Understanding Sex Chromosomes in Different Organisms

Sex chromosomes are special chromosomes that determine the sex of an individual. Different organisms have different systems for sex determination involving these chromosomes. This question asks us to match specific organisms with their respective sex chromosome constitutions.

Analyzing the Organisms and Sex Chromosome Systems

Let's look at the sex chromosome systems typically found in the organisms listed:

• Grasshoppers: Grasshoppers use the \(\text{XO}\) sex-determination system.
• Drosophila (Fruit Flies): Drosophila use the \(\text{XY}\) sex-determination system.
• Birds: Birds use the \(\text{ZW}\) sex-determination system (note: this is different from \(\text{XX}/\text{XY}\)).

Now let's match the specific individuals mentioned in List-I with the sex chromosomes provided in List-II, based on common biological understanding and the options given:

• (A) Male grasshopper: In the \(\text{XO}\) system, males have one \(\text{X}\) chromosome and no \(\text{Y}\) chromosome or its equivalent. Their sex chromosomes are represented as \(\text{XO}\). Looking at List-II, (IV) is \(\text{XO}\). So, (A) matches (IV).
• (B) Male Drosophila: In the \(\text{XY}\) system, males have one \(\text{X}\) chromosome and one \(\text{Y}\) chromosome. Their sex chromosomes are \(\text{XY}\). Looking at List-II, (I) is \(\text{XY}\). So, (B) matches (I).
• (C) Female bird: Birds use the \(\text{ZW}\) system, where females are \(\text{ZW}\) and males are \(\text{ZZ}\). However, List-II only provides \(\text{XX}\), \(\text{XY}\), \(\text{XO}\). Based on the provided correct answer option, Female bird (C) is matched with (III) \(\text{XX}\).
• (D) Female grasshopper: In the \(\text{XO}\) system, females have two \(\text{X}\) chromosomes. Their sex chromosomes are \(\text{XX}\). Looking at List-II, (II) is \(\text{XX}\). So, (D) matches (II).

Summarizing the Matches

Based on the analysis, and aligning with the potential matches from the options, the correct pairing is:

Let's check the options provided against these matches:

• Option 1: (A)-(III), (B)-(II), (C)-(I), (D)-(IV) - Incorrect
• Option 2: (A)-(III), (B)-(I), (C)-(IV), (D)-(II) - Incorrect
• Option 3: (A)-(IV), (B)-(I), (C)-(III), (D)-(II) - Correct
• Option 4: (A)-(IV), (B)-(II), (C)-(I), (D)-(III) - Incorrect

The matching that aligns with the provided choices is (A)-(IV), (B)-(I), (C)-(III), (D)-(II).

Sex Determination Systems Explained

• \(\text{XY}\) System: Found in mammals and Drosophila. Females are \(\text{XX}\) (homogametic) and males are \(\text{XY}\) (heterogametic). Sex is typically determined by the presence of the \(\text{Y}\) chromosome (specifically, the SRY gene on the \(\text{Y}\) in mammals).
• \(\text{XO}\) System: Found in grasshoppers and some other insects. Females are \(\text{XX}\) (homogametic) and males are \(\text{XO}\) (heterogametic), meaning they have only one \(\text{X}\) chromosome. The ratio of \(\text{X}\) chromosomes to autosomes determines sex.
• \(\text{ZW}\) System: Found in birds, some fish, and some insects. The female is the heterogametic sex (\(\text{ZW}\)), and the male is the homogametic sex (\(\text{ZZ}\)). Sex is determined by the egg (which can carry a \(\text{Z}\) or a \(\text{W}\) chromosome), while the sperm always carries a \(\text{Z}\).

It is important to note that while the \(\text{ZW}\) system is standard for birds, the provided options use \(\text{XX}\)/\(\text{XY}\)/\(\text{XO}\) notation, and the match given for Female bird in the correct option is \(\text{XX}\). Always follow the specific information provided in the question and options during an exam.

Revision Table: Organism Sex Chromosomes

This table summarizes common sex chromosome systems, including the ZW system found in birds which was relevant to the question but not directly listed in the options' chromosome types.

Additional Information on Sex Determination

Sex determination is a fundamental biological process. While chromosomal systems like \(\text{XY}\), \(\text{XO}\), and \(\text{ZW}\) are common, other mechanisms exist, such as environmental sex determination (temperature-dependent in many reptiles) or haplo-diploidy (in bees and ants, where fertilized eggs become females and unfertilized eggs become males).

In the \(\text{XY}\) and \(\text{ZW}\) systems, the heterogametic sex produces two types of gametes regarding sex chromosomes (\(\text{X}\) and \(\text{Y}\), or \(\text{Z}\) and \(\text{W}\)), while the homogametic sex produces only one type (\(\text{X}\) or \(\text{Z}\)). The interaction or presence of these chromosomes dictates development into male or female.