1. George Beadle concluded that teosinte is the likely ancestor of maize (corn) even though the two plants appear very different. What evidence did Dr. Beadle collect that led to his conclusion? Select all that apply.

1. Teosinte and maize have similar chromosomes.
2. Both teosinte and maize have one main stalk.
3. Both teosinte and maize have naked, soft kernels.
4. Teosinte and maize can produce fertile hybrids.

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2. Dr. Beadle crossed teosinte and maize to produce F1 offspring. He then crossed those plants to produce an F2 generation. The table below shows the expected phenotype ratios for the F2 plants.

Dr. Beadle planted 50,000 F2 seeds. When the offspring of these F2 seeds grew, about 100 looked like teosinte and about 100 looked like maize. Based on this result, how many genes did Dr. Beadle conclude could account for the differences between maize and teosinte?

1. Three
2. Three or four
3. Four
4. Four or five

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3. Dr. Doebley and his team compared the DNA sequence of maize to that of a number of teosinte varieties from throughout Mexico. What did their analysis reveal? Select all that apply.

1. That teosinte and maize have the same number of chromosomes.
2. That maize originated from a variety of teosinte that existed about 9,000 years ago.
3. That maize and teosinte could interbreed to produce viable hybrid plants.
4. That maize is most closely related to a teosinte variety in the Balsas region of Mexico.

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4. Scientists working in the fields of both genetics and archaeology have made discoveries that help us understand the origin of maize. In which way(s) did each discipline's work support evidence generated by the other? Select all that apply.

1. Genetics data pinpointed the likely location of the earliest maize domestication, which allowed archaeologists to find fossil evidence of early maize in caves.
2. Geneticists used DNA data to determine how long ago maize was domesticated. Archaeologists then verified the conclusion by dating maize microfossils.
3. Archaeologists determined where maize was first domesticated. Afterward, geneticists verified the conclusion and calculated how long ago that domestication took place.
4. Geneticists used archaeological data to identify how many genes controlled the changes from teosinte to maize.

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5. Teosinte kernels are covered in a hard fruitcase, whereas maize kernels are "naked." What happened when Dr. Doebley's team introduced maize's version of the fruitcase gene into teosinte plants?

1. The teosinte kernels became enclosed in an even tougher fruitcase.
   
2. The teosinte plants that resulted looked like maize in every feature.
   
3. The teosinte plants had two kinds of kernels, some with no fruitcase at all and some with an intact fruitcase.
   
4. The teosinte kernels were partially exposed.

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6. In what situation can changes in just a few genes dramatically change an organism's entire appearance?

1. When an organism has only a few genes.
2. When the genes control the expression of many other genes.
3. When all of the organism's genes have big effects on phenotype.
4. When the genes are each thousands of nucleotides long.

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