Question

Which of the following could be evidence that an organism's growth is influenced by the organism's genes?

(Hint: Identical twins have identical genes. Non-identical twins have about half the same genes.)

Identical twins often have slightly different weights at birth.
A dog breed can be made smaller by breeding together only the smallest dogs.
Children are likely to have friends who are about the same height.
Identical twins are more likely to be about the same height than non-identical twins.

Answer 1

Evidence for genetic influence:
- A dog breed can be made smaller by breeding together only the smallest dogs.
- Identical twins are more likely to be about the same height than non-identical twins.

Why: Selective breeding shows heritable (genetic) variation for size. Greater similarity in identical twins (who share all genes) versus non-identical twins (who share ~half) indicates a genetic contribution. The other two items point to environmental or social factors rather than genetic effects.