25. Eukaryotic Gene Regulation Flashcards
what is chromatin?
DNA + histones = chromatin
the DNA double helix is packaged by proteins called histones, the protein/DNA complex is called chromatin
define differential gene expression
the expression of different genes by cells with the same genome
why is heterochromatin usually not genetically active?
because its highly condensed DNA, meaning RNA polymerase and other proteins needed for transcription initiation dont have access to the DNA template.
why is euchromatin used more in transcription?
because its quite loosely packed DNA so its more accessible for transcription
what is a histone protein?
proteins that package and order nucelosomes (DNA units). it condeneses the lenghth of DNA and helps and gene expression
What are histone acetylations?
the attachement of acetyl groups (-COOH3) to the tails of histone proteins in the nuceleosome. this allows for gene expression
what is DNA methylation?
attachment of methyl groups (-CH3) to bases in the DNA. highly methlylated genes are not usually expressed but REMOVAl of the methyl groups can allow transcription
what are control elements in eukaryotic genes?
segments of noncoding DNA that serve as binding sites for the transcription factors (proteins). this REGULATES TRANSCRIPTION
what are general transcription factors?
a transcription factor to initiate RNA polymerase to transcribe a DNA strand. a general transcription factor is one that can transcribe all protein coding genes
where do transcription factors bind to
directly to the promer DNA
to each other
or RNA polymerase
what is the promoter
a start point where transcription factors bind to it, usually a TATA box
must understand image!
what are control elements? what are the two types and where are they located?
regulatory proteins that bind at specific DNA sequences
proximal control elements (inhibitor) - close to the promoter
distal control elemets (enhancer) - thousands of base pairs away from the promoter
why are the control elements important for the effiecinecy of transctiption initiation?
because when regulatory proteins bind to the control elements, it influences binding of the general transcription factors or the activity of RNA polymerase.
how do different cell types express diffrenent sets of genes?
with cell type-specific transcription. this is due to a combination of a specific type of control elements for differnent genes (eg liver and lens genes)
different cell types have different activators to bind to the transcription factors!
how are genes with related functions coordinatley controlled within each cell?
its acheived with control elements. this happens when each gene has matching control elements that are recognised by a specific activator (regulatory protein).
activators promote transcription of genes no matter where their location is in the genome.
what is alternative RNA splicing?
different mRNA molecules are made from the same primary transcript. depends on which RNA segments are treated as exons and introns
what does alternative RNA splicing result in?
variation of forms of proteins that are made in one type of cell. one pre-mRNA can give rise to different mRNA therefore proteins that have different uses for its function
what evidence suggests that RNA was the first genetic material in the evolution of life on earth?
RNA molecules have catalytic activity. its proven that modern cells use RNA catalysts called ribozymes to splice introns out of RNA molecules.
ribozymes can synthesise complimetry copies of RNA molecules
this is what proteins and DNA does.
what would the effects by of mutations in regulatory DNA sequences?
mutations in the transacting protein factors in specific DNA sequences in the promoter region
causes increase or decrease in transcriptional acitivity.
can cause genetic human disease.
