7.2 Gene Expression Flashcards
(21 cards)
Transcription Factor
A protein that binds to DNA
Promoter Sequence
Enable the binding of RNA polymerase
promote transcription
Enhancer Sequence
Regulate DNA activity by changing chromatin structure
When open/decondensed: active gene expression
When closed/condensed: gene inactivity
They can either stimulate or inhibit transcription
Epigenetics
Heritable + reversible modifications to DNA
doesn’t involve nucleotide changes
Methylation
Addition of a methyl group to a CpG site
Prevents transcription + affects histone structure
Acetylation
Addition of an acetyl group
Activates chromatin + allows transcription
Heterochromatin
Condensed chromatin
Genes aren’t available to be copied
Euchromatin
Lightly packed chromatin
Genes are available to be copied
Non coding RNA
RNA molecules aren’t translated into proteins
ncRNA coats 1 X chromosome
supercoils + condenses
leaves the chromosome inactive
RNA splicing
1) Gene is transcribed - results in pre mRNA
2) All introns + some exons removed
3) Remaining genes are joined together by enzyme complexes called spliceosomes
Stem Cells
Undifferenciated cells which have the ability to differenciate into many different cell types
Multipotent stem cells
Gives rise to multiple cell types
Pluripotent stem cells
Gives rise to many specialised cells but not placental cells
Totipotent stem cells
Gives rise to all types of specialised cells
Totipotency differenciation
Zygote contains totipotent cells
capable of forming all cell types
DNA demethylation ensures all genes are accessible for early development
Pluripotentency differenciation
Inner mass cell contains pluripotent stem cells
DNA methylation starts silencing genes related to extra embryonic development
Histone acetylation maintains pluripotency in ESC’s
Somatic Cells
Pluripotency genes are silenced
increase DNA methylation at gene promoters
Histone deacetylation leads to gene repression
NcRNA’s fine tune gene expression
Induced pluripotent stem cells
Adult stem cells that have been reprogrammed to become pluripotent again
1) Fibroplasts are taken from skin samples
2) Viruses are used as vectors to introduce 4 genes for transcription factors
this activates specific genes in adult cells + produces pluripotent cells
3) These behave similarly to ESC’s
IPSC’s vs ESC’s
No embryo destruction
Risk of rejection
No embryo destruction
ESC’s are derived from the inner cell mass
this destroys a potential human life
IPSC’s are derived from somatic cells
no ethical issues
Risk of Rejection
IPSC’s can be from a patient’s own cells
reduces risk of immune rejection
