AP bio unit 6 exam

Figure 1 represents a metabolic process involving the regulation of lactose metabolism by E. coli bacteria. Lactose is utilized for energy by E. coli when glucose is not present. Allolactose is an isomer of lactose that is in the environment of these bacteria when lactose is present. The CAP site prevents the binding of RNA polymerase when glucose is present in the environment. The lacZ, lacY, and lacA genes code for proteins needed for lactose metabolism.

B When bound to the operator, the repressor protein prevents lactose metabolism in E. coli.

A model that represents a process occurring in a cell of a particular organism is shown in Figure 1. Figure 1. Process occurring in a cell Which of the following correctly explains the process shown in Figure 1 ?

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

Which of the following statements best explains the structure and importance of plasmids to prokaryotes?

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

Figure 1 illustrates a model of the molecules involved in DNA replication and their placement relative to each other. Figure 1. Model including molecules involved in DNA replication Which of the following correctly explains where DNA replication will begin on the strand oriented 5'→3', reading from left to right?

DNA replication will be initiated immediately to the left of the RNA, since DNA polymerase requires an RNA primer.

Figure 1 illustrates processes related to control of transcription and translation in a cell. Figure 1. Model of a relationship between a transcription factor and selected genes Which of the following scientific claims is most consistent with the information provided in Figure 1 ?

Different genes may be regulated by the same transcription factor.

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?

Synthesis of polypeptides will be inhibited.

Figure 1 represents part of a process essential to gene expression. Figure 1. Model of process involved in gene expression. Which of the following best explains what strand X represents?

The antisense strand, because it is serving as a template

Histone methyltransferases are a class of enzymes that methylate certain amino acid sequences in histone proteins. A research team found that transcription of gene R decreases when histone methyltransferase activity is inhibited. Which scientific claim is most consistent with these findings?

D Histone methylation opens up chromatin at gene RR so transcription factors can bind to DNA more easily.

A model of a process involving nucleic acids is shown in Figure 1. Figure 1. Model of a process involving nucleic acids Which of the following best explains what process is represented in Figure 1 ?

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

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?

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 DNA molecule.

Figure 1 represents part of a process that occurs in eukaryotic cells. There are untranslated regions (UTR) in this sequence. Figure 1. Cellular process involving nucleic acids Which of the following best explains the process represented by Figure 1 ?

The enzyme-regulated processing of pre‑mRNA into mature mRNA

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?

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

Figure 1 shows some relevant details of a model of how a deoxynucleotide, in this case dTMP, is added to a growing strand of DNA. Figure 1. Model showing details of adding a deoxythymidine monophosphate (dTMP) nucleotide to a growing strand of DNA The features of this model provide evidence for which explanation of why all growing strands are synthesized in a 5′ to 3′direction?

The phosphate group, attached to the 5′5′ carbon of the dTMP, forms a covalent bond with the oxygen atom attached to the 3′3′ carbon of the growing strand.

Molecular biologists are studying the processes of transcription and translation and have found that they are very similar in prokaryotes and eukaryotes, as summarized in Table 1. Table 1. Comparison of Selected Features of Transcription and Translation Based on the information in Table 1, which of the following best predicts a key difference in prokaryotes and eukaryotes with regard to transcription and translation?

The two processes will occur simultaneously in prokaryotes but not eukaryotes.