A) intersex
B) super female
C) super male
D) gynandromorphy
Correct Answer: A
Solution :
Genie balance theory of sex determination was devised to explain the mechanics of sex determination in male Drosophila melanogaster. XO or XY chromosome segregation was interpreted as a means of tipping the balance between maleness and femaleness, whereas more deep-seated processes were involved in the actual process of sex determination. Bridges experimentally produced various combinations of X-chromosomes and autosomes in Drosophila and deduced from comparisons that one X chromosome (X) and two sets of autosomes produced a normal male. Normal males had a ratio of X chromosome to sets of autosomes of 0.5, note that one set of autosomes consists of three chromosomes, one each of chromosomes II, III and IV. (The X chromosome of Drosophila is chromosome-I). This combination of one X and two As resulted in a normal, diploid male; the combination of two X chromosomes and two sets of autosomes (2X + 2A, ratio of 2 : 2 = 1 ) produced a normal diploid female (Table). Flies produced experimentally with 4X/3A were also metafemales. Those with 4X/4A and also those with 3X/3A, both with an X/A ratio = 1, were females. The combinations 3X/4A = 0.75 and 2X/3A = 0.67 were intermediate in characteristics between males and females and were called intersexes. Combinations of 2X/4A = 0.5 were males and those of 1X/3A = 0.33 were metamales. Table: Ratio of X-chromosomes to autosomes and corresponding sex type in Drosophila melanogaster| X-Chromosomes (X) and Autosomes | Ratio X/A | Sex | |
| 1X | 2A | 0.5 | Male |
| 2X | 2A | 1.0 | Female |
| 3X | 2A | 1.5 | Meta female |
| 4X | 3A | 1.33 | Meta female |
| 4X | 4A | 1.0 | Tetraploid female |
| 3X | 3A | 1.0 | Triploid female |
| 3X | 4A | 0.75 | Intersex |
| 2X | 4A | 0.5 | Tetraploid male |
| 1X | 3A | 0.33 | Metamale |
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