What is the ultimate source of genetic variation

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Question

1. The basic reproductive number for an infectious disease in a population, R0, describes:

(A) The probability that an infected individual will transmit the disease to a susceptible individual, when necessary contact is made.

(B) The average number of susceptible individuals to whom each infected individual transmits the disease.

(C) The average length of time an infected individual can transmit the disease to a susceptible individual before recovering or dying.

(D) The percent of the total population that will ever become infected with the disease.

2. A new disease has emerged in an isolated community of 500 people. You have been asked to determine whether it is likely to cause an epidemic. After some research, you determine the infectious period (L) to be 2 days and the transmission rate (β) to be 0.003 per day. Will an epidemic occur in this community? Why or why not?

(A) Yes, because R0>1

(B) Yes, because R0<1

(D) No, because R0<1

3. What factor of R0 is affected by vaccination, and how?

(A) Vaccination reduces the average infectious period (L).

(B) Vaccination reduces the initial number of susceptible individuals (S).

(D) Vaccination removes potential vectors from the environment.

4. The basic reproductive number, R0, describes the average number of individuals in a fully susceptible population that an infected individual will infect. Which of the following changes would cause an increase in R0?

(A) A decrease in the infectious period, L.

(B) An increase in the transmission rate, β.

(D) An increase in the initial number of infected individuals, I.

5. Although established vaccines (such as those for measles and influenza) are safe and effective for most people, there are individuals who should not be vaccinated. For example, people with AIDS, cancer, type I diabetes, or other health conditions may have weakened immune systems and often cannot be safely vaccinated. How can vaccines help protect these individuals?

(A) Individuals who are not vaccinated are protected if enough members of their community are vaccinated so that the disease cannot spread.

(B) If enough people are vaccinated, the disease will be forced to evolve and individuals who were not vaccinated will be protected.

(C) Vaccines cannot help people with weak immune systems. Each and every person must be vaccinated if they are to be protected from the disease.

(D) Resistance can spread through direct contact, allowing unvaccinated individuals to gain immunity by interacting with those who have been vaccinated.

6. Which of the three groups will have a curve that ONLY increases as time progresses?

(A) S, the number of susceptible individuals.

(B) I, the number of infected individuals.

(D) Both the number of recovered individuals (R) and the number of infected individuals (I).

7. Which of the three curves in an SIR model is hump-shaped?

(A) Susceptible

(B) Infected

(D) Vaccinated

8. A population experiences an outbreak of a disease that none of its members have previously been exposed to. Immediately before the disease is introduced (that is, at time=0), to which SIR group do all members of the population belong?

(A) S, the number of susceptible individuals

(B) I, the number of infected individuals

(D) Sometimes S and sometimes R

9. When pathogens like viruses reproduce, they must copy their genetic code-their DNA or RNA. During this process mistakes are sometimes made, producing a new sequence of RNA or DNA that is slightly different. These copying errors are an example of what?

(A) Evolution by natural selection

(B) Genetic drift

(D) Mutation

10. What is the ultimate source of genetic variation?

(A) Evolution by natural selection

(B) Genetic drift

(D) Mutation

11. Evolution is a change in the genetic composition of a population over time. Sometimes this change is driven by random chance-by luck. For example, imagine that two students-roommates-both contract the flu. Before either knows they are sick, the flu quickly mutates in one student who then wins the lottery and uses the money to travel to Boca Raton for spring break. While there, he infects hundreds of other students enjoying their time in the sun. Meanwhile, the other student spends his spring break in an empty dorm and sees no one before recovering. In some sense, the student who went to Florida is not the only one who won the lottery. The strain of the virus infecting him won, too, because his random luck let the virus spread more widely. What is it called when these sort of chance events drive evolutionary change?

(A) Evolution by natural selection

(B) Genetic drift

(D) Mutation

Reference no: EM133933414

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