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: 3838

#Unit 3. Fundamental Processes

Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA during DNA replication?

#Question id: 3839

#Unit 3. Fundamental Processes

Use the figure to answer the following question. In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" (radioactive) nitrogen (15N) and then transferred them to a medium containing 14N (nonradioactive). Which of the results in the figure would be expected after one round of DNA replication in the presence of 14N?

#Question id: 3840

#Unit 3. Fundamental Processes

The mechanism of DNA replication is studied in an E. coli replication fork. When will this fork stop replicating DNA?

#Question id: 3841

#Unit 3. Fundamental Processes

The DNA replication occurs in a semi-conservative manner which means

#Question id: 3842

#Unit 3. Fundamental Processes

Which of the following statements correctly describes the difference between the leading strand and the lagging strand in DNA replication?

#Question id: 3843

#Unit 3. Fundamental Processes

In DNA replication in E. coli, the enzyme primase is used to attach a 5 to 10 base ribonucleotide strand complementary to the parental DNA strand. The RNA strand serves as a starting point for the DNA polymerase that replicates the DNA. If a mutation occurred in the primase gene, which of the following results would you expect?