Transcription

By Nur Hanani Khan

TRANSCRIPTION

1.	ALPHA-Amanitin is a poison found in the mushroom Amanita phalloides.
	a.  It is a strong inhibitor of RNA polymerase II (mRNA synthesis)		T
	b.  Moderate inhibitor of RNA polymerase I		F
	c.   No effect on RNA polymerase III		F
2.	In transcription, the RNA polymerase recognizes a sequence of bases in one strand of DNA
	a.     Uses deoxyribonucleotides containing A, G, C, and T	F
	b.   to assemble a complementary sequence in the product mRNA	T
	c.    actual coding strand of DNA can be used, simply	F
	d.   the resulting mRNA would have the sense base sequence	F
	e.   it is the antisense or template strand of DNA that is used in transcription	T
	f.    to generate mRNA with the true code that matches the DNA coding sequence.	T
3.	Initiation transcription
	a.  Promoters are sites where transcription factors come together to position DNA polymerase II in front of the gene sequence.	F
	b.  TATA box binds TBP transcription factor	T
	c.  The CAAT box binds to SP-1 transcription factor.	F
	d.  GC box binds to NF-1/CTF transcription factors	F
	e.  Enhancers can also facilitate transcription by interacting with promoter regions, likely by RNA looping to allow contact with RNA polymerase II	T
4.	Elongation of Transcription
	a.                                           The RNA chain is elongated by addition of 3′ nucleoside triphosphates to the 5′ hydroxyl of the growing RNA chain	F
	b.                                          The transcription bubble is formed when RNA polymerase separates the helix to read the antisense strand	T
	c.                                           RNA polymerase does proof read the RNA sequence	F
	d.                                          A supercoiling strain is created ahead of the helix as RNA polymerase spreads it apart to read the template strand, but the strain is relieved when the RNA helix rewinds at the other end of the bubble	F
	e.                                          Antibiotic actinomycin D binds strongly to the DNA helical structure and inhibits RNA polymerase.	T
5.	Production of Mature mRNA
	a.                                           5’ Caps: 7 methylguanylate linked to 5’ end of mRNA by a 5’ to 5’ phosphodiester bond	F
	b.                                           Methylation of this terminal guanine occurs in the cytosol, and is catalyzed by guanine-7-methyltransferase	T
	c.                                            Polyadenylation at the 5’ end are polymers of 200-300 adenylate residues linked with  phosphodiester bonds.	F
	d.                                           poly-A tail is not transcribed from the DNA, but rather is added after transcription by the nuclear enzyme, polyadenylate polymerase, using ATP as the substrate	T
	e. polyadenylation signal sequence (AAUAAA), found near the 3′-end of the RNA, and the poly-A tail is added to the new 3′-end.	T
	f.  Splice junctions usually begin with a consensus sequence AG (the donor site) and end with a consensus sequence GU (the acceptor site).	F