The toxins are incredibly variable. A single snail can deliver >100 peptide toxins. Some toxins attack peripheral nerves, others affect the central nervous system, and some paralyze muscles. A study of the genes underlying these peptides shows that many have arisen through duplication and divergence. The graph below shows the dN and dS values for different parts of the toxin. Proportion of substitutions Prepro Toxin ds (changes at silent sites) dN (changes affecting amino acid) Codon window 1 to 14 8 to 21 15 to 28 22 to 35 29 to 42 36 to 49 43 to 56 50 to 63 What is the (single) best explanation for the high dN in the toxin region but not in the preprotein region that is removed from the mature toxin? - The mutation rate is higher in the toxin region. - The terminal ends of genes typically evolve faster. - The snail toxin is likely undergoing "arms race" coevolution with the fish, and only the toxin part would be affected. - The peptide sequence within the toxin region is free to vary as it does not affect fitness or ability of the snail to consume its prey. - Gene duplication is usually followed by nonfunctionalization and faster divergence of sequences.
Added by Brian J.
Close
Step 1
The mutation rate being higher in the toxin region could be a possible explanation, but it doesn't explain why the preprotein region doesn't have a high dN value. Show more…
Show all steps
Your feedback will help us improve your experience
Madhur L and 85 other Biology educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
A species of marine snail is found in shallow waters near coastlines. This snail feeds on detritus on the ocean bottom. Researchers noticed that snails in one area had a mottled appearance, while snails in another area were solid in color. The researchers set up areas in each region for study and then released both mottled and solid snails into the solid snail region and released both mottled and solid snails into the mottled snail region. The survival rate of each variant was measured. Results are summarized in this table. Construct a possible hypothesis that accounts for these data. Explain your reasoning. a. A possible hypothesis is that the coloration of the snail is dependent on environmental conditions. Camouflage in both mottled and solid snails is best during optimum environmental conditions and does not change according to the region in which they are placed. b. A possible hypothesis is that the coloration of the snail is an adaptation in the form of camouflage to protect the snail from predators in the region it is invading. Mottled snails are best camouflaged in the solid snail region and stand out to predators and suffer greater predation when placed in their native region. c. A possible hypothesis is that the coloration of the snail is an adaptation in the form of camouflage to protect the snail from predators in its native region. Mottled snails are best camouflaged in their native region and stand out to predators and suffer greater predation when placed in the region normally occupied by solid snails. d. A possible hypothesis is that the coloration of the snail is an adaptation in the form of camouflage to protect the snail from predators in its native region. Solid snails are best camouflaged in mottled snail region and are more obvious to predators when placed in their native region.
Caroline J.
Recommended Textbooks
Biology for AP Courses
Objective Biology for NEET
Introduction to General, Organic and Biochemistry
Transcript
Watch the video solution with this free unlock.
EMAIL
PASSWORD