Q1) The graph on the right shows the proportion of snails from different clonal
ID: 70461 • Letter: Q
Question
Q1)The graph on the right shows the proportion of snails from different clonal strains infected by a parasite. The first four bars are from four distinct and relatively common clonal strains. The fifth bar is an average infection rate for 40 rarer strains. Imagine one of the rare snail strains with a low infection rate actually reproduces sexually. What would you expect to happen over time?
Q2) Now say you repeated the experiment but added a drug that killed all the parasites. What would you expect to happen over time?
Options for both questions are:
A)The sexual population will stay rare or go extinct because the asexually reproducing snails can reproduce more quickly.
B)The sexual population will first grow, while it is relatively rare, but then shrink and likely go extinct after it becomes common, because once it is common it will be attacked by parasites more frequently.
C)The sexual population will grow until it is more common than all the clonal populations, because it can more quickly evolve new protection from parasites.
Explanation / Answer
1) The correct answer is option C.
C)The sexual population will grow until it is more common than all the clonal populations, because it can more quickly evolve new protection from parasites.
When the experiment is done, then the sexual population will grow until it is more common than all the clonal populations, because it can more quickly evolve new protection from parasites. This is because the sexually reproducing populations produce of offspring containing recombinant genes. During meiosis of the gametes the chromosomes undergo crossing over resulting in recombination. Due to recombination event, the sexually reproducing traits may evolve with quick protection from parasites. The infectious trait may be recessive and hence, it is at low rate. Over the period of time, the recessive trait may be lost and the resultant offspring may be healthy and rare population of snails increase in number as they are resistant and with low infection rate.Therefore, option C is correct.
2) The correct answer is option A.
A) The sexual population will stay rare or go extinct because the asexually reproducing snails can reproduce more quickly.
The rare snail strain with low infection rate reproduces asexually. When it is reproducing asexually means it passes the infectious trait to offspring. The infectious trait may be recessive and hence, it is at low rate. Over the period of time, the recessive trait may be lost and the resultant offspring may be healthy and rare population of snails increase in number or the trait may be expressed in all offspring and the rare snail population may go extinct.
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