Gene Expression and Regulation

Question 1

Inhibitors to know!!!

Answer 1

Question 2

process by which an enzyme system converts the genetic information in dsDNA into an RNA strand with a complementary base sequence

Answer 2

trancription

Question 3

RNA synthesis does not require

Answer 3

a primer

Question 4

mRNA in eukaryotes is synthesized by

Answer 4

RNA polymerase II

two or more upstream activating sequences

Question 5

rho-independent terminators:

Answer 5

have a self-complementary region that forms a hairpin

have a conserved string of three A residues that are transcribed into U residues near the 3′ end of the hairpin

Question 6

an array of proteins that work with Pol II form the active transcription complex

Answer 6

transcription factors

Question 7

those required at every Pol II promoter

Answer 7

general transcription factors

Question 8

Transcription factors are: (specificity)

Answer 8

tissue specific

gene specific

Question 9

Enhancer Sequences

Answer 9

• may be long distances upstream or downstream of the start site
• must be on the same strand as the gene
• can be found within introns
• can affect transcription regardless of its orientation

Question 10

Transcription Factor 3A protein has the motif

Answer 10

Zinc finger protein motif

Question 11

= responsible for the synthesis of a transcript called pre-ribosomal RNA (or pre-rRNA)

Answer 11

RNA polymerase I (Pol I)

pre-rRNA contains the precursor for the 18S, 5.8S, and 28S rRNAs

Question 12

RNA polymerase II needs to have

Answer 12

TATA box binding protein and TFIID to transcribe

In Eukaryotes, the TATA box is necessary but not sufficient for strong promoter activity. Additional elements are located between -40 and -110

Question 13

Termination of transcription in eukaryotes requires a

Answer 13

poly-a-addition signal (AAUAAA)

Question 14

Processes and Possible Regulation

Answer 14

Question 15

nucleotidal transferase

Answer 15

does not require a template

Question 16

Always present in constant amounts regardless of the metabolic state of the organism

Answer 16

Constitutive enzymes

Question 17

Usually found in low amounts and can increase when their substrates are present

Answer 17

induced enzymes

Question 18

Enzymes are not synthesized if not needed

Answer 18

Enzyme repression

Question 19

Describes the complete regulatory unit of a set of cluster genes; it includes adjacent structural genes that code for related enzymes or associated proteins and control element

Answer 19

operon

Question 20

genes for products that are required at all times and are expressed continuously

examples: enzymes of central metabolic pathways

cellular concentrations of the proteins encoded vary

Answer 20

housekeeping genes

Question 21

= expression of a gene at approximately constant levels

Answer 21

constitutive gene expression

Question 22

The RNA polymerase-promoter interaction strongly influences the rate of

Answer 22

transcription initiation

Question 23

The lac Operon is subject to ________ regulation

Answer 23

negative

Question 24

lactose (lac) operon includes the genes for:

Answer 24

• β-galactosidase (Z)
• galactoside permease (Y)
• thiogalactoside transacetylase (A) = modifies toxic galactosides to facilitate their removal

the lac operon is repressed in the absence of lactose

repression is not absolute

Question 25

an inducer of the lac operon

Answer 25

allolactose, an isomer of lactose ## Footnote binding of allolactose to the Lac repressor causes a conformational change and dissociation results in expression of lac operon genes

Question 26

phosphodiesterase cleaves

Answer 26

cAMP in the presense of glucose

Question 28

process in which a particular exon may or may not be incorporated into the mature mRNA transcript

Answer 28

alternative splicing occurs in \> 95% of human genes

Question 30

REQUIREMENTS FOR RNA BIOSYNTHESIS

Answer 30

* A double-stranded (ds) DNA template * DNA-dependent RNA polymerases * 4 nucleoside triphosphates * Mg++ for optimal activity * Transcription occurs in the 5’à3’ direction * Only 1 strand of the DNA molecule serves as the template in a given region NO PRIMER NEEDED UNLIKE DNA SYNTHESIS

Question 32

Prokaryotic Subunits of RNA Polymerase from E. coli

Answer 32

* Subunit # Role * α 2 Binds regulatory sequences * β 1 Forms phosphodiester bonds * β’ 1 Binds DNA template * w (omega)1 conformation maintenance & recruitment of the b’ subunit * σ70 1 Recognizes promoter & initiates synthesis * The core enzyme is composed of all the subunits except the sigma subunit. * The holoenzyme is composed of all the subunits, including the sigma subunit. ​

Question 33

Eukaryotic RNA Polymerases

Answer 33

Question 34

Initiation begins with the recognition of the _______ by the \_\_\_\_\_\_\_component of \_\_\_\_\_\_\_

Answer 34

TATA box; TATA box binding protein (TBP); TFIID

Question 35

Differences between transcription in eukaryotes and prokaryotes

Answer 35

* One type of RNA polymerase in prokaryotes and three in eukaryotes * Prokaryotes make POLYCISTRONIC mRNA and eukaryotes make MONOCISTRONIC mRNA. * Prokaryotic mRNA undergoes very little modifications while eukaryotic mRNA undergoes multiple modifications. * This is because mRNA from prokaryotes can be co-transcriptionally translated while eukaryotic mRNA cannot and need modification to increase molecular stability as well as protect against degradation.

Question 36

The base sequence of an intron begins with _______ and the exon ends with \_\_\_\_\_\_\_.

Answer 36

GU; AG

Question 37

Important internal site located 20 to 50 nucleotides upstream of the 3' splice site in introns

Answer 37

branch site

Question 38

Amino acids are activated and attached to their corresponding tRNA by

Answer 38

aminoacyl-tRNA synthetase

Question 39

Formation of aminoacyl-transfer RNAs ( tRNAs)

Answer 39

1. An amino acid first reacts with adenosine triphosphate (ATP), forming an activated amino acid (aminoacyl-adenosine monophosphate [AMP]) and pyrophosphate, which is cleaved to two inorganic phosphates (Pi). 2. The aminoacyl-AMP then forms an ester with the 20-or30-hydroxyl of a tRNA specific for that amino acid, producing an aminoacyl-tRNA and AMP. 3. Once an amino acid is attached to a tRNA, insertion of the amino acid into a growing polypeptide chain depends on the codon–anticodon interaction

Question 40

Steps of Translation

Answer 40

1. Initiation: Involves the assembly of an active ribosomal complex 2. Elongation & Translocation: New amino acids are brought to the ribosome according to the codon sequence and translocated to a growing polypeptide chain 3. Termination: At certain "stop" codons, translation is ended. 4. Release : The newly formed polypeptide is released Note that translation occurs from the amino terminal to the carboxy terminal and mRNA is read in the 5’ to 3’ direction

Question 41

40s ribosomal subunit associates with eIF3 to physically block 40s & 60s subunit association

Answer 41

anti-association factor