11/15/17 Flashcards
Synergistic Effects
several copies of the same or different transcription factors bind to adjacent sites that leads to an amplified effect
DNA binding Domains
Helix-turn-helix
Zinc finger
Helix loop helix
Leucine Zipper
Enhanceosomes
A large protein complex that acts synergistically with transcription factors to enhance transcription
Eukaryotic cells must be able to:
- Turn off expression of most of the genes in the genome
- Generate thousands of patterns of gene expression with a limited number of regulatory proteins
- RNA Polymerase II complex must be present (Transcription factors & RNA Polymerase II)
Promoter
contains a TATA Box, where the RNA Polymerase II complex must bind
Promoter Proximal Elements
bind to proteins that assist RNA Polymerase in binding to the Promoter
Distant-independent Elements
Enhancers and Silencers
Enhancers
Increase Transcription rates
Silencers
Reduce Transcription rates
Transcription factors need to:
- Bind to DNA
- Activate or repress transcription
- Two domains (one that binds to DNA and one that influences transcription by binding to another protein)
- DNA binding Domains (motifs)
Transcription have the ________ at the amino acid and the _____ at the carboxyl end
DNA binding domain, activation
Heterochromatin
highly condensed chromatin. Very little transcription occurs in these regions.
Parental Imprinting
Genes that are expressed are only inherited for a specific sex (male or female)
Steps required for imprinting:
1) Soon after fertilization certain cells will be set aside that will become germ cells
2) Imprints are removed or erased before these cells actually become germ cells. These markings are methyl groups bound to cytosines. Without their distinguishing marks genes are said to be epigenetically equivalent.
3) After these germ cells become fully formed gametes, imprinted genes will receive the sex specific mark that will determine if they will be active or silent after fertilization.
4) No changes are observed int he base sequences of the DNA of imprinted genes
5) Methyl groups are added to cytosines to inactivate genes
6) Methyl groups are added to cytosines through the action of methyltransferases
7) The level of methylation generally correlates with transcriptional state of the gene
Prader-Willi Syndrome
caused by parental imprinting caused by two inactivated copies of a gene on chromosome 15. The maternal copy is inactivated due to imprinting, the paternal copy is inactive due to mutation.
