T3M3 Flashcards
All embryonic stem cells are…
identical
How many distinct cell types in adult human?
200
Transcription factors are
proteins that bind to specific DNA sequences
Controlling which gene is active along the chromosome leads to
vast array of cell types found throughout our bodies
Both prokaryotes and eukaryotes have
proteins that are involved with activating and repressing transcription and utilize RNA polymerase to bind to promoters that are upstream of genes to initiate transcription
In the prokaryotic genome
groups of related genes with similar functions can often be found clustered together into operons transcribed by a single promoter
eukaryotic genome
each gene is controlled by its own promoters
and enhancers
DNA in eukaryotes is organized into
highly compacted chromatin
DNA in tightly wound chromatin fibers makes for
- fit all the DNA within the nucleus
- DNA to be moved around during cell division
Winding of DNA in nucleosomes can affect
whether DNA is transcribed or not
Genes within this tightly wound heterochromatin are usually
not expressed
To be able to transcribe a specific gene product
Must unwind DNA
DNA compaction regulates
gene expression
In eukaryotes DNA is
around a complex of histone proteins, forming the nucleosome structure
Each nucleosome contains
an octamer of 8 histone proteins around which approximately 150 DNA base pairs wrap around
When DNA is tightly wound into chromatin
the DNA is not accessible due to the tight winding around the histone proteins
For transcription to occur chromatin must be
unravelled
chromatin unravelled through
chromatin remodelling
chromatin remodeling begins when
an activator protein or transcription factor is
able to bind to an accessible enhancer site. This
leads to the further recruitment of other proteins that can lead to further chromatin remodeling
Transcription requires changes to chromatin structure to enable
transcription factors to bind important DNA regions, recruit RNA polymerase, and facilitate the transcriptional process