Genome of Banana - TOEFL iBT® Reading Practice Test with Answer Key

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Reading Instructions

• You have 15 minutes to read the following passage and answer all 10 questions related to it.  
  
• Most questions are worth 1 point, but the last question is worth more. The directions indicate how many points you will receive for that specific question. 
  
• The specific section/paragraphs have been provided again with the question for ease of understanding and quick solution.
  
• Some questions include a word or phrase that is highlighted in the question as well as in the paragraph for quick reference. 

Have you heard? Scientists have successfully sequenced the genome of the banana, marking a significant advancement in their quest to create improved bananas.

Pat Heslop-Harrison, a plant geneticist at the University of Leicester in England and a coauthor of the report published this week in the journal Nature, commented that examining the genome has unveiled curious things.

One illustration is the presence of sections in the banana genome that appear unrelated to protein synthesis yet are common among various plant species, extending well beyond bananas. The question arises: What functions do these sections serve?

Bits of the banana streak virus remain integrated into the banana genome, although they are fragmented and no longer capable of causing disease.

Bananas lack certain DNA repeats that are typically present in plants as a whole. Intriguingly, on three occasions since diverging from its grass relatives, this group of large herbaceous plants has undergone complete chromosome duplication.

Heslop-Harrison pointed out that two doublings occurred during the Cretaceous-Tertiary boundary, which occurred 65 million years ago, coinciding with the extinction of dinosaurs and numerous other species.

Heslop-Harrison mentioned that similar duplications have been observed in other plant groups during the same period but have not occurred since then. The reason for this phenomenon remains unknown to scientists; however, they speculate that the presence of additional gene copies may have provided a degree of resilience to plants amidst a period of swift climate changes following an asteroid impact on Earth.

Having multiple genes of each type provides a buffer against the loss of gene function within a set. This redundancy ensures that if one gene within a set becomes non-functional, the plant retains another gene that remains functional. Furthermore, this redundancy enhances adaptability to changing environments, as one gene can undergo alterations and be co-opted while the other gene continues to fulfill its original function.

“Heslop-Harrison suggested that the success of bananas over millions of years might be attributed to this factor. He pondered whether the ongoing climate changes could lead to new genome duplications that support plant survival, although this remains uncertain, it is an intriguing possibility to explore.”

French scientists sequenced the genome of the Pahang, a wild Malaysian banana belonging to the species Musa acuminata. This banana species plays a crucial role in the intricate evolution of bananas and plantains consumed globally, including the Cavendish banana commonly found in supermarkets.

The Cavendish banana, which is infertile, is categorized as a triploid, possessing three sets of chromosomes rather than the typical two. While one of these sets originated from Pahang, the remaining genomes were inherited from various other subspecies of Musa acuminata.

The progression occurred gradually, unfolding as follows:

• Millennia ago, two distinct wild banana species originating from different regions of the Southeast Asian islands were introduced into the same geographical area by human activity, resulting in the formation of hybrid varieties. These hybrids, akin to mules in robustness but relatively infertile, emerged from this merging.
• The propagation of their shoots allowed these hybrids to persist without sexual reproduction.
• Over time, these hybrids acquired the capability to produce fruit without the need for fertilization.
• Subsequently, another fortuitous event occurred for most banana varieties, including the Cavendish, leading to the hybrids acquiring three sets of chromosomes. Occasionally, the limited number of viable eggs and pollen produced by these hybrids would contain two sets of chromosomes instead of the usual single set.

When a pollen with two chromosomes fused with an egg containing a single chromosome (or the reverse), it led to the creation of a completely infertile plant, albeit one with more robust fruit.

Occurrences of this nature occurred multiple times and occasionally involved various ancestral banana species.

A group of scientists has dedicated extensive research to the domestication and global dissemination of bananas. They have constructed the narrative by integrating diverse sources of data, such as the genetic makeup of wild and cultivated bananas, microscopic remnants of banana leaves unearthed at archaeological sites, and linguistic variations in the term "banana" across different languages.

Directions: Now answer the questions.

Paragraph 2

Pat Heslop-Harrison, a plant geneticist at the University of Leicester in England and a coauthor of the report published this week in the journal Nature, commented that examining the genome has unveiled curious things.

1. In paragraph 2, the word "curious" is closest in meaning to 
   1. inquisitive
   2. peculiar
   3. nosy
   4. intricate

Paragraph 5

Bananas lack certain DNA repeats that are typically present in plants as a whole. Intriguingly, on three occasions since diverging from its grass relatives, this group of large herbaceous plants has undergone complete chromosome duplication.

1. What is implied by paragraph 5 regarding bananas? 
   1. The traditional classification of the banana genus may be challenging.
   2. Bananas are categorized as a type of grass.
   3. Supermarkets might classify bananas as 'herbs' now.
   4. Due to self-duplication of banana chromosomes, they exhibit greater potential for successful cloning.

1. Why does the author opt for the term "intriguingly" to characterize the phenomenon mentioned in paragraph 5?
   1. To suggest that bananas hold a higher level of fascination compared to other fruits.
   2. To prompt skepticism among readers regarding the assertions made by scientists regarding bananas.
   3. To indicate that the duplication of chromosomes is a unique and captivating event within the realm of plants.
   4. To prompt inquiries into the classification of bananas as either grasses or herbs.

Paragraph 6

Heslop-Harrison pointed out that two doublings occurred during the Cretaceous-Tertiary boundary, which occurred 65 million years ago, coinciding with the extinction of dinosaurs and numerous other species. 

1. Why is the significance stated in paragraph 6 noteworthy?
   1. It implies that the banana adapted its genetic makeup to ensure survival 
   2. It indicates that the lineage of bananas extends back to the era of dinosaurs
   3. It hints that bananas posed a threat to dinosaurs and other creatures 
   4. It establishes that bananas are resistant to alterations in the atmosphere

Paragraph 8

Having multiple genes of each type provides a buffer against the loss of gene function within a set. This redundancy ensures that if one gene within a set becomes non-functional, the plant retains another gene that remains functional. Furthermore, this redundancy enhances adaptability to changing environments, as one gene can undergo alterations and be co-opted while the other gene continues to fulfill its original function. 

1. The term "co-opted" in paragraph 8 is most similar in meaning to:
   1. Decided upon together
   2. Argued against
   3. Removed from the study
   4. Adopted 

Paragraph 9

“Heslop-Harrison suggested that the success of bananas over millions of years might be attributed to this factor. He pondered whether the ongoing climate changes could lead to new genome duplications that support plant survival, although this remains uncertain, it is an intriguing possibility to explore.”

1. The quote in paragraph 9 implies that: 
   1. Bananas could serve as an illustration of how species may modify their genetics to adapt to shifts in the earth's climate and atmosphere.
   2. The genetic mutations observed in bananas do not necessarily relate to other species.
   3. The focus should be solely on genetic structure when forecasting survival.
   4. While bananas have endured thus far, there is no assurance of their survival amid forthcoming substantial atmospheric changes. 

1. The article states that all of the following are stages in the banana's evolution EXCEPT:
   1. The emergence of banana hybrids with three sets of chromosomes
   2. The fusion of two distinct banana species
   3. The widespread and effortless reproduction of bananas through fertilization
   4. The acquisition of the capability to produce fruit without fertilization 

Paragraph 12

The progression occurred gradually, unfolding as follows:

• Millennia ago, two distinct wild banana species originating from different regions of the Southeast Asian islands were introduced into the same geographical area by human activity, resulting in the formation of hybrid varieties. These hybrids, akin to mules in robustness but relatively infertile, emerged from this merging.
• The propagation of their shoots allowed these hybrids to persist without sexual reproduction.
• Over time, these hybrids acquired the capability to produce fruit without the need for fertilization.
• Subsequently, another chance event occurred for most banana varieties, including the Cavendish, leading to the hybrids acquiring three sets of chromosomes. Occasionally, the limited number of viable eggs and pollen produced by these hybrids would contain two sets of chromosomes instead of the usual single set. 

1. The term "chance" as used in paragraph 12 is most similar in meaning to:
   1. random
   2. gamble
   3. risky
   4. opportune

1. Which of the following is NOT listed as a type of banana in the article? 
   1. Cavendish
   2. Dolus mundi 
   3. Musa acuminata 
   4. Plantains

1. Instructions: Below is an introductory sentence for summarizing the passage. You need to choose three answer choices that represent the most significant ideas in the passage to complete the summary. Some answer choices are irrelevant or minor ideas not discussed in the passage. This question is worth 2 points.
   
   Scientists have recently achieved a breakthrough by sequencing the banana genome, leading to significant advancements in banana improvement. 
   
   •  
   •  
   •  

   Answer Choices 

   1. The discovery of unusual sections in the banana genome raises questions about their functional roles in various plant species.
   2. The presence of additional gene copies in bananas provides resilience and adaptability to changing environments.
   3. The sequencing of the Pahang banana's genome, a wild Malaysian species, reveals insights into banana evolution and the origin of the Cavendish banana.
   4. The duplication of chromosomes in bananas occurred multiple times during key evolutionary periods, contributing to their genetic diversity.
   5. Scientists speculate that ongoing climate changes could lead to new genome duplications in bananas, potentially enhancing their survival strategies.
   6. Bananas lack certain DNA repeats common in other plants, suggesting unique genetic characteristics.

Answer Key with Explanation for TOEFL Reading Passage - Genome of Banana

1. Answer: B

Explanation: The word "curious" in paragraph 2 is closest in meaning to Option Curious can mean having an unusual or odd quality, which aligns with "peculiar." In this context, the author is discussing unusual sections in the banana genome that are common among various plant species, indicating a peculiarity or distinctiveness that piques interest. The word "inquisitive" (A) is related to curiosity but emphasizes seeking knowledge rather than describing something peculiar. "Nosy" (C) has a negative connotation of being overly interested in others' affairs, which doesn't fit the context. "Intricate" (D) refers to something complex or detailed, which is not the primary meaning of "curious" in this context. 

2. Answer: A

Explanation: Paragraph 5 implies that “The traditional classification of the banana genus may be challenging” (Option A). The paragraph discusses how bananas, specifically the Cavendish banana, possess a triploid genetic makeup with three sets of chromosomes, which is unusual compared to the typical two sets found in most plants. This complexity in genetic structure suggests that the traditional classification of bananas within the genus may pose challenges because of their unique chromosomal arrangement. This statement aligns with the information provided in the paragraph and reflects the implied difficulty in classifying bananas based on their genetic characteristics.

3. Answer: C

Explanation: The author uses the term "intriguingly" in paragraph 5 to indicate that the duplication of chromosomes in bananas is a unique and captivating event within the realm of plants (Option C). The word "intriguingly" suggests that the phenomenon of chromosome duplication in bananas is not only interesting but also noteworthy and uncommon. It implies that this event stands out as fascinating and warrants further investigation or consideration. The author is highlighting the significance of this occurrence in the context of plant biology, emphasizing that it is an intriguing aspect of banana genetics that sets them apart from other plants. Choices A, B, and D are not supported by the context of the passage and do not align with the author's intent in using the term "intriguingly." 

4. Answer: A

Explanation: The significance stated in paragraph 6 is noteworthy because it implies that the banana adapted its genetic makeup to ensure survival (Option A). Paragraph 6 discusses the concept of multiple gene copies providing a buffer against the loss of gene function within a set. This redundancy enhances adaptability to changing environments and ensures the plant retains functional genes even if some become non-functional. This adaptation mechanism suggests that bananas have evolved strategies to cope with environmental changes, which is crucial for their survival as a species. Therefore, option A, which highlights the adaptation of the banana's genetic makeup for survival, best reflects the significance discussed in paragraph 6. Options B, C, and D are not supported by the content of the paragraph. 

5. Answer: D

Explanation: The term "co-opted" in paragraph 8 is most similar in meaning to "adopted" (Option D). "Co-opted" means to take or assume something for one's own use, often by assimilating or incorporating it. In the context of the passage, it refers to the redundancy of genes allowing one gene to undergo alterations and be used while the other gene continues its original function. This usage suggests that the altered gene is adopted or utilized in a new way, similar to how "co-opted" implies adopting or incorporating something into a system or process. The other options are not suitable replacements for "co-opted" in this context. "Decided upon together" (A) implies a joint decision-making process, which is different from adopting or incorporating something. "Argued against" (B) means to present arguments against something, which is opposite in meaning to "co-opted." "Removed from the study" (C) refers to taking something out of a research study or investigation, which is not the meaning conveyed by "co-opted" in the passage. 

6. Answer: A

Explanation: The quote in paragraph 9 implies option A: "Bananas could serve as an illustration of how species may modify their genetics to adapt to shifts in the earth's climate and atmosphere." The paragraph discusses the duplication of chromosomes in bananas and its potential role in enhancing adaptability to changing environments. It mentions that having multiple genes of each type provides a buffer against the loss of gene function within a set, ensuring adaptability. The speculation about ongoing climate changes leading to new genome duplications suggests that bananas may indeed modify their genetics to adapt, which aligns with option Options B and C are not supported by the passage's context, as it discusses the broader implications of genetic modifications in bananas rather than excluding other species or focusing solely on genetic structure. Option D is not directly implied by the paragraph, which focuses more on the potential for genetic adaptations rather than predicting the certainty of bananas' survival. 

7. Answer: C

Explanation: The article states that all of the following are stages in the banana's evolution EXCEPT Option The passage discusses various stages in the evolution of bananas, including the emergence of banana hybrids with three sets of chromosomes, the fusion of two distinct banana species leading to the formation of hybrids, and the acquisition of the capability to produce fruit without fertilization. However, it does not mention the stage of widespread and effortless reproduction of bananas through fertilization. Instead, it emphasizes the gradual development of bananas from hybrids that were initially relatively infertile to acquiring the ability to produce fruit without the need for fertilization, a process outlined in the passage but not specifically referred to as "widespread and effortless reproduction through fertilization." 

8. Answer: A

Explanation: The term "chance" as used in paragraph 12 is most similar in meaning to "random" (Option A). In the context of the passage, "chance" refers to an event that occurs without deliberate planning or predictability. It relates to the fortuitous occurrence of events that led to the hybrids acquiring three sets of chromosomes. This aligns with the idea of something being "random" or occurring by chance, without a specific pattern or intention behind it. The other options, "gamble" (B), "risky" (C), and "opportune" (D), don't capture the sense of randomness implied by "chance" in this context. "Gamble" and "risky" suggest a level of uncertainty or risk-taking, which is not the focus of the passage regarding the natural progression of events. "Opportune" implies something being advantageous or well-timed, which doesn't convey the idea of randomness or unpredictability. 

9. Answer: B

Explanation: The type of banana NOT listed in the article is "Dolus mundi" (Option B). The article mentions the Cavendish banana, Musa acuminata (which is the species to which many banana varieties belong, including the Cavendish), and plantains. However, there is no mention of "Dolus mundi" as a type of banana in the passage. It's possible that "Dolus mundi" may not be a recognized or commonly known variety of banana, or it might be a fictional or less common term not discussed in the context of banana genome sequencing and evolution presented in the article. 

10. Answer: A, B, D

Explanation: The table is completed correctly below.

Option A -  The discovery of unusual sections in the banana genome raises questions about their functional roles in various plant species: This choice reflects the discussion in the passage about sections in the banana genome that are unrelated to protein synthesis but common among various plant species, sparking curiosity about their functions.

Option B - The presence of additional gene copies in bananas provides resilience and adaptability to changing environments: This choice corresponds to the passage's explanation that multiple genes of each type in bananas offer redundancy, ensuring resilience to gene function loss and enhancing adaptability in different environments.

Option D - The duplication of chromosomes in bananas occurred multiple times during key evolutionary periods, contributing to their genetic diversity: This choice captures the passage's mention of complete chromosome duplication events in bananas during evolutionary periods, which has contributed to their genetic diversity.

Incorrect Choices

Option C - The sequencing of the Pahang banana's genome, a wild Malaysian species, reveals insights into banana evolution and the origin of the Cavendish banana: While the sequencing of the Pahang banana's genome is mentioned in the passage, it is not a central idea in summarizing the significant advancements in banana improvement resulting from genome sequencing.

Option E - Scientists speculate that ongoing climate changes could lead to new genome duplications in bananas, potentially enhancing their survival strategies: While climate changes and genome duplications are discussed in the passage, the speculation about ongoing climate changes leading to new genome duplications is not a central idea in summarizing the significant advancements in banana improvement.

Option F - Bananas lack certain DNA repeats common in other plants, suggesting unique genetic characteristics: While the unique genetic characteristics of bananas are briefly mentioned, this detail is not central to summarizing the significant advancements in banana improvement resulting from genome sequencing. 

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