meem like theme, scheme, extreme, supreme

meem. I got shocked to know this as well. :/

While English spelling isn't very consistent, "meme" IS pronounced exactly as it's spelled. The rule that a single "e" after a single consonant lengthens the vowel before the consonant, so "meme" is pronounced "meem". Other words also follow this rule, such as "make", "hate", "site", "bite", "dote", "fire", etc. Of course, English being English, there are exceptions to this rule. "One" would logically be pronounced like "own", but it's actually pronounced like "wun". You'd expect "done" to rhyme with "dome", but it's actually pronounced "dun". A single 'e' at the end of a word on its own is almost never pronounced in English, except in some loanwords e.g. "cafe". The only word I can think of where a single "e" makes its normal sound (as in "red") at the end of a word is in one of the two pronunciations of "the".

The word "meme" was coined by evolutionary biologist Richard Dawkins as a counterpart to "gene." Genes are a biological mechanism that carries characteristics from generation to generation; memes are ideas and behaviors that spread from person to person and culture to culture and thus represent a different kind of evolutionary mechanism. In addition to the reasons given by others, I think that the word was intended to be a matching pair with "gene," and thus both are pronounced with a long "e" in the middle and a silent "e" at the end.

Thanks! Too bad I lost :D