The manager can do code review if they're a player-manager. If they're a people manager, it's a lot harder to meaningfully review. Managers usually hired in to manage after the team grows (and splits), rather than trying to convert developers into managers, so they may not have a good idea about the code at all.
I'm more inclined to think that it's senior technical responsibility to review, since they'll have a lot more knowledge of the codebase, its evolution and future direction, potential gotchas and various cultural dos and don'ts.
For sure, it's important to keep an eye on the code review culture, though. It's easy for code review to degenerate into nitpicking small things like whitespace, naming, coding conventions - these should be handled by tools instead. And of course if people are being assholes, they need to be pulled up on it.
I'm more inclined to think that it's senior technical responsibility to review, since they'll have a lot more knowledge of the codebase, its evolution and future direction, potential gotchas and various cultural dos and don'ts.
For sure, it's important to keep an eye on the code review culture, though. It's easy for code review to degenerate into nitpicking small things like whitespace, naming, coding conventions - these should be handled by tools instead. And of course if people are being assholes, they need to be pulled up on it.