8. Transcription and processing in prokaryotes

Question 1

The central dogma

Answer 1

Flow of genetic info from DNA to RNA (transcription) to proteins (translation)

Question 2

RNA self-replication

Answer 2

RNA- dependent RNA polymerase activity in RNA viruses

Question 3

RNA can be retrotranscribed to DNA

Answer 3

Retrotranscriptase activity in retroviruses

Question 4

Protein + infection

Answer 4

= prion

E.g., self-reproducing pathogenic proteins

Question 5

Primary function of DNA

Answer 5

Store genetic info.

Question 6

Primary function of RNA

Answer 6

Transducer DNA messages into protein

Question 7

Primary functions of proteins

Answer 7

Read info. And catalyze reactions as ribosozymes

Question 8

Transcription and translation in prokaryote vs eukaryotes

Answer 8

Prokaryotes can’t regulate RNA and protein synthesis

In eukaryotes nucleus divided transcription and translation=greater control of RNA and protein synthesis

Question 9

RNA molecules involved in transcription

Answer 9

MRNA
SnRNA
TRNA
RRNA
MiRNA

Question 10

RNA polymerase

Answer 10

Highly conserved proteins (so function stays same)

Question 11

Steps for DNA info transmission to protein:

Answer 11

1. Gene expression
2. MRNA processing
3. MRNA transport
4. MRNA translation

Question 12

Spiegelman’s experiments

Answer 12

Rapid switch from transcription of E.coli genes to phage genes;

phage hijacks cells transcription machinery, but cells then actively destroy messenger

Question 13

Pulse-chase labeling experiments

Answer 13

Prove RNA synthesized in nucleus and then transported to cytoplasm

Question 14

RNA ribonucleotides

Answer 14

1. Adenosine
2. Guanosine
3. Cytidine
4. Uridine

Question 15

RNA vs. DNA

Answer 15

1. Single vs. double
More options for shape
2. OH groups in position 2
3. Uracil pairs with A during transcription
pairs with A or G when folding 
4. RNA can catalyze reactions

Question 16

Ribozymes

Answer 16

Catalytic RNA

Question 17

mRNA

Answer 17

Messenger RNA

Intermediates that carry genetic info from DNA to ribosomes

Question 18

snRNA

Answer 18

Small nuclear DNA

Structural components of spliceosomes

Question 19

tRNA

Answer 19

Transfer RNA

Adaptors between amino acids and codons in mRNA’s

Question 20

rRNA

Answer 20

Ribosomal RNA

Structural and catalytic components of ribosomes

Question 21

miRNA

Answer 21

MicroRNA

Short, single-stranded RNA’s that block expression of complementary mRNAs

Question 22

Differences between DNA and RNA

Answer 22

Precursors are ribonucleic triphosphate (not deoxy)

Only 1 strand of DNA as template (thus, only 1 direction 5 prime-3 prime)

RNA chains can be initiated de novo (no primer)

Uracil instead of thymine

Question 23

Antisense strand

Answer 23

DNA template strand (complementary to RNA)

Question 24

Sense strand

Answer 24

DNA nontemplate ‘coding’ strand

Identical to RNA molecule (except U & T)

Question 25

RNA synthesis is catalyze by...

Answer 25

RNA polymerases

Question 26

Phosphodiester bond

Answer 26

Free nucleotide triphosphate bonds to hydroxyl strand

Question 27

Sense (+) RNA

Answer 27

RNA product from template strand is complementary

Question 28

Transcription bubble

Answer 28

Region in molecule where strand opens up to allow polymerase

Question 29

Stages of transcription

Answer 29

1. RNA chain initiation (polymerase) 2. RNA chain elongation 3. RNA chain termination (nascent RNA molecule)

Question 30

Holoenzyme

Answer 30

Initiation of transcription (released after)

Question 31

Sigma factor

Answer 31

Initiation of transcription (released after)

Question 32

Stages of initiation (prokaryote)

Answer 32

A)RNA polymerase binds to promoter (via holoenzyme) Formation of phosphodiester bonds between 1st few ribonucleotides B) initiation signaled by sigma removal

Question 33

+1 site

Answer 33

Where transcription starts (between promoter and ATG)

Question 34

UTR

Answer 34

Untranslated RNA; untranslatable regions of RNA transcript 5’ UTR before AUG & 3’ UTR after stop codon

Question 35

Termination signals

Answer 35

Rho dependent | Rho independent

Question 36

Rho-dependent terminators

Answer 36

Require protein factor Stop codons in mRNA triggers release of attached ribosomes (leaves room for rho to bind) Rho migrates on RNA and reaches polymerase at the transcription bubble

Question 37

Rho-independent terminators

Answer 37

Do not require protein factor G-C rich stemloop structure upstream of poly-U sequence Polymerase pauses, backtracks, proceeds, and encounters stem loop Encourages disassociation of RNA and RNA polymerase—> transcript released