Dizygotic Twins

by Greg Crowther

As most people know, twins can either be identical (monozygotic) or fraternal (dizygotic). This brief song focuses on the latter.

Oocyte release
Sometimes gets increased....
Dizygotic! Somewhat predictable.
Dizygotic! They're rare but plausible.
Dizygotic! Most often siblings full.
Dizygotic! But not identical.
Two sperm meet two eggs....
Four arms and four legs....
Somewhat predictable.
They're rare but plausible.
Most often siblings full.
But not identical.
Dizygotic!

• sheet music (with melody play-back)

Songs like this one can be used during class meetings and/or in homework assignments. Either way, the song will be most impactful if students DO something with it, as opposed to just listening.

An initial, simple follow-up activity could be to answer the study questions below. A more extensive interaction with the song might entail (A) learning to sing it, using an audio file and/or sheet music as a guide, and/or (B) illustrating it with pictures, bodily poses, and/or bodily movements. The latter activity could begin with students identifying the most important or most challenging content of the song, and deciding how to illustrate that particular content.

(1) What is polyovulation, and what does it have to do with dizygotic twins?

(2) The song refers to dizygotic twins as "rare but plausible" and "somewhat predictable" because certain parents are more likely to have dizygotic twins. Is this genetic predisposition associated with mothers, or with fathers?

(3) What are full siblings, as opposed to half siblings? Explain why dizygotic twins are "most often [but not always] siblings full."

(4) Is there a difference between "oocyte" and "egg"?