Measuring Inheritance Over Time and in Twins
Take the reading one piece at a time. For each piece: read it once, underline the sentence that says what happens, then look up any word in the list. Tap a word to see its definition.
Piece 1 of 2
A cohort study reverses the case-control arrow. Instead of starting with the outcome, it starts with the exposure and follows people forward. Imagine enrolling two groups of pregnant women at the start of pregnancy, one with a chosen exposure and one without; no one has had their baby yet. You follow every pregnancy forward and record which babies are born with a cleft. Because you measured the exposure before any outcome existed, no one can misremember it. The catch: clefts are rare, about 1 in 700 births [DOI:10.1002/bdr2.2216], so a forward cohort must be very large and patient.
Piece 2 of 2
Researchers linked a national cleft database to a national twin registry, verified which pairs were identical versus fraternal, excluded syndromes, and asked: when one twin has a cleft, how often does the other also have one (the concordance) [PMID:21423016]? Identical (monozygotic) twins share nearly 100 percent of their DNA; fraternal (dizygotic) twins share about 50 percent, like any siblings, and both kinds share a womb at the same time. Their results for cleft lip with or without cleft palate: identical twins 50 percent concordance, fraternal twins 8 percent. From models like this, the study estimated heritability above 90 percent for clefting [PMID:21423016].
Reading the Research
- Skim the title and abstract first to get the gist.
- Circle the one sentence that states the main claim.
- Box the evidence the authors give for that claim.
- Mark one sentence that confuses you, and move on.
Now put it together: In one or two sentences, say what this whole reading is telling you about Mateo. Then go back to the lesson and fill in the guided notes.