What's the distinction between a tetrad and a synaptonemal complex in meiosis? What's the distinction between a tetrad and a synaptonemal complex in meiosis? Are they synonyms? I ask because the concepts seem very closely related, but it seems like there may be a subtle distinction. Unfortunately, none of the sources I've been consulting use both terms.

As far as I can tell there _is_ a distinction.

A **tetrad** refers to the _entire_ group of four chromatids after they have come together for crossing over in Prophase I (synapses).

A **synaptonemal complex** as you would expect is formed in synapses. This is a protein-RNA complex that connects the intervening regions of matched chromosomes in some circumstances - it is not required. Mutated yeast that can not form this complex has still been shown to be able to exchange genetic information.

In other words, **you can have a tetrad without a synaptonemal complex, but not vice versa**.