Biotechnology (Unit 6 Standard F) AP Bio

Antigens are foreign proteins that invade the systems of organisms. Vaccines function by stimulating an organism’s immune system to develop antibodies against a particular antigen. Developing a vaccine involves producing an antigen that can be introduced into the organism being vaccinated and which will trigger an immune response without causing the disease associated with the antigen. Certain strains of bacteria can be used to produce antigens used in vaccines. Which of the following best explains how bacteria can be genetically engineered to produce a desired antigen?

• The gene coding for the antigen can be inserted into plasmids that can be used to transform the bacteria.

• The bacteria need to be exposed to the antigen so they can produce the antibodies.

• The DNA of the antigen has to be transcribed in order for the mRNA produced to be inserted into the bacteria.

• The mRNA of the antigen has to be translated in order for the protein to be inserted into the bacteria.

Students subjected three samples of five different molecules to gel electrophoresis as shown in Figure 1.  Which of the following statements best explains the pattern seen on the gel with regard to the size and charge of molecules A and B?

• Molecules A and B are positively charged, and molecule A is smaller than molecule B.

• Molecules A and B are positively charged, and molecule A is larger than molecule B.

• Molecules A and B are negatively charged, and molecule A is smaller than molecule B.

• Molecules A and B are negatively charged, and molecule A is larger than molecule B.

Genetic engineering techniques can be used when analyzing and manipulating DNA and RNA. Scientists used gel electrophoresis to study transcription of gene L and discovered that mRNA strands of three different lengths are consistently produced.  Which of the following explanations best accounts for this experimental result?

• Gel electrophoresis can only be used with DNA (not mRNA), so experimental results are not interpretable.

• RNA polymerase consistently makes the same errors during transcription of gene L.

• Gene L is mutated, so RNA polymerase does not always transcribe the correct sequence.

• Pre-mRNA of gene L is subject to alternative splicing, so three mRNA sequences are possible.

Woolly mammoths are an extinct relative of modern-day elephants. Scientists have uncovered a number of woolly mammoth specimens preserved in the Arctic permafrost, and have extracted DNA from the hair shafts of these animals. This DNA has been studied in the laboratory using the same techniques used to study the DNA of modern-day organisms.  For example, a group of scientists used a sample of woolly mammoth DNA to sequence the animal’s nuclear genome. First, the scientists cut the sample DNA into fragments. Then, the scientists amplified the fragments for sequencing. After sequencing, the scientists used computers to reassemble the fragment sequences to determine the order of nucleotides in the mammoth’s genome.  Which of the following techniques could have accomplished the amplification step of the scientists’ process?

• polymerase chain reaction (PCR)

• DNA sequencing

• bacterial transformation

• DNA gel electrophoresis

A scientist constructs a recombinant bacterial plasmid that contains a gene conferring resistance to the antibiotic tetracycline (tet). The scientist transforms cultures of E. coli bacteria with the recombinant plasmid, then incubates the cultures overnight on plates containing media without tetracycline (tet-) and with tetracycline (tet+).  Assuming the transformation protocol was successful, which of the following best predicts the bacterial growth pattern expected after the incubation period?

• (tet-)=some bacterial growth and (tet+)=high bacterial growth

• (tet-)=no bacterial growth and (tet+)=some bacterial growth

• (tet-)=high bacterial growth and (tet+)=no bacterial growth

• (tet-)=high bacterial growth and (tet+)=some bacterial growth

The melanocortin-1-receptor (Mc1r) gene helps determine the coat color phenotype in rock pocket mice.  A researcher collected DNA from individual rock pocket mice and used DNA sequencing to identify the order of nucleotides in the Mc1r gene for each mouse. A subset of the sequencing data, which shows the results for two mice, is shown in Figure 1. Which of the following can be determined from the data in Figure 1?

• Mouse 1 and Mouse 2 differ in at least one nucleotide of the Mc1r gene.

• Mouse 2 has a longer coat than Mouse 1 does.

• Mouse 1 produces a functional Mc1r protein, while Mouse 2 does not.

• Mouse 2 is a transgenic organism, while Mouse 1 is not.