Complex sentence: The number of vowel phonemes in Tundra Nenets is 10, which have 17 distinct allophones governed by palatality, which dominates whole sequences of vowels and consonants.
Split into simpler sentences: The number of vowels in Tundra Nenets is 10, but 17 if also counting allophones. The allophones are present due to palatality, which dominates whole sequences of vowels and consonants.