【GR1724】 The Solution for GRE Biology Practice Test [141-159]

The Solution for GRE Biology Practice Test [141-159]

 

추천글 : 【GRE】 Solution for GRE Biology Practice Test 

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Questions 141-143 refer to the following diagram of a replication fork.

 

 

141. Location of RNA primer 

⑴ answer: A

⑵ At the head of the Okazaki fragment 🄐, an RNA primer exists.

 

 

142. Location of DNA polymerase

⑴ answer: B

⑵ At 🄑, DNA polymerase continuously elongates the sister strand.

 

 

143. Location of DNA with a free 3' OH

⑴ answer: B

⑵ A DNA strand elongates from 5' to 3'.  

 

 

Questions 144-147.

TATA-binding protein (TBP) is a key transcription factor in eukaryotes. A schematic representation of the 240-amino acid TBP of yeast is shown in Figure 1 below, with the positions of two mutations indicated. The boxed area represents the evolutionarily conserved C-terminal domain of TBP, and the shaded (dark) regions of this domain represent two repeated elements involved in DNA binding. One mutation (P65S) changes proline 65 to serine, and the other (Ⅰ143N) changes isoleucine 143 to asparagine.

 

 

Figure 2 below represents autoradiographs of gels containing RNA transcripts produced in extracts of wild-type or mutant cells. Lanes 1-2 are from wild-type yeast (WT), lanes 3-4 are from the Ⅰ143N mutant, and lanes 5-6 are from the P65S mutant, as indicated. Figure 2A shows transcripts of a gene transcribed by RNA polymerase Ⅰ (PolⅠ). Figure 2B shows transcripts of a gene transcribed by RNA polymerase Ⅱ (Pol Ⅱ). Figure 2C shows transcripts of a gene transcribed by RNA polymerase Ⅲ (Pol Ⅲ). Lanes 1, 3, and 5 show transcripts produced at 24 ℃, and lanes 2, 4, and 6 show transcripts produced at 37 ℃. Shading of the bands represents signals of different intensity.

 

 

144. As a control, wild-type TBP was added to mutant extracts prior to transcription analysis. It was observed that wild-type TBP could restore transcription by all three RNA polymerases in mutant extracts. The controls were performed in order to checks

 

 

⑴ answer: A

⑵ The only difference between controls and the others is the involvement of the perturbation of TBP function.

 

 

145. Which of the following conclusions about mutations in TBP is most consistent with the data?

 

 

⑴ answer: C

 

 

146. The 5S rRNA gene is transcribed by RNA polymerase Ⅲ. If transcription of 5S rRNA is assayed as above, more 5S rRNA transcription would be found

 

 

⑴ answer: E

⑵ RNA pol Ⅰ: Wors at nucleolus. Synthesizes 28S rRNA, 18S rRNA, 5.8S rRNA.

⑶ RNA pol Ⅱ : Works at substrate in nucleus. Synthesize mRNA.

⑷ RNA pol Ⅲ : Works at substrate in nucleus. Synthesizes tRNA, 5S rRNA, ncRNA, snRNA.

 

 

147. Which of the following conclusions about TBP is most consistent with the data?

 

 

⑴ answer: D

 

 

Questions 148-151

Bromodeoxyuridine (BrdU) is used to label cells in the S phase of the cell cycle. Lobsters were exposed to BrdU during six 4-hour period during the 24-hour day. The number of labeled neurons in the brain was counted for each 4-hour labeling period, and the means of these counts were plotted as histograms relative to time of day for animals maintained on the normal light/dark cycle (Figure 1: Normal LD) and on the reversed light/dark cycle (Figure 2: Reversed LD). The shaded bars indicate the sampling period at dawn and dusk, which also are shown in the table below. The horizontal bar at the top of the graph indicates illumination conditions (white = light; black = dark; arrows = subjective dusk). The dawn/dusk data for LD and DD (dark/dark conditions) are summarized in Table 1 below.

 

 

 

148. The graphs of mean counts of BrdU-labeled neurons proliferating at different times of day in the lobster brain demonstrate that

 

 

⑴ answer: D

⑵ See 16:30 in Figure 1 and 4:30 in Figure 2.

 

 

149. The graphs demonstrate that the proliferation of new neurons is entrained by 

 

 

⑴ answer: C

 

 

150. Which of the following is best supported by the data when lobsters are exposed to a normal LD cycle followed by constant darkness for three days (normal DD)?

 

 

⑴ answer: C

⑵ The neuronal proliferation patterns of normal DD is the same with that of normal LD (i.e., higher neuron proliferation at dusk).

 

 

151. These experiments demonstrate that neurogenesis in the lobster brain is controlled by 

 

 

⑴ answer: E

 

 

Questions 152-155

Plant species S is pollinated primarily by hummingbirds, whereas bees are the main pollinators of closely related species T. A study was performed to identify which floral traits influence visitation by the two pollinators. Several hundred F₂ hybrids of species S and T were produced in a greenhouse and then planted into a suitable habitat frequented by both hummingbirds and bees. For each individual F₂ plant, the invesigators measured pollinator visitation rates as a function of carotenoid pigment concentration in the petals (Figure 1) and nectar volume per flower (Figure 2). In addition the investigators identified each plant' genotype at the car genetic locus, which influences pigmentation. The car genetic locus has three alleles, c¹, c² and c³ as shown in Figure 3.

 

 

 

 

152. Which of the following statements agrees with the data shown in Figures 1 and 2?

 

 

⑴ answer: E

 

 

153. Which statement accurately descibes the dominance relationship between one pair of alleles at the car locus with respect to carotenoid concentration?

 

 

⑴ answer: B

⑵ c¹ and c² : incomplete dominance

⑶ c¹ and c³ : complete dominance

⑷ c² and c³ : complete dominance 

 

 

154. If plant fitness increases linearly with pollinator visitation rate and the two animal species are equally effective pollinators, which genotype at the car locus would be expected to be most common in plant species T?

 

 

⑴ answer: C

⑵ See Figure 1.

 

 

155. An isolated population of hybrids between species S and T is discovered in an area where hummingbirds have recently gone extinct but bees remain. Assuming these conditions persist, which of the following evolutionary chenages is most likely to occur during the next few hundred generations?

 

 

⑴ answer: C

⑵ See Figure 1.

 

 

Questions 156-159

A comparative study of insulins from a bird (turkey), two mammals (pig and guinea pig), and a fish (bonito) was undertaken to assess the relative biological activity of the hormone. The hormone's ability to stimulate glucose oxidation (and hence, uptake and metabolism) was assayed in isolated fat cells from rats. Identical populations of fat cells were suspended in media containing radioactive glucose (¹⁴C-glucose) and different concentrations of each insulin. Their production of radioactive carbon dioxide (¹⁴CO₂) was then measured for a fixed period of time and the data were expressed as percentages of the maximum value observed for pig insulin. The percentages are plotted in the figure below as a function of the log of the insulin concentration. The resulting plot for each hormone is called a dosage-response curve.

 

 

 

156. What concentration of pig insulin produced a half-maximal effect on glucose oxidation?

 

 

⑴ answer: B

⑵ Michaelis-Menten equation 

 

 

157. The four insulins differ in their ability to stimulate glucose oxidation. In spite of this difference, the hormone may be equally effective in the species from which they were obtained. Which of the following best tests this hypothesis?

 

 

⑴ answer: B

 

 

158. In this study, the dosage-response curve of turkey insulin lies to the left of those generated by the other vertebrate insulins. An identical result was obtained for turkey insulin in several other comparative assays of biological activity. Which of the following provides the best explanation for the relative position of the dosage-response curve of turkey insulin?

 

 

⑴ answer: B

⑵ B : better sensitivity in ligand-receptor affinity

 

 

159. Above 5 ng · mL^-1, pig insulin exerted no further effect on glucose oxidation. Which of the following best explains this result?

 

 

⑴ answer: C

⑵ Generally, the saturation point of dose-response curve means a maximal binding between ligands and receptors.

 

입력: 2023.05.21 15:36