State whether the following statements is true/false regarding DNA replication.

1. The polymerization of DNA is essentially irreversible due to the hydrolysis of pyrophosphate.

2. On average about twenty errors are made during each replication of the human genome.

3. DNA polymerase I possesses 5ʹ → 3ʹ exonuclease activity.

4. All DNA ligase enzymes use ATP as a cosubstrate.

5. The purpose of SSB is to prevent single-stranded DNA from folding back on itself to form double-helical regions.

#Question id: 8291

#Unit 9. Diversity of Life Forms

Which of the following pairs are the best examples of homologous structures?

#Question id: 8292

#Unit 9. Diversity of Life Forms

Some molecular data place the giant panda in the bear family (Ursidae) but place the lesser panda in the raccoon family (Procyonidae). If the molecular data best reflect the evolutionary history of these two groups, then the morphological similarities of these two species is most likely due to ________.

#Question id: 8293

#Unit 9. Diversity of Life Forms

The importance of computers and of computer software to modern systematics s is most closely linked to advances in ________.

#Question id: 8294

#Unit 9. Diversity of Life Forms

The common ancestors of birds and mammals were very early (stem) reptiles, which almost certainly possessed three-chambered hearts (two atria, one ventricle). Birds and mammals, however, are alike in having four-chambered hearts (two atria, two ventricles). The fourchambered hearts of birds and mammals are best described as ________.

#Question id: 8295

#Unit 9. Diversity of Life Forms

Imagine that a phylogeny was developed for a group of mammals based on bone structure. Which of the following statements would be a reasonable prediction about a phylogeny for the same group of species based on similarities and differences in the structure of a particular enzyme?

#Question id: 8296

#Unit 9. Diversity of Life Forms

Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species.

According to the phylogenetic tree in the figure above, G. intestinalis constitutes a ________ group.