AP Bio Unit 6

Which of the following statements best explains the data set? A. Since the %A%A and the %G%G add up to approximately 50 percent in each sample, adenine and guanine molecules must pair up in a double-stranded DNADNA molecule. B. Since the %A%A and the %T%T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNADNA molecule. C. Since the %(A+T)%(A+T) is greater than the %(G+C)%(G+C) in each sample, DNADNA molecules must have a poly-AA tail at one end. D. Since the %C%C and the %T%T add up to approximately 50 percent in each sample, cytosine and thymine molecules must both contain a single ring.

B

Which of the following correctly explains the process shown in Figure 1 ? A. DNA replication is occurring because replication is semi-conservative and the new strand is a copy of the template strand. B. Initiation of transcription is occurring because a strand of RNA is being produced from a DNA template strand. C. Translation is occurring because the two strands have separated and a new strand is being produced. D. Alternative splicing of mRNA is occurring because the mRNA strand is being synthesized from only one strand of DNA.

B. Initiation of transcription is occurring because a strand of RNA is being produced from a DNA template strand.

Which of the following best explains what process is represented in Figure 1 ? A. New DNA strands are being synthesized in the 3'3′ to 5'5′ direction from their DNA templates. B. New DNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNA templates. C. A new RNA strand is being synthesized in the 3'3′ to 5'5′ end from its DNA template. D. Two new RNA strands are being synthesized in both directions from their DNA templates.

B. New DNA strands are being synthesized in the 5'5′ to 3'3′ direction from their DNA templates.

Antibiotics can be used to kill the specific pathogenic bacterium, Mycobacterium tuberculosis, that causes tuberculosis. The appearance of antibiotic-resistant strains has made it more difficult to cure M. tuberculosis infections. These antibiotic-resistant bacteria survive and pass on the genes to their offspring, making the resistant phenotype more common in the population. DNADNA analysis indicates that the genes for antibiotic resistance are not normally present in bacterial chromosomal DNA. Which of the following statements best explains how the genes for antibiotic resistance can be transmitted between bacteria without the exchange of bacterial chromosomal DNA? A. The antibiotic-resistant bacteria release a hormone that signals neighboring bacteria to become resistant. B. The genes for antibiotic resistance are located on a plasmid that can be passed to neighboring bacteria. C. The antibiotic-resistant bacteria are the result of bacteria that specifically modify their own chromosomal DNA to neutralize the antibiotics. D. The antibiotic alters the bacterial genome of each bacterium, which results in an antibiotic-resistant population.

B. The genes for antibiotic resistance are located on a plasmid that can be passed to neighboring bacteria.

A processed eukaryotic mRNA...(c) Fill in the boxes in the template to identify the nucleotide sequence, from 3′ to 5′, of the tRNA anticodon that will recognize codon 5 and the tRNA anticodon that will recognize codon 510 of the mRNA template and to identify the amino acids that will be added at these two positions. A codon table is provided for reference.

Codon 5, the anticodon sequence is GCC and the amino acid added is arginine (Arg ). The response also indicates that for codon 510, there will be no tRNA with a complementary anticodon because UAG in the mRNA is a translation stop sequence, and no amino acid will be added/translation terminates.

Antibiotics interfere with prokaryotic cell functions. Streptomycin is an antibiotic that affects the small ribosomal subunit in prokaryotes. Specifically, streptomycin interferes with the proper binding of tRNA to mRNA in prokaryotic ribosomes. Which of the following best predicts the most direct effect of exposing prokaryotic cells to streptomycin? A. Amino acid synthesis will be inhibited. B. No mRNA will be transcribed from DNA. C. Posttranslational modifications will be prevented. D. Synthesis of polypeptides will be inhibited.

D. Synthesis of polypeptides will be inhibited.

A processed eukaryotic mRNA...(d) Referring to the figures provided, explain why the polypeptide produced when the transformed bacteria translate the introduced eukaryotic mRNA provides evidence for the common ancestry of all living organisms.

Polypeptides produced by translation of a processed eukaryotic mRNA by a eukaryotic cell or a prokaryotic cell into which it has been introduced should have the same amino acid sequence because the genetic code is almost universal and the same codon chart can be used for both prokaryotic and eukaryotic organisms.

A processed eukaryotic mRNA...(b) Referring to Figure 1, explain the process illustrated between Step 1 and Step 2.

Steps 1-2 are the growing polypeptide chain attached to the tRNA aligned with codon 3 of the mRNA is transferred to the amino ( NH2) terminus of amino acid 4 ( AA4) attached to the aligned with codon 4 of the mRNA.

A processed eukaryotic mRNA...(a) Describe why translation of an mRNA can start before transcription of the mRNA is complete in prokaryotes but not in eukaryotes.

This is because prokaryotes do not have a nuclear envelope that separates the genome from ribosomes in the cytoplasm of the cell, whereas eukaryotes do.