What is pi, and how did it originate? Succinctly, pi--which is written as the Greek letter for p, or --is the ratio of the circumference of any circle to the diameter of that circle. Regardless of the circle's size, this ratio will always equal pi. In decimal form, the value of pi is approximately 3.14.
Inverted repeat. An inverted repeat (or IR) is a single stranded sequence of nucleotides followed downstream by its reverse complement. The intervening sequence of nucleotides between the initial sequence and the reverse complement can be any length including zero. When the intervening length is zero, the composite sequence is a palindromic sequence.
Word & Letter Play Forward and Backward. A palindrome is a word (or phrase or sentence) that reads the same from left to right as it does from right to left. For example, a palindrome that means trick or joke is gag. For each of the definitions below, suggest a palindrome. 1  Midday. 2  Title for a lady. 3  Tier. 4  Sound a chick makes. 5  Part of the human body. 6  Something that fails to work. 7  An entertainer's short-term job. 8  Short, quick, down-and-up motion. 9  Screwball. 10  Sound a horn makes.