In a certain taxon of insects some have 17 chromosomes and the others have 18 chromosomes. The 17 and 18 chromosome-bearing organisms are

Options

A. males and females, respectively
B. females and males, respectively
C. all males
D. all females

Answer

To solve the question regarding the chromosome numbers in a certain taxon of insects, we need to analyze the information provided step by step.

### Step 1: Understand the Chromosome Composition
In the given taxon of insects, there are two groups based on chromosome count: some individuals have 17 chromosomes, while others have 18 chromosomes.

### Step 2: Identify the Chromosome Types
The problem mentions that these insects have a specific type of sex determination system, which is the XO/XX system. In this system:
- Males have one X chromosome (XO).
- Females have two X chromosomes (XX).

### Step 3: Calculate the Total Chromosome Count
- For males (XO):
- They have 16 autosomes + 1 X chromosome = 17 chromosomes total.

- For females (XX):
- They have 16 autosomes + 2 X chromosomes = 18 chromosomes total.

### Step 4: Assign Chromosome Counts to Genders
From the calculations:
- The organisms with 17 chromosomes are males.
- The organisms with 18 chromosomes are females.

### Step 5: Choose the Correct Option
Based on the analysis:
- The correct answer is that the 17 chromosome-bearing organisms are males and the 18 chromosome-bearing organisms are females.

### Conclusion
Thus, the answer to the question is that the 17 and 18 chromosome-bearing organisms are males and females respectively.