Biology Final Exam Review 5

Which is an example of a response of the immune system to attack a specific pathogen?

• A blood clot forms after the skin is cut or scraped.

• Stomach acid kills bacteria that are swallowed along with food.

• Antibodies bind to antigens on the surface of bacteria.

• A cell makes viral proteins after viral DNA has been injected into it.

A virus called HIV causes AIDS, a deadly disease. How is an HIV infection different from infections of other, less harmful viruses?

• HIV injects its DNA into a human cell.

• HIV attacks cells of the immune system.

• HIV takes over cell mechanisms very quickly and is never dormant.

• HIV attacks cells of the respiratory system and circulatory system.

A gardener crosses a true-breeding tall tomato plant bearing red fruit with a true-breeding dwarf tomato plant with yellow fruit. In tomatoes, tall vine (T) is dominant to dwarf vine (t) and red fruit (R) is dominant to yellow fruit (r).

Assume that the two genes controlling the "tall vine" and "red fruit" traits are on two different pairs of chromosomes.

What are the expected phenotype ratios in the F2 generation?

• 9 tall vine/red fruit; 3 tall vine/yellow fruit; 3 dwarf vine/red fruit; 1 dwarf vine/yellow fruit

• 4 tall vine/red fruit; 3 tall vine/yellow fruit; 1 dwarf vine/red fruit

• 2 tall vine/red fruit; 4 tall vine/yellow fruit; 2 dwarf vine/yellow fruit

• 16 tall vine/red fruit; 9 tall vine/yellow fruit; 3 dwarf vine/red fruit; 1 dwarf vine/yellow fruit

A plant's stem lengths were graphed from the F1 generation. Seven categories of stem length phenotypes were observed.

What pattern of inheritance is suggested by the graph?

• codominance

• multiple alleles

• polygenic inheritance

• incomplete dominance

Western and Eastern meadowlarks look very similar and it is difficult to tell them apart, until they sing. Their mating songs are quite different. The Western meadowlark has a melodious song, whereas the song of the Eastern meadowlark sounds more like a whistle. Even though their ranges overlap in the central United States, they do not interbreed and are two different species. How would speciation most likely have occurred in these two species of meadowlarks?

• Reproductive isolation occurred through behavioral isolation.

• Reproductive isolation occurred through temporal isolation.

• Populations were separated through geographical isolation.

• Populations were separated through competition.

Corn plants cannot be separated into discrete types or classes by their height.

What does the graph show?

• The graph shows the distribution of polygenic phenotypes that are expected for a trait in which two or more genes contribute to the trait.

• The graph shows the distribution of corn plants from a monohybrid cross.

• The graph shows the distribution of corn plants from a dihybrid cross.

• The graph shows the distribution of single-gene phenotypes that are expected for a trait in which two or more dominant alleles control the trait.

A geneticist collected data of a population of mice. Of the 50 mice, 12 were homozygous black (BB), 24 were heterozygous black (Bb), and 14 were brown (bb).

What are the allele frequencies for the (B) and (b) alleles in this population?

• B = 0.32; b = 0.68

• B = 0.36; b = 0.64

• B = 0.48; b = 0.52

• B = 0.45; b = 0.55

Study the graph to see how grasshoppers of three different body colors survive predation by blue jays in a mostly green environment. Grasshopper numbers are shown before and after blue jays preyed on them.

Which statements are supported by the data in the table? Choose three correct answers.

• If brown grasshoppers are more visible to blue jay predators in green environments, they might be less likely to reproduce, and the allele for brown color will be become less common.

• If green grasshoppers are less visible to blue jay predators in green environments, they will be more likely to reproduce, and the allele frequency for green color will increase.

• If natural selection produces changes in the allele frequencies of yellow-green grasshoppers in the green environment, there will be fewer of them.

• If grasshoppers avoid an environment that matches their body color, they will be more likely to survive and reproduce successfully.

Incomplete dominance in snapdragons produces three phenotypes: red flowers (RR), white flowers (R'R'), and pink flowers (RR'). A population of snapdragons was determined to have eggs and sperm with the following allele frequencies: 0.25 (R) and 0.75 (R').

Use the Hardy-Weinberg equation (p2 + 2pq + q2 = 1 and p + q = 1) to determine the flower color phenotype frequencies in the offspring of this population.

• Red flowers = 0.0625; Pink flowers = 0.375; White flowers = 0.5625

• Red flowers =0.375; Pink flowers = 0.0625; White flowers = 0.5625

• Red flowers = 0.25; Pink flowers = 0.50; White flowers = 0.25

• Red flowers = 0.225; Pink flowers = 0.625; White flowers d = 0.150

The molecular clock hypothesis states that DNA and protein sequence differences between any two species is proportional to the time since these species last shared a common ancestor.

How do molecular clocks mark time?

• Molecular clocks mark time by mutations that tend to accumulate at the same rate in different species.

• Molecular clocks mark time by DNA or protein sequence changes at a rate of 1% per 1 million years.

• Molecular clocks mark time at a mutation rate of 2% per 5 million years.

• Molecular clocks mark time by major mutations that are under natural selection pressure at different rates in different species.