Question

What is the difference between gynandromorphs and intersexes in {Drosophila?}

• A. Intersexes are genetically similar throughout their bodies, whereas gynandromorph consists of two genetically different tissues
• B. Intersexes are not genetically similar throughout their bodies, whereas gynandromorph genetically similar throughout their bodies
• C. Intersexes are sterile, whereas gynandromorphs are genetically similar throughout their bodies
• D. Intersexes are genetically similar throughout their bodies, whereas gynandromorph consists of four genetically different tissues

Hint:

Remember the prefixes:

\textbf{Inter-} means "between," so intersexes have a phenotype between male and female, caused by a uniform but abnormal genetic ratio.
\textbf{Gyn-} means female and \textbf{andro-} means male. A gynandromorph is a single organism with both male and female parts, resulting from a genetic mosaic. \end{itemize}

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
This question addresses two specific types of sexual development abnormalities in {Drosophila}, which are caused by different genetic mechanisms.

Step 2: Detailed Explanation:
- Intersexes: In {Drosophila}, sex is determined by the ratio of X chromosomes to sets of autosomes (X/A ratio). An intersex individual has an X/A ratio that is intermediate between that of a normal male (0.5) and a normal female (1.0), for example, a ratio of 0.67 (2X chromosomes and 3 sets of autosomes). Crucially, every cell in the body of an intersex fly has the same abnormal genetic constitution. Thus, they are genetically similar (uniform) throughout their bodies but display an intermediate sexual phenotype.
- Gynandromorphs: A gynandromorph is a genetic mosaic, meaning the organism is composed of cells with different genotypes. In {Drosophila}, this typically occurs when a female (XX) zygote loses one X chromosome from a cell during an early mitotic division. This event creates two distinct cell lines: one that is XX (female) and one that is XO (male). As these cells continue to divide, the organism develops with patches of male tissue and patches of female tissue. Therefore, a gynandromorph consists of two genetically different tissues.

Step 3: Analyzing the Options:
- (A) This statement correctly describes both conditions: intersexes are genetically uniform, while gynandromorphs are mosaics of two genetically different tissues.
- (B) This statement incorrectly reverses the descriptions.
- (C) While intersexes are typically sterile, the second part of the statement incorrectly claims that gynandromorphs are genetically similar.
- (D) This statement correctly describes intersexes but incorrectly states that gynandromorphs consist of four different tissues; it is typically two.

Step 4: Final Answer:
Option (A) provides the most accurate distinction between intersexes and gynandromorphs.