15-minute activity: Learn the difference between identical and fraternal twins and connect twin studies to genetics vs. environment.
Directions: Read the short intro, then answer the questions.
Monozygotic (MZ) twins (“identical”) form when one fertilized egg splits into two embryos.
Dizygotic (DZ) twins (“fraternal”) form when two different eggs are fertilized by two different sperm.
MZ twins usually have extremely similar genotypes, but they can still differ in phenotype due to environment, development, and epigenetics (chemical tags that affect gene expression).
Twin studies often compare how often a trait is shared by both twins (concordance) in MZ vs DZ pairs.
Two babies come from one fertilized egg that split early in development. What type of twins are they most likely?
Match each term to its best definition.
| Draggable item | arrow_right_alt | Corresponding Item |
|---|---|---|
Epigenetics | arrow_right_alt | Genetic makeup (alleles) |
Concordance | arrow_right_alt | Observable traits |
Genotype | arrow_right_alt | Both twins show a trait |
Phenotype | arrow_right_alt | Gene expression changes without DNA change |
Which observations would be stronger evidence that a trait has a genetic component? (Select two.)
All identical (MZ) twins have identical fingerprints.
In two to three words, what does phenotype mean?
Dizygotic (fraternal) twins are genetically most similar to:
A researcher finds the following concordance rates for a trait:
MZ twins: 80%
DZ twins: 35%
Which conclusion is best supported?