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22 Cards in this Set

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At what levels can regulation of gene expression occur?
1) transcription 2) RNA processing 3) mRNA transport 4) regulation of mRNA stability 5)translation 6) post-translation modification
What does every transcription factor contain?
At least one activation domain and a DNA-binding domain
What do the activation and the DNA-binding domains do?
1) Activation - interacts with RNA polymerase or other transcription factors
2) DNAbinding - allows the protein to bind to the regulatory sequence on the DNA
Most transcription factors bind to the DNA as _____. (structurally speaking)
Dimers
Do the DNA-binding domain and the activation domain function co-dependently or independently?
Independently. eg: if DNA-binding domain of GAL-4 protein is replaced by the DNA-binding domain of lexA, the transcription factor now recognizes the lexA recognition sequence in the DNA.
What do positive feedback loops do?
Create cell memory - the initial expression of such a protein in response to a transient signal causes the cell to continue to express this protein ("remembered" by all descendants of cell)
What are the five beta-like globin genes in humans?
epsilon, gamma G, gamma A, delta, and beta
What globin gene is predominantly fetal and which is predominantly adult?
gamma and beta, respectively
What are the two stages of gene activation?
1) Activation of chromatin
2) Binding of transcription factors
What happens when a steroid hormone binds to the glycocorticoid receptor (GR) - hsp90 complex?
It becomes active - hsp90 dissociates, the activated GR migrates to the nucleus, and it binds to a sequence called "glucocorticoid response element." This binding facilitates intiation of transcription
What are some examples of steroid receptors and what do they have in common?
Glucocorticoid, estrogen, thryoid hormone, progesterone, vitamin D and retinoic acid receptors.
They all share a common DNA-binding domain that forms two zinc fingers.
Like transcription factors, all steroid receptors bind to DNA as _______.
dimers
How is the differentation of embryonic cell into specialized cells regulated?
By turning specific genes on and off at the appropriate times.
What are the imaginal disks in a Drosophila larvae?
These are 20 cells that remain functionally dormant - arrested in further differentiation until pupation, when, under the influence of the hormone ecdyson, each disk develops into a different adult structure.
What three types of genes affect the segmentation pattern of the developing fly?
1) Maternal effect genes
2) Segmentation genes
3) Homeotic genes
What do maternal effect, segmentation and homeotic genes do?
Maternal effect - affect development of embryo along two main axes, anterior-posterior and dorsal-ventral

Segmentation - responsible for proper segmentation of embryo

Homeotic - cause transformations of one type segments into another.
What is the homeobox?
a 60-aa long highly conserved region with a high content of basic amino acids (this suggests that the protein binds to DNA). The homeobox sequence is largely conserved in many other species, including humans.
Homeotic genes cod for transcription factors that are important in early development
The Cytosines are methylated or unmethylated in promoters of active genes?
Kept in unmethylated state.
What type of enzyme puts the methyl group onto the cytosines?
the Methylases
What are CG islands?
Areas about 1000 to 2000 nucleotides long near promoters of genes containing CG sequences, which are relatively uncommon in coding regions of genes.
How can the same gene give rise to two different proteins when expressed in different tissues?
Alternative splicing of pre-mRNA
What does Huntingtin do?
Some how disrupts whole transcription machinery (Werner said this)