Cho biết 2 gen A và B cùng nằm trên 1 cặp NST và cách nhau 40cM một tế bào sinh trùng

Chia sẻ

Một số câu hỏi khác cùng bài thi.

• Đâu là nhận định sai về hoán vị gen?

• Khi cho lai cà chua thuần chủng thân cao [A], hoa đỏ [B], quả tròn [D] với thân thấp [a], hoa vàng [b], quả bầu dục [d] được F1. Cho lai phân tích F1 thu được Fa với số lượng như sau: 240 cây thân cao, hoa đỏ, quả tròn, 240 cây thân thấp, hoa vàng, quả bầu dục, 60 cây thân cao, hoa đỏ, quả bầu dục, 60 cây thân thấp, hoa vàng, quả tròn, 40 cây thân cao, hoa vàng, quả bầu dục, 40 cây thân thấp, hoa đỏ, quả tròn, 10 cây thân thấp, hoa đỏ, quả bầu dục, 10 cây thân cao, hoa vàng, quà tròn. Quy luật di truyền chi phối 3 tính trạng này là:

• Hoán vị gen có vai trò [1]Hạn chế xuất hiện các biếndị tổ hợp. [2]Tạo điều kiện cho các gen tốt tổ hợp lại với nhau. [3]Sử dụng để lập bản đồ di truyền. [4]Làm thay đổi cấu trúc NST. Số phương án đúng là

• Khi lai thứ lúa thân cao, hạt gạo trong với thứ lúa thân thấp, hạt đục. F1 thu được toàn cây thân cao, hạt gạo đục. Cho các cây F1 tự thụ với nhau ở F2 thu được 15600 cây bao gồm 4 kiểu hình, trong đó có 3744 cây thân cao, hạt trong. Biết rằng mỗi tính trạng do một gen tác động riêng rẽ qui định. Kiểu gen của F1 là:

• Ở một loài thực vật, hai cặp gen Aa và Bb quy định 2 cặp tính trạng, alen trội là trội hoàn toàn. Khi cho các cây P thuần chủng khác nhau giao phấn với nhau thu được F1. Cho F1 x F1 thu được F2 có tỉ lệ kiểu hình lặn về 2 tính trạng chiếm 4%. Quá trình phát sinh giao tử đực và cái diễn ra như nhau. Theo lí thuyết, tỉ lệ kiểu genthuần chủng trong số các kiểu hình trội về 2 tính trạng là:

• Ở một loài thực vật, gen A quy định thân cao hoàn toàn so với alen a quy định thân thấp; gen B quy định quả tròn trội hoàn toàn so với alen b quy định quả dài; các cặp gen này cùng nằm trên 1 cặp nhiễm sắc thể thường. Lai phân tích cây thân cao, quả tròn thu được F1 gồm 35% cây thân cao, quả dài, 35% cây thân thấp, quả tròn, 15% cây thân cao, quả tròn, 15% cây thân thấp, quả dài. Kiểu gen và tần số hoán vị gen của P là

• Hai gen liên kết [A] và [B] cách nhau 18cM. Một người đàn ông với gen AB/ab kết hôn với một người phụ nữ là ab/ab. Xác suất để hai đứa con đầu tiên đều mang kiểu gen ab/ab?

• Cho phép lai P:

  . Cho rằng hoán vị gen chỉ xảy ra ở một giới thì tần số hoán vị gen bằng bao nhiêu để F1 có tỉ lệ kiểu hình là 1 : 2 : 1?

• Một cơ thể có kiểu gen

  có khoảng cách giữa A và B là 18cM, giữa B và D là 20cM. Tỉ lệ giao tử ABd là
• Ở một ruồi giấm cái có kiểu gen

  , khi theo dõi 2000 tế bào sinh trứng trong điều kiện thí nghiệm, người ta phát hiện 360 tế bào có xảy ra hoán vị gen giữa Vvà v. Như vậy khoảng cách giữa 2 trên là:
• Ở một loài thực vật, alen A quy định quả tròn, alen a quy định quả dài, alen B quy định quả ngọt, alen b quy định quả chua, alen D quy định quả màu đỏ, alen d quy định quả màu vàng. Các tính trạng đều trội hoàn toàn. Xét phép lai AaBDbdx AaBDbd, biết hoán vi ̣ gen chỉ xảy ra trong quá trình giảm phân tạo hạt phấn với tần số 40%. Tỷ lệ xuất hiện loại kiểu hình quả tròn, chua, màu đỏ đời con là:

• Cho biết 2 gen A và B cùng nằm trên 1 cặp NST và cách nhau 40 cM. Một tế bào sinh tinh có kiểu gen

  tiến hành giảm phân, theo lí thuyết sẽ tạo ra loại giao tửAB với tỉ lệ:

• Tần số hoán vị gen như sau: AB = 49%, AC = 36%, BC = 13%, bản đồ gen như thế nào?

• Cho biết không có đột biến, hoán vị gen giữa alen B và bở cả bố và mẹ đều có tần số 20%. Tính theo lý thuyết, phép lai AB/ab x Ab/aB cho đời con có kiểu gen Ab/Ab chiếm tỉ lệ:

• Các tế bào phát sinh giao tử tại vùng chín của một cơ thể đực có kiểu gen AaBbCc/dE giảm phân hình thành giao tử. Biết quá trình giảm phân xảy ra bình thường và có 1/3 số tế bào xảy ra hoán vị gen. Theo lý thuyết, số lượng tế bào sinh dục chín tối thiểu tham gia giảm phân để thu được số loại giao tử tối đa mang các gen trên là

• Cho biết quá trình giảm phân không xảy ra đột biến nhưng xảy ra hoán vị gen với tần số 36%. Theo lí thuyết, tỉ lệ các loại giao tử được tạo ra từ cơ thể có kiểu gen

  là:

• Ở một loài thực vật, tính trạng màu sắc hoa do một cặp gen quy định, tính trạng hình dạng quả do một cặp gen khác quy định. Cho cây hoa đỏ, quả tròn thuần chủng giao phấn với cây hoa vàng, quả bầu dục thuần chủng [P], thu được F1gồm 100% cây hoa đỏ, quả tròn. Cho các cây F1tự thụ phấn, thu được F2có 5000 cây gồm 4 loại kiểu hình, trong đó cây hoa đỏ, quả bầu dục chiếm tỉ lệ 9%. Biết rằng trong quá trình phát sinh giao tử đực với giao tử cái đều xảy ra hoán vị gen với tần số như nhau. Theo lí thuyết số cây hoa vàng, quả bầu dục ở F2là bao nhiêu?

• Ở một loài thực vật, hai cặp alen Aa và Bb qui định 2 cặp tính trạng tương phản, giá trị thích nghi của các alen đều như nhau. Khi cho các cây P t/c khác nhau giao phấn thu được F1. Cho F1giao phấn, được F2. Nếu kiểu hình lặn [do kiểu gen aabb] ở F2 chiếm 3,7% thì kết luận nào sau đây là đúng?

• Ở một loài thực vật, A: thân cao, a thân thấp; B: quả đỏ, b: quả vàng. Cho cá thể

  [hoán vị gen với tần số f = 20% ở cả hai giới] tự thụ phấn. Xác định tỉ lệ kiểu hình cây thấp, quả vàng ở thế hệ sau?

• Giả sử một tế bào sinh tinh có kiểu gen Dd giảm phân bình thường và có hoán vị gen giữa alen B và b. Theo lí thuyết, các loại giao tử được tạo ra từ tế bào này là

• Ở ruồi giấm xét hai cặp gen nằm trên cùng một cặp nhiễm sắc thể thường. Cho hai cá thể ruồi giấm giao phối với nhau thu được F1. Trong tổng số cá thể thu được ở F1, số cá thể có kiểu gen đồng hợp tử trội và số cá thể có kiểu gen đồng hợp tử lặn về cả hai cặp gen trên đều chiếm tỷ lệ 4%. Biết rằng không xảy ra đột biến, theo lý thuyết, ở F1 số cả thể có kiểu gen dị hợp tử về hai cặp gen trên chiếm tỷ lệ

• Khi lai thứ lúa thân cao, hạt gạo trong với thứ lúa thân thấp, hạt gạo đục thu được F1 toàn thân cao, hạt đục Cho F1 tự thụ phấn thu được F2 gồm 15600 cây với 4 kiểu hình trong đó có 3744 cây thân cao, hạt trong. Biết rằng mỗi cặp tính trạng chỉ do 1 gen qui địnhvà mọi diễn biến của nhiễm sắc thể trong giảm phân ở tế bào sinh trứng và tế bào sinh hạt phấn là giống nhau. Tần số hoán đổi gen của F1 là
• Cho cây bố và mẹ dị hợp về 2 cặp gen, kiểu hình cây cao hoa đỏ tự thụ phấn, ở F1 xuất hiện 4 kiểu hình trong đó cây cao, hoa đỏ chiếm tỷ lệ 66%. Phép lai nào dưới đây phù hợp với kết quả trên. Biết rằng tương phản với cây cao là cây thấp; tương phản với hoa đỏ là hoa trắng và hoán vị gen xảy ra 2 bên với tần số bằng nhau.Tìm câu sai:
• Ở một loài thực vật, alen A quy định thân cao trội hoàn toàn so với alen a quy định thân thấp, alen B quy định thân quả đỏ trội hoàn toàn so với alen b quy định quả vàng. Cho cây thân cao quả đỏ giao phấn với cây thân cao, quả đỏ [P], thu được F1 có kiểu hình thân cao quả đỏ chiếm tỉ lệ 54%. Trong các dự đoán sau đây, có bao nhiêu dự đoán đúng về sự di truyền của các tính trạng trên? Biết rằng diễn biến nhiễm sắc thể ở 2 giói giống nhau. Không có đột biến mới phát sinh. [1] Hai cặp gen phân li độc lập [2] Cả 2 cơ thể P đều dị hợp 2 cặp gen, kiểu gen có thể giống nhau hoặc khác nhau. [3] Tỉ lệ kiểu hình trội về một trong 2 tính trạng ở F1 chiếm 42%. [4] Tỉ lệ kiểu gen thuần chủng trong số các cây thân cao, quả đỏ chiếm 2/27
• Ởmột loài sinh vật, hai cặp gen A, a và B, b cùng nằm trên một cặp NST cách nhau 20cM. Hai cặp gen D, d và E, e cùng nằm trên một cặp NST khác nhau và cách nhau 10cM. Biết rằng, không phát sinh đột biến và hoán vị gen xảy ra ở cả hai giới với tần số bằng nhau. Theo lý thuyết, trong tổng số cá thể thu được ở đời con, cá thể có kiểu gen dị hợp về 4 cặp gen từ phép lai AB/ab DE/de x Ab/aB De/de chiếm tỉ lệ là:

Một số câu hỏi khác có thể bạn quan tâm.

• Read the passage and blacken the letter A, B, C or D on your answer sheet to indicate the correct answer to the following qusetions:

  How can a plant kill?

  People kill. Animals kill. Animals and people kill for food, or they kill their enemies. People and animals can move around and find something to kill. They can run away from an enemy. They can kill it if it is necessary.

  Many kinds of animals eat plants. The plants cannot run away from their enemies. Some plants make poison. If an animal eats part of the plant, it gets sick or dies. Animals learn to stay away from these plants. There are many kinds of plants that make poison. Most of them grow in the desert or in the tropics.

  Today farmers use many kinds of poison on their farms. Most of these poisons come from petroleum, but petroleum is expensive. Scientists collect poisonous plants and study them. Maybe farmers can use cheap poison from plants instead of expensive poison from petroleum.

  Question: Scientists……………..poisonous plants.

• Read the passage and blacken the letter A, B, C or D on your answer sheet to indicate the correct answer to the following qusetions:

  How can a plant kill?

  People kill. Animals kill. Animals and people kill for food, or they kill their enemies. People and animals can move around and find something to kill. They can run away from an enemy. They can kill it if it is necessary.

  Many kinds of animals eat plants. The plants cannot run away from their enemies. Some plants make poison. If an animal eats part of the plant, it gets sick or dies. Animals learn to stay away from these plants. There are many kinds of plants that make poison. Most of them grow in the desert or in the tropics.

  Today farmers use many kinds of poison on their farms. Most of these poisons come from petroleum, but petroleum is expensive. Scientists collect poisonous plants and study them. Maybe farmers can use cheap poison from plants instead of expensive poison from petroleum.

  Question: Most of these poisons come from………………….

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: Which of the following statements best expresses the main idea of the passage?

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: Which of the following would a traveler be LEAST likely to obtain at Fort Laramie?

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: The word “boosted” in line 15 is closest in meaning to _______.

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: Which of the following is the most likely inference about the decision to promote gardening at forts?

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: According to the passage, which of the following posed the biggest obstacle to the development of military forts?

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: The word “inhibited” in line 24 is closest in meaning to _______.

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: How did the military assist in the investigation of health problems?

• Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:

  In addition to their military role, the forts of the nineteenth century provided numerous other benefits for the American West. The establishment of these posts opened new roads and provided for the protection of daring adventurers and expeditions as well as established settlers. Forts also served as bases where enterprising entrepreneurs could bring commerce to the West, providing supplies and refreshments to soldiers as well as to pioneers. Posts like Fort Laramie provided supplies for wagon trains traveling the natural highways toward new frontiers. Some posts became stations for the pony express; still others, such as Fort Davis, were stagecoach stops for weary travelers. All of these functions, of course, suggest that the contributions of the forts to the civilization and development of the West extended beyond patrol duty. Through the establishment of military posts, yet other contributions were made to the development of western culture. Many posts maintained libraries or reading rooms, and some – for example, Fort Davis – had schools. Post chapels provided a setting for religious services and weddings. Throughout the wilderness, post bands provided entertainment and boosted morale. During the last part of the nineteenth century, to reduce expenses, gardening was encouraged at the forts, thus making experimental agriculture another activity of the military. The military stationed at the various forts also played a role in civilian life by assisting in maintaining order, and civilian officials often called on the army for protection. Certainly, among other significant contributions the army made to the improvement of the conditions of life was the investigation of the relationships among health, climate, and architecture. From the earliest colonial times throughout the nineteenth century, disease ranked as the foremost problem in defense. It slowed construction of forts and inhibited their military functions. Official documents from many regions contained innumerable reports of sickness that virtually incapacitated entire garrisons. In response to the problems, detailed observations of architecture and climate and their relationships to the frequency of the occurrence of various diseases were recorded at various posts across the nation by military surgeons.

  Question: The author organizes the discussion of forts by ________.

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