What the underlined words refer to?

What the underlined words refer to?

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

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

A promising example is the F0XP2 gene, associated with a speech and language disorder in a large family. The aberrant nucleotide has been found in every impaired member of the family (and in one unrelated person with the same syndrome), but it was not found in any of the unimpaired members, nor was it found in 364 chromosomes from unrelated normal people. The gene belongs to a family of genes for transcription factors — proteins that turn on other genes — that are known to play important roles in embryogenesis.


In this passage I want to know what the two underlined words refer to.
Let me tell you my answer first.
The former, ‘proteins,’ seems to represent ‘a family of genes.’
I’m quite sure about this but I want to double check.

The latter one is quite tricky.
It seems to stand for ‘the gene’ in one way and be able to refer to ‘a family of genes’ in another.
Hope for your reply to get me out of this dilemma.

Regards.