Pronoun problems

pronoun problems

The passage below is from ‘the Blank Slate’ by Steven Pinker.

http://evolbiol.ru/blankslate/blankslate.htm

But the trick may be useless elsewhere in the brain. The olfactory (smell) system, for example, wires itself by a completely different technique. Unlike sights, sounds, and touches, which are arranged by location when they arrive at the sensory cortex, smells arrive all mixed together, and they are analyzed in terms of the chemical compounds making them up, each detected by a different receptor in the nose. Each receptor connects to a neuron ?that carries ?its signal into the brain, and in this case the genome really does use a different gene for each axon when wiring ?them into ?their respective places in the brain, a thousand genes in all. ?It economizes on genes in a remarkable way.

I'd like ask what each underlined pronoun, including one relative pronoun, stands for?
I have my answers. Can you check these out?

? that : a neuron
? it : Each receptor
? them : genes
? their : genes
? It : the genome

Regards.