Unit 6 Gene Expression and Regulation

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

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

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

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

The enzyme-regulated processing of ore-mRNA into nature mRNA

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

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

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

Synthesis of polypeptides will be inhibited

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?

There are multiple openings controlling the production of proteins that process and remove arsenite from cells in both H. arsenicoxydans and O. tritici. In contrast, E. coli has only one operon devoted to arsenic removal

Arsenic is a toxic element found in both aquatic and terrestrial environments. Scientists have found genes that allow bacteria to remove arsenic from their cytoplasm. Arsenic enters cells as arsenate that must be converted to arsenite to leave cells. Figure 1 provides a summary of the arsenic resistance genes found in the operons of three different bacteria. E. coli R773 is found in environments with low arsenic levels. Herminiimonas arsenicoxydans and Ochrobactrum tritici are both found in arsenic-rich environments. Researchers claim that bacteria that live in environments heavily contaminated with arsenic are more efficient at processing arsenic into arsenite and removing this toxin from their cells. Justify this claim based on the evidence shown in figure 1.

Liver cells possess transcriptional activators that are different from those of lens cells

Both liver cells and lens cells have the genes for making the proteins albumin and crystalline. However, only liver cells express the blood protein albumin and only lens cells express crystalline, the main protein in the lens of the eye. Both of these genes have enhancer sequences associated with them. The claim that gene regulation results in different gene expression and influences cellular products (albumin of crystalline) is best supported by evidence in which of the following statements?

Different genes may be regulated by the same transcription factor.

Figure 1 illustrates processes related to control of transcription and translation in a cell. Which of the following scientific claims is not consistent with the information provided in figure 1?

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

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. Which is a scientific claim that is consistent with the information provided and Figure 1?

The antisense strand, because it is serving as a template

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

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

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. The features of this model provide evidence for which explanation of why all growing strands are synthesized in a 5' to 3' direction?

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

Histone methyl transferases 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. What scientific claim is most consistent with these findings?

The two processes will occur simultaneously in prokaryotes but not eukaryotes

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. 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?

When inactive phytochrome Pr is activated by red light to become phytochrome Pfr, it is transported into the nucleus where it binds to the transcription factor PIF3 at the promoter. This stimulates transcription, ultimately leading to protein production. Far-red light inactivates the phytochrome, which will turn transcription off by not binding to PIF3.

Phytochromes are molecules that change light stimuli into chemical signals, and they are thought to target light-activated genes in plants. A study was conducted to determine how certain cell proteins were made in a plant cell using a phytochrome. Figures 1 and 2 represent findings from the study. Use the response models shown in figures 1 and 2 to justify the claim that phytochromes regulate the transcription of genes leading to the production of certain cellular proteins.