“No wonder I got such a crash bio briefing! Let’s see. Chromosomes are collections of genes which in turn control characteristics. When an animal is ready to reproduce, its germ-cells—or reproductive cells—each divide into two daughter cells called gametes, each daughter cell possessing one-half the chromosomes of the parent cell, every chromosome in each gamete corresponding to an opposite number chromosome in the other. Process is called meiosis. Correct me if I’m wrong anywhere.”
“And how can a human be wrong?” I asked devoutly.
His face wrinkled. “In the case of humans, the female germ-cell has twenty-four pairs of chromosomes, one pair being known as the X chromosome and determining sex. It splits into two female gametes of twenty-four corresponding chromosomes, one X chromosome in each gamete. Since the male germ-cell—if I remember rightly—has only twenty-three identical pairs of chromosomes and an additional unmatched pair called the X-Y chromosome, it divides into two male gametes of twenty-four chromosomes each, of which only twenty-three have a twin in each gamete; the twenty-fourth being the X chromosome in one male gamete and the Y chromosome in the other. If a male gamete—or sperm-cell—containing an X chromosome unites with a female gamete—ovum, or egg-cell, the briefing guy called it—carrying an X chromosome, the resultant zygote will be female; but if the Y chromosome gamete fertilizes the ovum, you have a male zygote. They really jammed that stuff in me before they let me leave Earth. Lectures, sleep-sessions, the whole bit.”
“Exactly,” I said enthusiastically. “Now in our case—”
“I recall something else, come to think of it. The Y is supposed to be a slightly undeveloped or retarded chromosome and it makes the gamete containing it a little weaker or something. The sperm-cell with the X chromosome is faster and stronger and has a better chance of fertilizing the ovum. It also shows why women can take it better than men and live longer. Simple. How’s it work with you?”
The extended conversation was making me giddy, and the atmosphere of the dome—with its small vapor content—dried my faculties. However, this was a historic occasion: no personal weakness must be allowed to interfere. I stiffened my tentacles and began.
“After the matrimonial convention, when the chain is established, each sex’s germ-cells are stimulated into meiosis. The germ-cell divides into seven gametes, six of them with cilia and the seventh secreted either inside or outside the Plookh, depending on the sex.”
“What’s this chain?”
“The chain of reproduction. The usually stated order is srob (aquatic form), mlenb (amphibian), tkan (winged), guur (plant-like), flin (a burrower), blap (tree-dweller). And, of course, the chain proceeds in a circle as: srob, mlenb, tkan, guur, flin, blap, srob, mlenb, tkan, guur, flin, blap, srob—”
Hogan Shlestertrap had grasped his head with his hands and was rocking it slowly back and forth. “Starts with srobs and ends with blaps,” he said, almost inaudibly. “And I’m a—”