1. We compared 282 randomly chosen polymorphic PCR-based DNA markers in three pl
ID: 69744 • Letter: 1
Question
1. We compared 282 randomly chosen polymorphic PCR-based DNA markers in three plant species of the same genus, Amaranthus cruentus, A. caudatus, and A. hypochondriacus. These three species are difficult to classify morphologically. We found that A. hypochondriacus and A. caudatus had 137 markers in common (i.e. 145 markers differed genetically when the two species were compared), A. hypochondriacus and A. cruentus had 73 markers in common, and A. caudatus and A. cruentus had 72 markers in common. According to this analysis, which two species are most closely related?
2. The interfertility of the same three species of Amaranthus described above in problem #1 was tested. Large number of F1 hybrids between A. hypochondriacus and A. cruentus could be produced when the two
species were hybridized. These hybrids had low pollen fertility. Attempts to hybridize A. caudatus and A. cruentus generated only a few F1 plants most of which died as seedlings. The few survived were sterile.
According to this analysis, which two species are most closely related? How does this information correspond with the information in problem #1? What types of reproductive isolation are evident from this information?
8. The three species of Amaranthus described in problems #5 and #6 were cultivated as food crops by ancient American civilizations. They do not grow well as wild plants. A. hypochondriacus was grown anciently from the southwestern United States into central Mexico. A. cruentus was grown anciently in northern and central Mexico (where its cultivation overlapped that of A. hypochondriacus) into Central America. Ancient cultivation of A. caudatus was confined to the Andes mountains of South America. What does the information from questions #1 and #2 suggest about the geographical dispersal of these three species of Amaranthus?
Please answer ALL THREE questions completely and I will be sure to "thumbs up" your response! Thank you!
Explanation / Answer
1. According to the data, the two plants whcih have the most markers in common are the most related.
2. In this part of the question, a cross between A. hypochondriacus and A. caudatus is missing. From the other two crosses, we can say that the cross which produced F1 in large numbers are closely related. The relation to the info in question 1 would be that more number of common markers are needed to get a good fertile progeny in F1. The two types of reproductive isolation seen are low pollen fertility and steril progeny.
3. The info from the first two questions indicate that pairing has never occured outside the species. The species have been practising reproductive isolation which has not allowed any useful hybrids to come up. This shows that the species are probably far from each other geographically.
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