Wild type E. coli metabolizes the sugar lactose by expressing the enzyme ß-galactosidase. You have isolated a mutant that you call lac1–, which cannot synthesize ß-galactosidase and cannot grow on lactose (Lac–). During an condition Lac– strain, called lac3–, is linked to the Tn5 insertion. From a strain carrying the Tn5 insertion and lac3– mutation you isolate an F’ that caries a region of the chromosome that includes both Tn5 and the linked Lac region. Introduce this F’ into an F– strain carrying lac1– by selecting for Kanr. These merodiploids express ß-galactosidase normally. What does this result tell you about the relationship between the lac3– and lac1- mutations?  

#Question id: 4973

#SCPH28 | Zoology

Fossils of Lystrosaurus, a dicynodont therapsid, are most common in parts of modern-day South America, South Africa, Madagascar, India, South Australia, and Antarctica. It apparently lived in arid regions, and was mostly herbivorous. It originated during the mid-Permian period, survived the Permian extinction, and dwindled by the late Triassic, though there is evidence of a relict population in Australia during the Cretaceous. The dicynodonts had two large tusks, extending down from their upper jaws; the tusks were not used for food gathering, and in some species were limited to males. Food was gathered using an otherwise toothless beak. Judging from the fossil record, these pig-sized organisms were the most common mammal-like reptiles of the Permian.Which of Lystrosaurusʹ features help explain why these organisms fossilized so abundantly?

I. the presence of hard parts, such as tusks

II. its herbivorous diet

III. its persistence across at least two geological eras

IV. its widespread geographic distribution

V. its mixture of reptilian and mammalian features

#Question id: 4974

#SCPH06 I Botany

Which of these is the most likely explanation for the modern-day distribution of dicynodont fossils?

#Question id: 4974

#SCPH28 | Zoology

Which of these is the most likely explanation for the modern-day distribution of dicynodont fossils?

#Question id: 4975

#SCPH06 I Botany

The observation that tusks were limited to males in several species, and were apparently not used in food-gathering, is evidence that the tusks probably

#Question id: 4975

#SCPH28 | Zoology

The observation that tusks were limited to males in several species, and were apparently not used in food-gathering, is evidence that the tusks probably

#Question id: 4976

#SCPH28 | Zoology

Which of these is the most likely explanation for the existence of dicynodont fossils on modern-day Antarctica?