DNA

5%

A data table for a typical eukaryotic cell with the timing of the cell cycle is shown above. Calculate the percentage of time the cell spends in nuclear division according to the data in the table. 15% 30% 5% 50%

survive when the herbicide is sprayed on the field.

A gene that codes for resistance to an herbicide has been added to the genome of certain plants. These plants will convert the herbicide to fertilizer. survive when the herbicide is sprayed on the field. die when exposed to the herbicide. produce chemicals that kill weeds growing near them.

UCG-GUU-CAC-GUG

A segment of a gene encoding for a protein in the electron transport chain in the thylakoid membrane of plants is shown here in the DNA sequence. AGC-CAA-GTG-CAC Which of the following best illustrates the mRNA that would be produced during the transcription of this gene segment? CAG-GTG-AAC-CGA UCG-GUU-CAC-GUG TCG-GTT-CAC-GTG GUG-CAC-UUC-GCU

B-E-D-A-C

An onion root smash was performed to examine a layer of root tissue only one cell layer thick. A stain was applied to the cells to visualize the chromosomes. What is the most likely order of letters as a cell progresses through the stages of the cell cycle, including mitosis? C-A-D-E-B D-B-C-A-E A-D-C-B-E B-E-D-A-C

The gene coding for the antigen can be inserted into plasmids that can be used to transform the bacteria.

Antigens are foreign proteins that invade the systems of organisms. Vaccines function by stimulating an organism's immune system to develop antibodies against a particular antigen. Developing a vaccine involves producing an antigen that can be introduced into the organism being vaccinated and which will trigger an immune response without causing the disease associated with the antigen. Certain strains of bacteria can be used to produce antigens used in vaccines. Which of the following best explains how bacteria can be genetically engineered to produce a desired antigen? The DNA of the antigen has to be transcribed in order for the mRNA produced to be inserted into the bacteria. The gene coding for the antigen can be inserted into plasmids that can be used to transform the bacteria. The D N A of the antigen has to be transcribed in order for the m R N A produced to be inserted into the bacteria. The mRNA of the antigen has to be translated in order for the protein to be inserted into the bacteria. The bacteria need to be exposed to the antigen so they can produce the antibodies.

Less than 2%

Approximately what fraction of the human genome encodes proteins? 25% 50% Less than 2% 90%

Deletion, because a thymine is missing, which changes the reading frame.

Cystic fibrosis (CF) is a progressive genetic disease that causes persistent lung infections and affects the ability to breathe. CF is inherited in an autosomal recessive manner, caused by the presence of mutations in both copies of the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Partial nucleotide sequences and the corresponding amino acid sequences for an unaffected individual and an affected individual are modeled in Figure 1. Based on the information in Figure 1, which type of mutation explains the nature of the change in DNA that resulted in cystic fibrosis in the affected individual? Substitution, because the amino acid tryptophan is replaced with glycine. Duplication, because the amino acid leucine occurs twice, which changes the reading frame. Insertion, because an extra guanine is present, which changes the reading frame. Deletion, because a thymine is missing, which changes the reading frame.

Rosalind Franklin used X-ray diffraction methods to demonstrate the helical nature of DNA, while Watson and Crick formulated the double stranded structural model of DNA.

Discuss the contributions of Francis Crick, James Watson, and Rosalind Franklin to the discovery of the structure of DNA. Rosalind Franklin, Watson and Crick first employed the technique of X-ray diffraction to understand the storage of DNA. Since it did not work out, Watson and Crick then ran experiments to ascertain the DNA structure. Rosalind Franklin, Watson and Crick used X-ray diffraction methods to demonstrate the helical nature of DNA, while Rosalind Franklin formulated the double stranded structural model of DNA. Rosalind Franklin used X-ray diffraction methods to demonstrate the helical nature of DNA, while Watson and Crick formulated the double stranded structural model of DNA. Watson and Crick used X-ray diffraction methods to demonstrate the helical nature of DNA, while Rosalind Franklin formulated the double stranded structural model of DNA.

There is a similarity in the ratios of bases A:T and C:G within each organism.

Erwin Chargaff was a biochemist who studied the nitrogenous bases of nucleic acids. Below is data produced by Chargaff that reports on the nucleotide base composition of DNA from various organisms. Which of the following is a conclusion that is supported by the Chargaff data shown below? Since the nucleotide base differences between such varied organisms as octopus and yeast are so small, nucleotide bases must not be an important contributor to the structure of DNA. All organisms have roughly equal amounts of each of the four nucleotide bases. There is a similarity in the ratios of bases A:T and C:G within each organism. The percentage of nucleotide base A is always higher than the percentage of nucleotide base G.

The cell will die beacue it is unable to metabolize the substrate without enzyme A, which is structually specific for the substrate shown

Eukaryotes transcribe RNA from DNA that contains introns and exons. Alternative splicing is one post-transcriptional modification that can create distinct mature mRNA molecules that lead to the production of different proteins from the same gene. Figure 1 shows a gene and the RNA produced after transcription and after alternative splicing. A cell needs to metabolize the substrate illustrated in Figure 1 for a vital cellular function. Which of the following best explains the long-term effect on the cell of splicing that yields only enzyme C mRNA? The cell will remain healthy because all three of the above enzymes can metabolize the substrate, as they are from the same gene. The cell will die because it is unable to metabolize the substrate without enzyme A , which is structurally specific for the substrate shown. The cell will remain healthy because the enzyme C mRNA will undergo alternative splicing again until it transformed into enzyme A mRNA . The cell will remain healthy because enzyme-substrate interactions are nonspecific and enzyme C will eventually metabolize the substrate.

Two strains of S. pneumoniae were used for the experiment. Griffith injected a mouse with heat- inactivated S strain (pathogenic) and R strain (non-pathogenic). The mouse died and S strain was recovered from the dead mouse. He concluded that external DNA is taken up by a cell that changed morphology and physiology.

Explain Griffith's transformation experiments. What did he conclude from them? Two strains of S. pneumoniae were used for the experiment. Griffith injected a mouse with heat-inactivated S strain (pathogenic) and R strain (non-pathogenic). The mouse died and R strain was recovered from the dead mouse. He concluded that external DNA is taken up by a cell that changed morphology and physiology. Two strains of S. pneumoniae were used for the experiment. Griffith injected a mouse with heat- inactivated S strain (pathogenic) and R strain (non-pathogenic). The mouse died and S strain was recovered from the dead mouse. He concluded that external DNA is taken up by a cell that changed morphology and physiology. Two strains of S. pneumoniae were used for the experiment. Griffith injected a mouse with heat-inactivated S strain (pathogenic) and R strain (non-pathogenic). The mouse died and S strain was recovered from the dead mouse. He concluded that mutation occurred in the DNA of the cell that changed morphology and physiology. Two strains of Vibrio cholerae were used for the experiment. Griffith injected a mouse with heat-inactivated S strain (pathogenic) and R strain (non-pathogenic). The mouse died and S strain was recovered from the dead mouse. He concluded that external DNA is taken up by a cell that changed morphology and physiology.

UV photons cause dimers to form, leading to misshapen DNA , which results in replication and transcription errors.

Exposure to ultraviolet (UV) radiation is the leading cause of skin cancer in humans. Figure 1 shows a model of how UV exposure damages DNA. Which of the following statements best explains what is shown in Figure 1 ? The hydrogen bonds between base pairs absorb the UV photons, separating the two DNA strands, which results in rapid DNA replication. UV exposure triggers DNA replication, which results in rapid cell proliferation. UV photons cause dimers to form, leading to misshapen DNA , which results in replication and transcription errors. Naturally occurring dimers are removed by the UV photons, causing misshapen DNA , which results in replication errors.

The enzyme reverse transcriptase reverse transcribes the RNA in the genome of HIV to DNA.

How does the enzyme reverse transcriptase violate the central dogma of molecular biology in HIV? The enzyme reverse transcriptase transcribes DNA to RNA, then again to DNA. There is no protein synthesis. The enzyme reverse transcriptase transcribes the DNA straight into the protein molecules. The enzyme reverse transcriptase reverse transcribes the RNA in the genome of HIV to DNA. The enzyme reverse transcriptase translates the RNA of the HIV into protein and then back to DNA.

D

Identify the promotor region A B C D E

31%

If Erwin Chargaff was analyzing a segment of DNA and found the percentage of thymine at approximately 19%, approximately how much cytosine would you expect to be in the sample. 62% 27% 38% 31%

Each newly synthesized strand remains associated with its template strand to form two copies of the original DNA molecule.

Labeled nucleotides were supplied to a cell culture before the cells began DNA replication. A simplified representation of the process for a short segment of DNA is shown in Figure 1. Labeled DNA bases are indicated with an asterisk (*). Which of the following best helps explain how the process represented in Figure 1 produces DNA molecules that are hybrids of the original and the newly synthesized strands? Each template strand is broken down into nucleotides, which are then used to synthesize both strands of a new DNA molecule. Each newly synthesized strand is associated with another newly synthesized strand to form a new DNA molecule. Each template strand is broken into multiple fragments, which are randomly assembled into two different D N A molecules. Each newly synthesized strand remains associated with its template strand to form two copies of the original DNA molecule.

The reverse transcriptase will produce DNA from the viral RNA , which can be incorporated into the host's genome and then transcribed and translated.

Retroviruses such as HIV and hepatitis B virus use RNA as their genetic material rather than DNA. In addition, they contain molecules of reverse transcriptase, an enzyme that uses an RNA template to synthesize complementary DNA. Which of the following best predicts what will happen when a normal cell is exposed to a retrovirus The reverse transcriptase will produce DNA from the viral RNA , which can be incorporated into the host's genome and then transcribed and translated. The reverse transcriptase will cut the host DNA into fragments, destroying the host cell. The reverse transcriptase will insert the viral RNA into the host's genome so it can be transcribed and translated. The reverse transcriptase will force the host ribosomes to translate the viral RNA prior to polypeptide assembly.

D. No peeling of skin will occur in response to UV exposure.

The diagram illustrates the role of p53 in response to UV exposure. What would be the result of a mutation in the p53 gene that inactivates it? B. Apoptosis will occur in response to UV exposure. D. No peeling of skin will occur in response to UV exposure. C. No DNA damage will occur in response to UV exposure. A. Skin will peel in response to UV exposure.

The repressor protein will not bind to the operator, so the genes of the lactose metabolic pathway will always be expressed, whether or not lactose is present.

The lac operon (shown below) is constitutively active when the lactose, a monosaccharide sugar, is present in the cell. When lactose is present genes z, y, and a are expressed, and lactase is produced. Lactase is an enzyme in a metabolic pathway that catabolizes lactose. Which of the following is the most likely result of a genetic mutation in the operator region of this operon, such that the binding of the repressor protein to the DNA is blocked? RNA polymerase will not bind to the promoter, so the genes of the lactose metabolic pathway will always be expressed, whether or not lactose is present. The RNA polymerase will bind to the promoter but will be unable to initiate transcription unless lactose is present. The repressor protein will be irreversibly bound to the operator and the genes of the lactose metabolic pathway will never be expressed, whether or not lactose is present. The repressor protein will not bind to the operator, so the genes of the lactose metabolic pathway will always be expressed, whether or not lactose is present.

The operon is turned off by a bound repressor until lactose is present and the binding of RNA polymerase is enhanced by transcription factors.

The lac operon is considered both under positive and negative control. Which statement supports this? The operon is turned off by a bound repressor until lactose is present and the binding of RNA polymerase is enhanced by transcription factors. The operon is turned off permanently except when the cell is exposed to lactose and glucose. The operon is turned on until excess lactose turns it off, blocking RNA polymerase from transcribing genes. These genes also have enhancer sequences upstream to promote transcription. The operon is controlled positively by regulatory sequences and negatively by mRNA degradation.

Synthesis of sufficient DNA for two daughter cells occurs in stage II .

The relative amounts of DNA present in the nucleus of a cell at four different stages of the life cycle are shown in Figure 1. Based on Figure 1, which of the following statements correctly links a stage of the cell cycle with the event occurring at that stage? Stage I represents the G2 phase of the cell cycle. The replication of genetic material occurs in stage IV . Synthesis of sufficient DNA for two daughter cells occurs in stage II . Stage III includes mitosis.

Okazaki fragments are short stretches of DNA on the lagging strand, which is synthesized in the direction away from the replication fork.

What are Okazaki fragments and how they are formed? Okazaki fragments are long stretches of DNA on the leading strand, which is synthesized in the direction away from the replication fork. Okazaki fragments are short stretches of DNA on the lagging strand, which is synthesized in the direction away from the replication fork. Okazaki fragments are long stretches of DNA on the lagging strand, which is synthesized in the direction of the replication fork. Okazaki fragments are short stretches of DNA on the leading strand, which is synthesized in the direction of the replication fork.

untranslated DNA sequences in a gene

What are introns? the processed mRNA DNA sequences to which polymerases bind translated DNA sequences in a gene untranslated DNA sequences in a gene

Protein was the primary source of heritable information.

What would Chase and Hershey have concluded if the supernatant contained radioactive labeled-phosphorus? DNA was the primary source of heritable information. Phages were the primary source of heritable information. Protein was the primary source of heritable information. RNA was the primary source of heritable information.

TATA box

Which feature of promoters can be found in both prokaryotes and eukaryotes? octamer box GC box TATA box -10 and -35 sequences

A new polypeptide is produced with a different sequence of amino acids.

Which of the following best explains how mutations in DNA can result in the expression of a new phenotype? The gene is read from the 3' to 5' direction after the mutation. The DNA becomes methylated. tRNA can change polarity and bind to different amino acids. A new polypeptide is produced with a different sequence of amino acids.

The virus uses viral copies of reverse transcriptase to manufacture viral DNA.

Which statement accurately describes what happens immediately after an HIV virus enters a host cell? The virus destroys the host cell's transcriptional machinery. The virus uses viral copies of reverse transcriptase to manufacture viral DNA. The virus replicates its genetic material and synthesizes proteins. The virus incorporates the viral DNA into the host cell's chromosome.

A deletion of the first base in the AGC triplet.

Which statement correctly identifies a mutation that will have the greatest impact on the structure and function of the protein for which it encodes. AGC-CAA-GTG-CAC An insertion of a C at the end of the fourth triplet. A substitution of an A for a T in the third triplet. A substitution of the C for a G in the second triplet. A deletion of the first base in the AGC triplet.

Several codons code for the same amino acid

Which statement explains how a point mutation can have no negative effect on the protein formed from a sequence of DNA? Several codons code for the same amino acid The first codon of a gene is always AUG, so a mutation in that sequence is negligible DNA polymerase and DNA ligase carry out excision repair before translation RNA processing will repair point mutations before mRNA leaves the nucleus