For those wanting to know what the new Snapchat emoji symbols mean, there is several different things that they repersent and these emojis have replaced the âBest Friendsâ feature with Friend Emojis smilies.
(plural tetrads) 1  A group of four things. ( 2 chemistry) A tetravalent atom or radical. ( biology) Two pairs of sister chromatids (a dyad pair) aligned in a certain way and often on the equatorial plane during the meiosis process.
Quick Answer. Tetrads, also known as bivalents, form during the prophase 1 stage of meiosis when duplicated chromosomes, each composed of two identical chromatids, pair up and complete the process of crossing over in which one chromosome exchanges corresponding segments of genetic material with the other chromosome in the tetrad.