TLS Online TPP Program

#Question id: 3274


The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?

#Section 3: Genetics, Cellular and Molecular Biology
  1. Postzygotic isolation exists between the two frog species.

  2. Prezygotic isolation exists between the two frog species.

  3. These two species are likely in the process of fusing back into one species.

  4. The hybrids form a separate species under the biological species concept.

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TLS Online TPP Program

#Question id: 3785

#Section 3: Genetics, Cellular and Molecular Biology

The elongation of the leading strand during DNA synthesis

TLS Online TPP Program

#Question id: 3786

#Section 3: Genetics, Cellular and Molecular Biology

E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?

TLS Online TPP Program

#Question id: 3787

#Section 3: Genetics, Cellular and Molecular Biology

A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?

TLS Online TPP Program

#Question id: 3788

#Section 3: Genetics, Cellular and Molecular Biology

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

TLS Online TPP Program

#Question id: 3790

#Section 3: Genetics, Cellular and Molecular Biology

Semiconservative replication of DNA means that:

TLS Online TPP Program

#Question id: 3791

#Section 3: Genetics, Cellular and Molecular Biology

 In vitro systems used to study replication must include all of the following except: