Which of the following statements about the expression of genes in the nervous system is true?

Which of the following statements about the expression of genes in the nervous system is true?

Which of the following statements about the expression of genes in the nervous system is true?



  1. Every gene in the human genome is expressed in the CNS.
  2. There are tens of thousands of neuron-specific genes (i.e., genes that are not expressed outside the CNS).
  3. Most of the genes in the human genome are expressed in the CNS.
  4. Humans have 100 times more genes than invertebrate animals such as Drosophila.
  5. Humans have three to four times more genes than mice have.

Answer: 3