Question

There are many different breeds of dogs. The table below gives the average adult size of several of these breeds when individuals are raised in similar environments.

Breed Average Height (inches) Average Weight (pounds)
toy fox terrier 8.5 – 11.5 3.5 – 9.0
Pomeranian 7.0 – 12.0 4.2 – 7.7
Portuguese water dog 17.0 – 22.0 33.0 – 60.0
Irish wolfhound 32.0 – 35.0 115.0 – 180.0
Great Dane 28.0 – 34.0 99.0 – 200.0

Scientists identified a single gene that controls growth in dogs. They found that the Pomeranians and toy fox terriers have similar versions of this gene, but Portuguese water dogs, Irish wolfhounds, and Great Danes have different versions.

Which best explains the findings and the data in the table?
A.
The version of the gene in Pomeranians and toy fox terriers limits growth, so these breeds can only grow to small sizes.
B.
The environment in which the dogs grow changes their genetic material, and these changes affect the dogs' growth.
C.
The difference in size between Portuguese water dogs, Irish wolfhounds, and Great Danes produces different changes in the dogs' genes.
D.
The versions of the gene in Irish wolfhounds and Great Danes decrease the rate at which these breeds grow.

Answer 1

A

Pomeranians and toy fox terriers share the same gene variant and are both small, so that variant likely limits growth to small adult size. The other breeds have different variants and correspondingly larger sizes. Options B and C invoke environment causing genetic change or size causing genetic change (wrong direction), and D contradicts the data (those breeds are larger, not slowed in growth).