Bio 3 - RNA

Question 1

What is tRNA?

Answer 1

Transfer RNA. Matches up to mRNA and brings the amino acids. They are the smallest type of RNA.

Question 2

What is rRNA?

Answer 2

Ribosomal RNA, involved in protein synthesis. It is part of the ribosome, what binds the amino acids together. The most abundant RNA.

Question 3

What is hnRNA?

Answer 3

Heterogenous nuclear RNA. It is raw, unprocessed newly transcibed RNA. It is not mRNA yet.

Question 4

Where are mRNA and tRNA synthesized?

Answer 4

Nucleoplasm.

Question 5

Where is rRNA synthesized?

Answer 5

In Nucleolus.

Question 6

What are codons?

Answer 6

Sequence of three nucleotides that code for a specific amino acid.

Question 7

What is the start codon?

Answer 7

AUG which codes for Methionine in Eukaryotes.

Question 8

What are the three stop codons?

Answer 8

[Universidad Autonoma de Guadalajara, Universidad Autonoma de Aguascalientes, University of GA]

UAG,UAA,UGA.

Question 9

What is an Operon?

Answer 9

Structural genes that are transcribed + promoter region + all regulatory regions.

Question 10

What is a Transcription Factor?

Answer 10

Must bind to the promoter region (-75 CCAAT box, -25 Hogness/TATA box, and -10 Pribnow/TATAAT box). In order for transcription to take place.

Question 11

What is Operator region?

Answer 11

Binds repressor (stops transcription) or inducers (starts transcription), located between the promoter region and start site.

Question 12

What are the response elements Enhancer region and Repressor region?

Answer 12

Increase or decrease the rate of transcription when bound by protein factors; location may be close to, far from, or within the promoter region.

Question 13

What are common structural motifs in regulation of transcription?

Answer 13

Helix-loop-helix. Helix-turn-helix. Zing Finger. Leucine zipper.

Question 14

What does RNA polymerase I make?

Answer 14

It makes rRNA.

Question 15

What does RNA polymerase II make?

Answer 15

mRNA.

Question 16

What does RNA polymerase III make?

Answer 16

tRNA.

Question 17

What is the mechanism of action of the poison alpha-amanitin?

Answer 17

A mushroom toxin, it inhibits RNA polymerase II. Can cause hepatotoxicity and possibly liver failure.

Question 18

What antibiotic inhibits Prokaryote RNA polymerase?

Answer 18

[The 4 Rs of Rifampin]

Rifampin inhibits RNA polymerase, causes Red secretions, RRRRevs up cytochrome P450.

Question 19

What are the two ways Prokaryotes terminate transcription?

Answer 19

1. Rho factor (an RNA dependent ATPase). Found in E.coli, it uses the energy found in ATP to knock RNA polymerase off of that DNA template. 2. Rho-independent factor; Recognition of termination region in DNA: G-C rich DNA leads to G-C same-strand binding forms stem-loop (hairpin) in RNA leading to pause in RNA polymerase, leading to subsequent weak RNA bonds (uracil rich region), causing separation of RNA polymerase.

Question 20

What process does the hnRNA must undergo to turn into mRNA and leave the nucleus?

Answer 20

Three things: I:Put a cap on the 5’ end (a 7-methyl-guanosine provided by SAM [S-adenosyl-methionine]). II: Polyadenylate the 3’ end (adding 200-250 adenines in a row by Poly-Apolymerase but needs the sequence “AAUAAA”). III:Remove the introns(Splisosomes splice out the introns, the ones that are useless, and leaves the exon, to exit the nucleus and express protein).

Question 21

What amino acid frequently has more coding sequences in the mRNA than are represented in the peptide that is created from that mRNA?

Answer 21

Methionine. It is the AUG, the Start codon, which is usually cleaved off.

Question 22

What is the difference between an intron and an exon?

Answer 22

Introns are NONcoding segments of DNA. Exons are CODING sequences for specific protein products.

Question 23

How is transcription of the lac operon regulated.

Answer 23

By 2 things: I.CAP (catabolite activating protein): Allows RNA polymerase to bind to the DNA and begin transcription of the beta-galactosidase gene, however, it will not bind to the DNA if glucose is present. II.Lac repressor: Prevents RNA polymerase from binding to the DNA, inhibits transcription and beta-galactosidase production. It is constitutively bound to the lac operator region unless lactose is present. Therefore lac operon is only switched on when glucose is absent AND lactose is present.

Question 24

What is mRNA?

Answer 24

Messenger RNA, RNA copied from DNA template. It is the largest type of RNA.