You are a researcher at a small biotech company and your company has just obtain
ID: 179238 • Letter: Y
Question
You are a researcher at a small biotech company and your company has just obtained the license for use of a human GENOMIC DNA fragment putatively encoding a potentially novel protein, which is thought to regulate p53, the known tumor supressor protein. The scientists who originally cloned this GENE fragment HDM5 "claim" that HDM5 shares 90% DNA sequence homology with one of the HDM2 genes (refer to the review Levine & Oren, 2009). They propose that HDM5 may have HDM2-like properties and may be involved in regulating cell proliferation, and thus a good target to potentially develop as a cancer therapy. Your company has asked you to characterize the gene and gene products, as well as to provide an opinion as to its potential human therapeutic uses.
1. How does a genomic DNA fragment differ from a cDNA fragment? Explain in detail
2. Your gene would need to be transcriptionally active in order for mRNA to be transcribed. A transcriptionally active gene compared with a transcriptionally INactive gene would be expected to (you may choose more than one of the following):
a. contain acteylated histones
b. contain unacetylated histones.
c. be sensitive to DNase I.
d. be resistant to DNase I.
Explain why you selected, or did not select, each option.
Explanation / Answer
Answer 1.
GENOMIC DNA
All genes are present. Genes are strcutred as they present in the genome, adjacent to the flanking regions including introns.
cDNA
Most cDNA are not full length copy of there mRNA. The cDNA refelect that of most of the post transcriptionally modified mRNA, not the gene itself.
cDNA is obtained by the reverse transcription of RNA (mRNA) while genomic DNA is the natural genetic material
Answer 2.
a contain acetylated histonesz
Acetylation of histones has been correlated with transcriptionally active chromatin. The core histones (H2A, H2B, H3 and H4) have two domains: a histone fold domain, which is involved in interactions with other histones and in wrapping DNA around the nucleosome core particle, and an amino-terminal tail domain, which extends outside of the nucleosome. The amino-terminal tail domains are rich in lysine and can be modified by acetylation at specific lysine residues. Acetylation reduces the net positive charge of the histones, and may weaken their binding to DNA as well as altering their interactions with other proteins. Importantly, recent experiments have provided direct evidence that histone acetylation facilitates the binding of transcription factors to nucleosomal DNA, indicating that histone acetylation increases the accessibility of chromatin to DNA-binding proteins. Suggesting that transcriptional activation results directly from histone acetylation
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