the promoter's transcription elements.
What is they study of heritable changes in gene activity that do not involve changes in DNA sequence
There are two types of epigenetic inheritance
Cell to cell- preserves cell identity
Transgenerational-example agouti mouse- skinny gray mouse versus chubby white one- changes in methylation of agouti gene. This means you can transmit your bad behavior to your offspring.
What are the 3 epigenetic mechanisms?
Discuss the 3 mechanisms by which chromatin can regulate genes
1. Euchromatin vs heterochromatin- large portions of genome are organized into open-euchromatin or closed-heterochromatin
2. At the gene level- changes in Nucleosome positioning- open or close certain DNA regions, enabling or disabling the binding of transcription factors.
3. Nucleosomes with messages: covalent modifications of Nucleosomal proteins (histones) signal RNAP II and TF
Which region of genes are often free of nucleosomes?
Promoters and enhancers
What are the most famous noncoding RNAs?
What do they do?
How can they be used to treat disease?
MicroRNAs are small 18-24 nt RNA molecules that can bind to other RNAs (like mRNA) through base complementarity and prevent their function.
MiRNAs repress their targets
MiRNA therapy- they can target individual genes and thus cure diseases including cancers.
DNA methylation is en epigenetic mechanism. Methylation does what to genes? What sequences can be methylated?
CG sequences can be methylated or not
CG sequences are frequent at gene promoters
When CG islands are methylated, genes are usually repressed.
DNA methylation can be transmitted to the next generation- remember the agouti mouse-
Discuss the differences between eukaryotic and prokaryotic genes-
Have small promoters- 100-200 adjacent to gene
Genes can be transferred through various mechanisms to other bacteria on plasmids, transduction, or DNA uptake
Most sequences in the genome code for proteins
Eukaryotes- genes have large promoters- >>1000 nucleotides
Many genes depend on other DNA elements- such as enhancers located millions of nucleotides away
Most sequences don't code for proteins and many of the sequences have unknown functions
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