AP BIOLOGY

Figure 1 represents part of a process that occurs in eukaryotic cells. Which of the following statements best explains why this process occurs? A.) Introns must be removed from the mature transcript because they do not code for amino acids and only sequences coding for amino acids are sent to ribosomes. B.) Introns and exons must be separated onto different mature transcripts because ribosomes can only accept transcripts with either introns or exons, not both. C.) Introns are removed because the inclusion of introns makes the transcript structure too big and this will prevent the transcript from exiting the nucleus. D.) Introns are not retained in the mature transcript because including intron sequences will result in proteins with too many amino acids.

A.) Introns must be removed from the mature transcript because they do not code for amino acids and only sequences coding for amino acids are sent to ribosomes.

The process of translation involves RNA molecules. Figure 1 shows a basic model of the translation process. Which of the following statements best represents the relationship between the RNA molecules involved in translation? A.) tRNA reads mRNA and rRNA adds amino acids to the growing polypeptide. B.) rRNA reads mRNA and tRNA adds amino acids to the growing polypeptide. C.) mRNA reads tRNA and rRNA adds amino acids to the growing polypeptide. D.) tRNA reads rRNA and by mRNA adds amino acids to the growing polypeptide.

A.) tRNA reads mRNA and rRNA adds amino acids to the growing polypeptide.

Which of the following statements best explains the structure and importance of plasmids to prokaryotes? A.) Plasmids are circular, single-stranded RNA molecules that transfer information from the prokaryotic chromosome to the ribosomes during protein synthesis. B.) Plasmids are circular, double-stranded DNA molecules that provide jeans that may aid in survival of the prokaryotic cell. C.) Plasmids are single-stranded, DNA molecules, which are replicated from the prokaryotic chromosome, that prevent viral reproduction within the prokaryotic cell. D.) Plasmids are double-stranded RNA molecules that are transmitted by conjugation that enable other prokaryotic cells to acquire useful genes.

B.) Plasmids are circular, double-stranded DNA molecules that provide jeans that may aid in survival of the prokaryotic cell.

. Erwin Chargaff investigated the nucleotide composition of DNA. He analyzed DNA from various organisms and measured the relative amounts of adenine (A), guanine (G), cytosine ( C), and thymine (T) present in the DNA of each organism. Table 1 contains a selected data set of his results. Which of the following statements best explains the data set? A.) Since the %A and the %G add up to approximately 50 percent in each sample, adenine and guanine molecules must pair up in a double-stranded DNA molecule. B.) Since the %A and the %T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNA molecule. C.) Since the %(A+T) is greater than the %(G+C) in each sample, DNA molecules must have a poly-A tail at one end. D.) Since the %C and the %T add up to approximately 50 percent in each sample, cytosine and thymine molecules must both contain a single ring.

B.) Since the %A and the %T are approximately the same in each sample, adenine and thymine molecules must pair up in a double-stranded DNA molecule.

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. DNA 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.

The genetic material found in two different organisms is analyzed to determine the relative amount of uracil nucleotides contained in an RNA molecule used to copy DNA information. The RNA molecule found in one organism contains 15% uracil and the RNA molecule found in the other organism contains 30% uracil. Which of the following statements best explains why the RNA molecules belong to different organisms other than those represented in Figure 1? A.) The relative amounts of DNA nucleotides should be double the amount of nucleotides in RNA since DNA is double-stranded, and RNA is single-stranded. B.) The relative amounts of adenine in DNA should be the same as the relative amounts of uracil in the RNA used to copy the information. C.) Uracil is a pyrimidine, like cytosine and thymine; therefore, the relative amounts of all three should be the same. D.) DNA molecules should also contain uracil for the RNA molecules to copy the information.

B.) The relative amounts of adenine in DNA should be the same as the relative amounts of uracil in the RNA used to copy the information.

Transcription is a process involved in gene expression and includes the use of enzymes. Figure 1 represents the transcription process. Which of the following statements best explains how RNA polymerase is involved in the transcription process? A.) RNA polymerase synthesizes a new DNA strand in a 5' to 3' direction. B.) RNA polymerase synthesizes mRNA by base-pairing with the coding strand. C.) RNA polymerase copies the gene by base-pairing with the noncoding strand. D.) RNA polymerase copies the gene by synthesizing tRNA from the antisense strand.

C.) RNA polymerase copies the gene by base-pairing with the noncoding strand.

Figure one illustrates a model of the molecules involved in DNA replication and their placement relative to each other. Which of the following statements best explains how topoisomerase and helicase are functionally related during the process of DNA replication? A.)Helicase ads and RNA primer at the 3' end of the template, allowing topoisomerase to synthesize the new strand. B.) Helicase adds nucleotides to the new strand as topoisomerase unwinds the original strands at the replication fork. C.) Helicase synthesizes the new strand as topoisomerase unwinds the original strands. D.) Helicase unwinds the original strands as topoisomerase relieves coiling tension ahead of the replication fork.

D.) Helicase unwinds the original strands as topoisomerase relieves coiling tension ahead of the replication fork.