370 Exam 2 QotWeek 6

Among the oldest fossils yet discovered on Earth are microfossils from 600 meters below the Agnes gold mine of South Africa, which are __________ years old.

3.2 billion

Why is the higher fidelity of DNA proofreading and repair (compared to RNA) evolutionarily important?

A lower mutation rate allows for longer genes and more storage of information in the genome.

Itay Budin and Jack Szostak sought to understand how cell membranes composed of single-chain lipid molecules could possibly evolve to the more complex phospholipids seen in modern cell membranes (Budin and Szostak 2009). Which statement best summarizes their results?

Adding a small fraction of phospholipid molecules resulted in vesicles with higher phospholipid content; these cells tended to grow in size conferring a selective advantage.

What do we know about horizontal gene transfer (HGT) in the evolution of early life?

HGT was probably a powerful force during early cell evolution, leading to complex cellular organisms.

In 1977, Sidney Fox tried a different approach to testing the prebiotic synthesis of biological molecules. He mixed a number of different amino acids together at a high temperature (120°C) in an environment lacking water. When he subsequently placed the mixture into water to investigate what the amino acids would form, what happened next?

He found some peptide-like structures, but the bonds between the amino acids were weak and unstable.

Viral genomes tend to be extremely compact due to the effects of strong selection on genome size. Which of the following explains why such a remarkable degree of compression can be achieved?

Multiple genes may be packed into a single region of the genome.

Which of the following is true of the nearly neutral theory of molecular evolution?

Population size plays an important role in determining the outcome of drift and selection.

The first genetic material on Earth was most likely __________.

RNA

According to the neutral theory, most mutations are deleterious and most _______________ are __________.

Substitutions; Neutral

What is the role of telomerase (a protein-based enzyme with an RNA template) in eukaryotic DNA replication?

Telomerase extends the 3' end of a chromosome, adding a specific repeat sequence.

Which of the following statements about the Lincoln and Joyce experiment on self-replicating ribozymes is most likely correct?

The self-replicating ribozymes that had more efficient catalytic activities would soon began to dominate their populations.

Which of the following statements describes the C-value paradox?

There is an enormous variation in genome size across taxa, but organismal complexity does not correlate well with genome size.

Stanley Miller and Harold Urey developed and conducted experimental tests for a "prebiotic soup" model of the origin of life, which had been proposed a few decades earlier by Aleksandr Oparin and J.B.S. Haldane. What did Miller and Urey show could be synthesized abiotically?

amino acids

Which of the following types of prokaryotes are known to have the smallest genomes?

obligate symbiotic bacteria

Small, circular DNA molecules in bacterial cells, which often code for resistance to one or more antibiotics and have the ability to move by the process of conjugation, are called __________.

plasmids

One of the problems in hospitals is that some human pathogens, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria gonorrhoeae, have active mechanisms for acquiring DNA from the environment (which is released when other cells die). Such DNA can subsequently be incorporated into the genome by recombination and confer resistance to multiple antibiotics. This process of gene transfer is known as __________.

transformation

In light of recent achievements in the field of genomics, would it be reasonable to expect that the use of comparative genomics might shed light on the extinct genomes of early life?

Comparative genomics and studies of bacteria with very small genomes shed light on a common ancestor, and researchers can estimate the minimal characteristics that a cell would need to operate as a living organism.

The graph shows the number of nucleotide substitutions in several protein-coding genes and the divergence times for pairs of mammalian species. These data demonstrate which of the following?

Nucleotide substitution rates are approximately constant in these species.

Long interspersed elements (LINEs) make up about 17% of the human genome. What type of transposable elements are they?

retrotransposons

All of the following may be found in prokaryotic genomes except for __________.

spliceosomal introns