Corrected entry: We all know that Raven's left leg is amputated, but at the point she and Shaw lay in bed, her left leg is fine.
Corrected entry: When Clarke gets to Becca's lab, her mom asks where the others are. She says that they are unloading the rover, but they got there by boat.
Correction: She's asks "where's Roan" (not about the others) and Clarke says "he's unloading fuel with the others."
Corrected entry: If night-blood is passed parent to child, there's no way for them to exist as all night-bloods die in conclaves before child bearing age.
Correction: S5E1. Clark tells Madi: "Until I figure this out, I want you to hide in your secret spot. This is not up for discussion, Madi. The Flamekeeper scouts never found you there. Neither will they." This indicates that there were probably more nightbloods that never got found, therefore they could have passed it down to their children.
I don't think it acts like this, I think it's more so everyone has the nightblood gene, it just doesn't show in everyone - like the redhead gene.
Correction: In no episode was Raven's leg ever amputated. She wore a knee brace because she had unhealing nerve damage from the knee down, but can still move her upper leg.