Story related and cannot be missed.
There are 7 memories in DNA Sequence 7, 6 of which have optional objectives which completing them during your initial run through will help you with another achievement later on.
Memory 1 - The Hidden City
- Do not get detected
Memory 2 - The Spy Who Shunned Me
- Do not kill anyone
Memory 3 - The Renegade
- Do not let Janos lose more than half his health
Memory 4 - Decommissioned
- Do not take any damage
Memory 5 - Last of the Palaiologi
- Do not take any damage
Memory 6 - Escape
- Do not lose more than half your health
Memory 7 - Passing the Torch
- No optional objective
Once you complete Memory 7, the achievement should unlock.