AP Biology Review: DNA, Protein Synthesis, and Biotechnology

With regard to the operon pictured, the image on top shows the operon in its normal state, and the image on the bottom shows the operon in the presence of molecule #5 (looks like a + sign). The identities of some of the molecules shown in the picture are given below.

1. RNA polymerase

3. Promoter

4. Operator

6, 7, and 8. Genes of the operon

***Note: In the picture on top, RNA polymerase is UNABLE to bind correctly to the promoter region and initiate transcription of the genes of the operon***

1. What type of operon is shown in the image, and how do you know?

• An inducible operon; it is usually off but can be turned on.

• An inducible operon; it is usually on but can be turned off.

• A repressible operon; it is usually off but can be turned on.

• A repressible operon; it is usually on but can be turned off.

With regard to the operon pictured, the image on top shows the operon in its normal state, and the image on the bottom shows the operon in the presence of molecule #5 (looks like a + sign). The identities of some of the molecules shown in the picture are given below.

1. RNA polymerase

3. Promoter

4. Operator

6, 7, and 8. Genes of the operon

***Note: In the picture on top, RNA polymerase is UNABLE to bind correctly to the promoter region and initiate transcription of the genes of the operon***

What is the role of molecule #5 in regulating the operon?

• It is an inducer, which is used to inactivate the repressor protein (#2) and prevent it from binding to the operator.

• It is an inducer, which is used to activate the repressor protein (#2) and allow it to bind to the operator.

• It is a repressor, which is used to inactivate the repressor protein (#2) and prevent it from binding to the operator.

• It is a repressor, which is used to activate the repressor protein (#2) and allow it to bind to the operator.

Adding acetyl groups to the histone proteins interacting with the DNA of the insulin gene causes the DNA to coil less tightly. What will be the effect on gene expression?

• This will prevent expression of the insulin gene and result in decreased amounts of insulin protein produced.

• This will prevent expression of the insulin gene and result in increased amounts of insulin protein produced.

• This will facilitate expression of the insulin gene and result in decreased amounts of insulin protein produced.

• This will facilitate expression of the insulin gene and result in increased amounts of insulin protein produced

Tags

NGSS.HS-LS1-1

How can multiple types of antibodies be synthesized from the same “antibody gene”?

• Changing the tightness of coiling of the DNA can result in the creation of different antibody proteins.

• Changing the speed of transport of mRNA out of the nucleus can result in the creation of different antibody proteins.

• Changing which introns are spliced out of the pre-mRNA can result in the creation of different antibody proteins.

• Changing the regulatory proteins that bind to the 5’ end of the mRNA and prevent ribosome attachment can result in the creation of different antibody proteins.

The electrophoretic separation of the pieces of DNA in each of the four samples shown to the right was achieved because of differential migration of the DNA fragments in an electric field. This differential migration was caused by the

• relative amounts of radioactivity in the DNA

• number of cleavage points per fragmen

• size of each fragment

• overall positive charge of each fragment

A scientist is using an ampicillin-sensitive strain of bacteria that cannot use lactose because it has a nonfunctional gene in the lac operon. She has two plasmids. One contains a functional copy of the affected gene of the lac operon, and the other contains the gene for ampicillin resistance. Using restriction enzymes and DNA ligase, she forms a recombinant plasmid containing both genes. She then adds a high concentration of the plasmid to a tube of the bacteria in a medium for bacterial growth that contains glucose as the only energy source. This tube (+) and a control tube (-) with similar bacteria but no plasmid are both incubated under the appropriate conditions for growth and plasmid uptake. The scientist then spreads a sample of each bacterial culture (+ and -) on each of the three types of plates indicated below.

If no new mutations occur, it would be most reasonable to expect bacterial growth on which of the following plates?

• 1 and 2 only

• 3 and 4 only

• 5 and 6 only

• 1,2,3, and 4 only

A scientist is using an ampicillin-sensitive strain of bacteria that cannot use lactose because it has a nonfunctional gene in the lac operon. She has two plasmids. One contains a functional copy of the affected gene of the lac operon, and the other contains the gene for ampicillin resistance. Using restriction enzymes and DNA ligase, she forms a recombinant plasmid containing both genes. She then adds a high concentration of the plasmid to a tube of the bacteria in a medium for bacterial growth that contains glucose as the only energy source. This tube (+) and a control tube (-) with similar bacteria but no plasmid are both incubated under the appropriate conditions for growth and plasmid uptake. The scientist then spreads a sample of each bacterial culture (+ and -) on each of the three types of plates indicated below.

The scientist used restriction enzymes for what purpose in the experiment?

• To make the plasmid small enough to transform cells

• To make cuts in the plasmid DNA

• To make the plasmid enter the cells

• To enable the fragments of DNA to form covalent bonds

• To enable the plasmid to recognize the bacterial cells

Tags

NGSS.HS-ETS1-2

A scientist is using an ampicillin-sensitive strain of bacteria that cannot use lactose because it has a nonfunctional gene in the lac operon. She has two plasmids. One contains a functional copy of the affected gene of the lac operon, and the other contains the gene for ampicillin resistance. Using restriction enzymes and DNA ligase, she forms a recombinant plasmid containing both genes. She then adds a high concentration of the plasmid to a tube of the bacteria in a medium for bacterial growth that contains glucose as the only energy source. This tube (+) and a control tube (-) with similar bacteria but no plasmid are both incubated under the appropriate conditions for growth and plasmid uptake. The scientist then spreads a sample of each bacterial culture (+ and -) on each of the three types of plates indicated below.

If the scientist had forgotten to use DNA ligase during the preparation of the recombinant plasmid, bacterial growth would most likely have occurred on which of the following?

• 1 and 2 only

• 1 and 4 only

• 4 and 5 only

• 1, 2, and 3 only

• 4, 5, and 6 only

Actinomycin D is an antibiotic drug that inhibits protein synthesis by blocking transcription. In some cells, the application of the drug does not affect the synthesis of certain proteins. Which of the following best explains such an occurrence?

• Not all proteins need tRNA molecules for their synthesis

• The proteins that are made are using mRNA synthesized before application of the drug.

• Nuclear proteins do not require the cytoplasmic machinery of ribosomes

• Protein synthesis is blocked in the cytoplasm at the ribosome level.

. . . glycine-serine-glycine . . .

1Which of the following DNA strands will code for the amino acid sequence shown above?

• a. . . . ACTCCTTCT . . .

• b. . . . TCTCCGTCG . . .

• c. . . . CCGTCGACT . . .

• . . . . CCTTCGCCT . . .

Tags

NGSS.HS-LS1-1