What would the doctoral student say is his rationale for including the chicken DNA in his homology analysis?
The Coughing Frog
Carl Kauffeld was a world-renowned and well-respected expert in Reptile and Amphibian biology. In 1937, he was doing
a field study in rural Connecticut when he heard an unusual noise. In his notes, he recorded that he heard a number of
coughs from the swamp he was in. He feared he had stumbled upon a pond full of sick frogs. He was able to scoop up
one of the coughing frogs and brought it to his lab to study. As it turned out, his new little friend was not sick, but
instead had a unique new mating call or “croak” that had not been catalogued or heard before.
Since a female of a particular frog species will only mate with a male who emits the correct croak, it was obvious to
Kauffeld that he had discovered a new species of amphibian. He wanted his coughing frog to be recognized as such.
His colleagues counterclaimed that it was not its own species, but instead was a mutated member of either the
Southern or Northern Leopard frog family. Kauffeld had no other evidence to show, so the idea of the little frog getting
his own scientific name was dropped.
Flash forward to today and the coughing frog is back in the news. He has been re-discovered in State Island by a
doctoral student who believes he has the proper evidence to prove the little guy indeed deserves his own genus and
Use the passage below, as well as the original reading, to answer this question.
Scientists use a number of pieces of evidence to determine if an organism should be classified as its own species. These pieces of evidence almost always include making comparisons between the new organism and other species who are similar to the new organism. One such comparison can be made by looking at DNA sequences between organisms, scientists can not only determine species origin, but they can also determine how closely related species are and gather knowledge about an organisms evolutionary history.
The doctoral student has drawn blood samples from each of five organisms: The coughing frog, a Northern Leopard Frog, a Southern Leopard Frog, the American Bullfrog, and a chicken. Using the latest in automated techniques, he sequenced DNA from an area in the first chromosome from each organism. Using a sophisticated database, he was able to compare the sequences of each of the species to the others. The goal of the comparison was to show the per cent homology (likeness) between the sequences. The results of the comparison are shown in the chart below:
Per Cent Homology between DNA Sequences Taken From Chromosome #1 Blood Samples
|Organism||Coughing Frog||NOrthern Leopard Frog||Southern Leopard Frog||Bullfrog||Chicken|
|Northern Leopard Frog||92||100||93||74||16|
|Southern Leopard Frog||88||93||100||72||18|