Enrollment in Math 100 is not a prerequisite for any math class. It is the final exam for these classes which places you into your next math class. You must take your final exam and score sufficiently high to place into your next math class.
Final exam/placement scores are loaded into the system within 3-5 business days of taking the final exam. You will be able to register for whatever class you are eligible for once your score is posted to the system. You can check the status of your posting at http://math.arizona.edu/academics/placement/exams/scores (if your Math 100 score is posted, you'll see an MCLG score, and approximate date of your final exam).
The one exception to this rule is during the last two business days of Freshmen Priority Registration. We open up the registration to Math 112 for students enrolled in Math 100 at 8:00am on the Thursday of this week and close it down at 3:00pm on the Friday. During this time, Math 100 students are able to add Math 112 to their schedule via UAccess. Non-freshmen may visit the staff in room 108 of the Math building during these two days only to add Math 112, as this is not their week to register through UAccess. If the student does not pass the Math 100 final sufficiently for enrollment in Math 112, (s)he will be dropped.