The minor chord resembles the major chord except that it has a minor third with a major third on top, while a major chord has a major third with a minor third on top. They both contain fifths because two pitches a major and minor third apart are a fifth apart.
A major chord in just intonation is tuned to the frequency ratio 6:5:4, while in equal temperament it has 3 semitones between the third and fifth, 4 between the root and third, and 7 between the root and fifth. It is represented by the integer notation 0,4,7. In equal temperament, the fifth is only two centss narrower than the just perfect fifth, but the major third is noticeably different at 13.686 wider.