Unit 6 Quizs

Nondisjunction during meiosis can negatively affect gamete formation. A model showing a possible nondisjunction event and its impact on gamete formation is shown in Figure 1. Figure 1. Model of a nondisjunction event Which of the following best describes the most likely impact on an individual produced from fertilization between one of the daughter cells shown and a normal gamete?

Because nondisjunction occurred in anaphase I , all gametes will have an abnormal chromosome number and the individual will likely exhibit phenotypic evidence of the nondisjunction event.

. . . . glycine-serine-glycine . . . Which of the following DNA strands will code for the amino acid sequence shown above?

. . . CCTTCGCCT . . .

Sickle-cell anemia is associated with a mutation in the gene encoding the beta subunit of hemoglobin that results in a change from glutamic acid to valine at position 6. All other amino acids are identical to a normal hemoglobin molecule. Based on the information above, which of the following mutations is the most likely cause of sickle-cell anemia?

A single base-pair substitution in the gene encoding the beta subunit

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. Figure 1. Model of lac operon, comparing repressed and active states Which is a scientific claim that is consistent with the information provided and Figure 1 ? Select all two. The binding of the activators protein to the operator prevents E. coli to metabolize lactose. Allolactose binds to the repressor protein to prevent it from associating with the operator. This allows transcription to occur and lactose to be metabolized Allolactose acts as an inducer that binds to the operator, allowing E. coli to metabolize lactose. When bound to the operator, the repressor protein prevents lactose metabolism in E. coli.

Allolactose binds to the repressor protein to prevent it from associating with the operator. This allows transcription to occur and lactose to be metabolized. When bound to the operator, the repressor protein prevents lactose metabolism in E. coli.

The functions of the loci of the lac operon shown in the diagram are described in the table below. The diagram above represents a segment of the E. coli chromosome that contains the lacI gene and part of the lac operon, a coordinately regulated set of genes that are required for the metabolism of lactose. The presence of lactose, which causes the repressor to be released from the operator, results in increased transcription of the lac operon. Which of the following is the most likely consequence of a mutation at the operator locus that prevents binding of the repressor protein?

Beta-galactosidase will be produced, even in the absence of lactose.

Enzyme used to position nucleotides during DNA replication.

DNA polymerase

The following questions refer to the following DNA strand and table of codons. Question Which of the following modifications of the DNA would produce the greatest change in the primary structure of the polypeptide chain?

Deleting the first T in the second triplet

The table below describes the action of two genes involved in the regulation of nervous system development in the nematode C. elegans. Which of the following claims is best supported by the data?

Gene A promotes neuron development; gene B promotes programmed cell death in neuronal precursors.

What is the molecule illustrated in the figure below?

Nucleic Acid, DNA

Which of the following conclusions is most clearly supported by the representations of nucleic acid #1 and nucleic acid #2 ?

Nucleic acid #1 contains adenine-thymine base pairs, whereas nucleic acid #2 does not.

A student analyzed a viral genome and found that the genome had the following nucleotide composition. • 28% adenine • 20% thymine • 35% cytosine • 17% guanine Which of the following best describes the structure of the viral genome?

Single-stranded DNA

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. 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

The following the DNA sequence is a small part of the coding (nontemplate) strand from the open reading frame of β-hemoglobin gene. Given the codon chart listed below, what would be the effect of a mutation that deletes the G at the beginning of the DNA sequence? 5'- GTT TGT CTG TGG TAC CAC GTG GAC TGA - 3'

The reading frame of the sequence would shift, causing a change in the amino acid sequence after that point.

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 ?

The same transcription factor may regulate the transcription of multiple genes

All of the following are found in RNA except. select two

Thymine Deoxyribose pentose sugar

The following excerpt describes a potential origin of the first living cells on earth. We have proposed that a simple primitive cell, or protocell, would consist of two key components: a protocell membrane that defines a spatially localized compartment, and an informational polymer that allows for the replication and inheritance of functional information. Based on this excerpt, which of the following questions would best direct an investigation on whether the "informational polymer" is DNA or RNA?

Which nitrogenous bases are present in the structure of the informational polymer?

All of the following nitrogenous bases are found in DNA except

uracil

Which of the following molecules associated with a nucleotide? Select three.

11, 13, 12

If a segment of DNA is 5'-TAC GAT TAG-3', the RNA that results from the transcription of this segment will be

3'-AUG CUA AUC-5'

Nuclear pores regulate the passage of substances into and out of the nucleus. Antibodies such as mAb414 have been used to inhibit the movement of substances through the nuclear pores of rat liver cells. Scientists cultured rat liver cells (eukaryotic) and bacteria cells (prokaryotic) in separate dishes with radioactively labeled amino acids. A specific gene in both cell types was engineered to synthesize identical polypeptide chains, and translation of this gene was measured. The procedure was repeated with mAb414 (the inhibitor) added to each of the two cell cultures, and translation was monitored again. Which of the following sets of graphs best summarizes the results of the experiments?

A

The graph below represents the DNA content changes that occur through cell cycle. Which of the following letter represents a cell undergoing DNA Replication?

B

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.

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?

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

Cystic fibrosis is a recessively inherited disorder that results from a mutation in the gene encoding CFTR chloride ion channels located on the surface of many epithelial cells. As shown in the figure, the mutation prevents the normal movement of chloride ions from the cytosol of the cell to the extracellular fluid. As a consequence of the mutation, the mucus layer that is normally present on the surface of the cells becomes exceptionally dehydrated and viscous. An answer to which of the following questions would provide the most information about the association between the CFTR mutation and the viscous mucus?

How does the disrupted chloride movement affect the movement of sodium ions and water by the cell?

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.

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 differential gene expression and influences cellular products (albumin or crystalline) is best supported by evidence in which of the following statements?

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

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' to 3' direction from their DNA templates.

A biology student conducting an experiment on the effect of fertilizer on strawberry growth. The student decided to use Miracle-Gro as the main source of fertilizer. 'Miracle-Gro' is a 15-30-15 fertilizer, meaning that that the powder within contains 15 percent nitrogen, 30 percent phosphorous, and 15 percent potassium. Which of the following statements is/are true? Select two.

Nitrogen will be incorporated into nucleotide Phosphorus will be incorporated into nucleic acids

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.

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. Table 1. Nucleotide composition of sample DNA from selected organisms OrganismRelative Amounts of Bases%A%G%C%T%(G+C)%(A+T)Octopus33.217.617.631.6 35.2 64.8Chicken28.022.021.628.4 43.7 56.4Rat28.621.420.528.4 42.9 56.0Grasshopper29.320.520.729.3 41.2 58.6Wheat27.322.722.827.1 45.5 54.4 Which of the following statements best explains the data set?

Since the %C and the %G are approximately the same in each sample, cytosine and guanine molecules must pair up in a double-stranded DNA molecule.

Which of the following statement is/are true? Select two.

Since the %C and the %G are approximately the same in each sample, cytosine and guanine molecules must pair up in a double-stranded DNA molecule. 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.

Sickle-cell anemia is an inherited blood disorder in which one of the hemoglobin subunits is replaced with a different form of hemoglobin. Partial DNA sequences of the HBB gene for normal hemoglobin and for sickle-cell hemoglobin are shown in Figure 1. Partial sequence for normal hemoglobin: Figure 1. Comparison of partial DNA sequences for normal hemoglobin and hemoglobin with a sickle-cell mutation Which of the following best describes the type of mutation shown in Figure 1 that leads to sickle-cell anemia?

Substitution

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

Figure 1. Nucleic acid segments DNA and RNA are nucleic acids that can store biological information based on the sequence of their nucleotide monomers. Figure 1 shows a short segment of each of the two types of nucleic acids. Which of the following best describes a structural difference between DNA and RNA?

The backbone of DNA contains deoxyribose, whereas the backbone of RNA contains ribose.

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. Nucleic acid fragment Which of the following characteristics of Figure 1 best shows that the fragment is RNA and not DNA? select two

The identity of the pentose sugar The identity of each nitrogenous base

Which of the following characteristics would be BEST to identify if the fragment is RNA and not DNA

The identity of uracil base

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

The three-spined stickleback (Gasterosteus aculeatus) is a small fish found in both marine and freshwater environments. Marine stickleback populations consist mostly of individuals with pronounced pelvic spines, as shown in Figure 1. Individuals in freshwater stickleback populations, on the other hand, typically have reduced pelvic spines, as shown in Figure 2. As represented in Figure 1 and Figure 2, the phenotypic difference between marine and freshwater sticklebacks involves Pitx1, a gene that influences the formation of the jaw, pituitary gland, and pelvic spine. Enhancer sequences upstream of the Pitx1 genetic locus regulate expression of the Pitx1 gene at the appropriate times and in the appropriate tissues during development. Previous studies have found that a mutation in the hindlimb enhancer interferes with the formation of a pronounced pelvic spine. In sticklebacks, which of the following is most likely to occur if the jaw enhancer is disabled instead of the hindlimb enhancer?

The jaw does not develop normally, but a pronounced pelvic spine does develop because the Pitx1 gene is expressed in the developing pelvis but not in the developing jaw.

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 Feature of Protein SynthesisProkaryotesEukaryotes Transcription RNA polymerase mRNA Location Present Synthesized Cytoplasm Present Synthesized Nucleus Translation Large Ribosomal Subunit Small Ribosomal Subunit tRNA Location 50S 30S Present Cytoplasm 60S 40S Present Cytoplasm 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.

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. Figure 1. Operons found in three selected bacteria for arsenic removal 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.

There are multiple operons 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.

Iron is an essential nutrient that is acquired by organisms from the environment. When intracellular levels of iron are relatively high, living cells synthesize an iron-storage protein called ferritin. The induction of ferritin synthesis by iron was investigated in rats. Figure 1 shows the results of an experiment in which cellular levels of ferritin protein were measured in the presence or absence of iron and actinomycin D, a drug that inhibits transcription. Figure 2 shows the results of an experiment in which cellular levels of ferritin protein were measured in the presence or absence of iron and cycloheximide, a drug that inhibits translation. In individuals with iron-rich diets, intracellular levels of iron are higher than in individuals with iron-poor diets. Which of the following best explains how organisms regulate ferritin protein levels in response to available iron?

Translation of ferritin mRNA is stimulated by iron.

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. Figure 2. Phytochrome response to exposure to far‑red light 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.

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 .