Correct! Both teosinte and maize have 10 pairs of chromosomes, and each pair in one species is very similar to a pair in the other species. Select another correct answer. You selected all the correct answers.

Teosinte plants are bushy, with multiple stalks. Maize, on the other hand, has a single main stalk supporting the plant. Try again.

Maize has naked, soft kernels, but teosinte fruitcases are so hard you could "crack your tooth" if you tried to eat them. Try again.

Correct! Dr. Beadle was able to cross maize and teosinte plants to produce hybrid plants that could themselves be crossed to produce another generation. Select another correct answer. You selected all the correct answers.

If three genes are responsible for the differences between teosinte and maize, about 1 in 64, or (1/64 × 50,000) = 781 total plants should have looked just like teosinte, and another 781 plants should have looked just like maize. Try again.

If three or four genes are responsible for the differences between teosinte and maize, between 1 in 64 (1/64 × 50,000) = 781 and 1 in 256 (1/256 × 50,000) = 195 plants should have looked just like teosinte or maize. Try again.

If four genes are responsible for the differences between teosinte and maize, about 1 in 256, or (1/256 × 50,000) = 195 total plants should have looked just like teosinte, and another 195 plants should have looked just like maize. Try again.

Correct! Dr. Beadle predicted that if four genes are responsible for the differences between teosinte and maize, about 1 in 256, or (1/256 × 50,000) = 195 total plants should have looked just like teosinte. If five genes are responsible for the differences, about (1/1024 × 50,000) = 49 total plants would look like teosinte. His result of about 100 of the 50,000 plants looking just like teosinte falls between these two values, suggesting that four or five genes are involved. Select another correct answer. You selected all the correct answers.

Scientists knew that maize and teosinte have the same number of chromosomes before they sequenced DNA. Try again.

Correct! Using the rate of mutations and the differences between teosinte and maize genomes provides a way to estimate the time since lineages have diverged. Select another correct answer. You selected all the correct answers.

Scientists knew that maize and teosinte could be crossed even before they looked at their DNA. Try again.

Correct! By comparing the maize genome to the genomes of various teosinte varieties, Dr. Doebley's team discovered that maize was most similar genetically to the Balsas teosinte population. Select another correct answer. You selected all the correct answers.

Correct! Based on Dr. Doebley's conclusions, archaeologist Dr. Dolores Piperno and her team were able to limit their search for fossil evidence of maize domestication to a particular area of Mexico. Select another correct answer. You selected all the correct answers.

Correct! Based on genetics, Dr. Doebley's team had estimated that maize was first domesticated 9,000 years ago. By using radiocarbon dating of charcoal found with maize microfossils, Dr. Piperno and her team came up with a very similar estimate for maize domestication: 8,700 years ago. Select another correct answer. You selected all the correct answers.

Dr. Doebley, a geneticist, got the first clue that maize originated from the Balsas region in Mexico. Try again.

Dr. Beadle determined that between four and five genes were involved in controlling the differences between teosinte and maize using genetic crosses. Try again.

The maize fruitcase gene modifies the seed coat of the teosinte offspring to look more like maize. Try again.

The gene that was inserted into the teosinte plant mainly affected the fruitcase, not the other traits that differ between the species. Try again.

When the fruitcase gene is expressed, it affects all of the kernels on a given cob. Try again.

Correct! Teosinte engineered to express the maize fruitcase regulatory gene produces seeds that are only partly covered with a fruitcase. Select another correct answer. You selected all the correct answers.

Teosinte has thousands of genes, yet changes in a small number of genes are responsible for the transformation to maize. Try again.

Correct! Changes to regulatory genes, which can control the expression of hundreds of other genes, can generate dramatic changes in an organism's overall phenotype. Select another correct answer. You selected all the correct answers.

All genes contribute to phenotypes, but phenotype is about more than outside appearance. Blood type is a phenotype, for example, and it doesn't affect how a person looks. Only certain kinds of genes have a big effect on an organism's outward appearance. Try again.

The length of a gene does not correlate with its effect on an organism's phenotype. Try again.