PRACTICE EXAM #3

Question 1

Allolactose induces the synthesis of the enzyme lactase. An E. coli cell is presented for the first time with the sugar lactose (containing allolactose) as a potential food source. Which of the following occurs when the lactose enters the cell?

Answer 1

Allolactose binds to the repressor protein.

Question 2

true or false: A ribosome binds one tRNA at a time.

Answer 2

false

Question 3

true or false: Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome.

Answer 3

true

Question 4

Examples of a pair of codons expected to be read by the same tRNA because the Wobble effect areCAA and _______________

Answer 4

CAU
CAG
CAC

Question 5

Which level control in eukaryotic gene activity involves changes in the polypeptide chain before it becomes functional such as adding phosphate groups?

Answer 5

Posttranslational

Question 6

If mature eukaryotic mRNA is hybridized with its corresponding DNA coding strand (heteroduplex analysis) and visualized by electron microscopy, looping strands of nucleic acid are seen. What do these structure represent?

Answer 6

introns

Question 7

Which level of of control in gene expression regulation is very comon in both prokariotes and eukaryotes?

Answer 7

transcriptional like using activators and repressors

Question 8

true or false: Ribosomes are large RNA structures composed solely of rRNA.

Answer 8

false

Question 9

Which of the classes of RNA molecules is linked with proteins in forming the large and small subunits of a cytoplasmic structure?

Answer 9

ribosomal RNA

Question 10

While prokaryotes are polycystronic, they also have a _______ sequence to bind to the ribosome upstream form the AUG starting code.

Answer 10

Shine-Dalgarno sequence

Question 11

PAP and poly-A binding protiens are related with:

Answer 11

the 3’ terminal of the mRNA

Question 12

With your expert opinion, what do you think it would happen if snRNA are produced but are mutated?

Answer 12

no formation of splisosomes

Question 13

A transcriptional regulator that decreases transcription of a gene from a vast distance is known as a(n)

Answer 13

repressor-silencer.

Question 14

Ribozymes catalyze the reactions ________________, _____________

Answer 14

• splicing

- translation

Question 15

true or false: Ribosomes can start translating an mRNA molecule before transcription is complete.

Answer 15

true

Question 16

If glucose is available in the environment of E. coli, the cell responds with very low concentration of cAMP. When the cAMP increases in concentration, it binds to CAP. Which of the following would you expect would then be a measurable effect?

Answer 16

increased concentrations of sugars such as arabinose in the cell

Question 17

true or false: tRNA bind only one type of amino acid.

Answer 17

false

Question 18

Which is most directly responsible for the sequence of amino acids in a protein?

Answer 18

the sequence of codons in mRNA

Question 19

true or false: A single procaryotic mRNA molecule can be translated into several proteins.

Answer 19

true

Question 20

How does active CAP induce expression of the genes of the lactose operon?

Answer 20

It stimulates the binding of RNA polymerase to the promoter.

Question 21

Which amino acid would you expect a tRNA with the anticodon 5′-CUU-3′ to carry?

Answer 21

lysine

Question 22

In prokaryotes, mRNA molecules commonly contain coding sequences for several different polypeptide chains; such a molecule is called a __________.

Answer 22

Polycistronic mRNA

Question 23

True or false: enhancer-binds to the repressor plus ligand protein

Answer 23

false

Question 24

true or false: genetic code is exactly the same in all organisms.

Answer 24

false

Question 25

THe exons joint together, from a primary transcript, carry the genetic information from the nucleus to the cytosol as it is needed for the construction of a protein as

Answer 25

messenger RNA

Question 26

In polypeptide Met-Phe-Leu, what amino acid has a free carboxyl group?

Answer 26

Leu

Question 27

Altering patterns of gene expression in prokaryotes would most likely serve the organism’s survival in which of the following ways?

Answer 27

allowing the organism to adjust to changes in environmental conditions