mod2 exam

Pax-6 usually causes the production of a type of light-receptor pigment. In vertebrate eyes, though, a different gene (the rh gene family) is responsible for the light-receptor pigments of the retina. The rh gene, like Pax-6, is ancient. In the marine ragworm, for example, the rh gene causes production of c-opsin, which helps regulate the worm's biological clock. Which of these most likely accounts for vertebrate vision?

During vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments.

Which of the following statements correctly describes the lysogenic cycle of lambda (λ) phage?

The phage genome replicates along with the host genome.

Which of the following responses correctly lists the order of events in a generalized viral replicative cycle?

The virus enters the cell, host enzymes replicate the viral genome, enzymes transcribe the viral genome into mRNA.

A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?

The plants would develop the typical symptoms of TMV infection.

What is one key difference between genetic transformation and transduction in prokaryotes?

Transformation involves the uptake of foreign DNA from the surroundings, whereas transduction involves a virus transferring DNA from one bacterium to another.

Which of the following statements correctly describes adenoviruses?

They contain DNA surrounded by a capsid.

Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two "strategies" that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?

be obligate anaerobes and package these enzymes in specialized cells or compartments that inhibit oxygen entry

During the Cambrian explosion, fossil evidence indicates a rapid and sudden diversification of more complex animals. However, fossils of Ediacaran animals from 30 million years prior to this demonstrate that genes to produce complex animals had already existed. What could explain this?

changes in the environment that brought about selective adaptations and evolution during the Cambrian, repurposing some gene regions through differential regulation

Thiobacillus ferrooxidans is a type of bacteria that oxidizes iron compounds for energy and then uses that energy to build carbohydrates. We might best recognize this bacterium as the rust-colored ring that builds up inside toilet bowls. Thiobacillus ferrooxidans is an example of a

chemoautotroph.

If a bacterium regenerates from an endospore that did not possess any of the plasmids that were contained in its original parent cell but does contain the large circular chromosome, the regenerated bacterium will probably also

lack antibiotic-resistant genes.

Scientists have identified two major branches of prokaryotic evolution. What was the basis for dividing prokaryotes into two domains?

genetic characteristics such as ribosomal RNA sequences

This bacterium's ability to survive in a human who is taking penicillin pills may be due to the presence of which of the following? 1. penicillin-resistance genes 2. a gram-positive cell wall 3. a gram-negative cell wall 4. an endospore

3 and 4

Which of the following statements correctly describes one characteristic of the lytic cycle of viral replication?

A large number of phages are released at a time

Scientists, looking at the range of beak shapes and sizes across different finch species, observed that the thicker beak expressed a gene known as BMP4 early in development. To verify that the BMP4 gene itself could trigger the growth of bigger beaks, researchers increased the production of BMP4 in the developing beaks of chicken embryos. Which of the following results would explain why BMP4-treated chicks began growing wider, taller beaks?

BMP4 is a homeotic gene.

In sexually reproducing lizards, recombination and meiosis result in offspring that have a variety of genetic material from both parents and high genetic diversity in the population. In contrast, what is one key way in which genetic diversity arises in non-sexually reproducing bacteria

Bacteria typically form populations with high numbers of individuals, and combined with rapid generation times, this may lead to a high rate of genetic mutations.

What is a main difference between endotoxins and exotoxins?

Endotoxins are lipopolysaccharides and thus structurally integral to the bacterium, whereas exotoxins are proteins that are secreted by living bacteria.

What should be true of the cell wall of this bacterium?

It has an outer membrane of lipopolysaccharide.

The thermoacidophile Sulfolobus acidocaldarius lacks peptidoglycan but still possesses a cell wall. What is likely to be true of this species?

It is an archaean that could inhabit hydrothermal vents if the optimal pH of its enzymes lies below pH 7.

Which of the following is an important source of endotoxin in gram-negative species?

cell wall

Some people who have had a herpesvirus-mediated cold sore or genital sore may have flare-ups for the rest of their life. Why does this occur?

copies of the herpesvirus genome remaining as mini-chromosomes in some host cell nuclei

Plantlike photosynthesis that releases O 2 occurs in

cyanobacteria

The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can then reactivate, replicate again, and be infectious to others. If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection?

interference with new viral replication in preexisting cases

If these fly species lost the ability to fly independently of each other as a result of separate mutation events in each lineage, then the flightless condition in these species could be an example of

species selection.