Background: You are a herpetologist studying the pacific coast tree frog, Hyla r
ID: 11025 • Letter: B
Question
Background: You are a herpetologist studying the pacific coast tree frog, Hyla regilla. These frogs are typically green. However, a rare blue variant was recently discovered in Eureka (previously on display at the HSU Natural History Museum: http://now.humboldt.edu/news/rare-blue-frog-struts-its-stuff-at-nhm/). You have been studying these frogs for many years and have a true breeding “green strain” in captivity.You know that color is determined by special pigmented cells in the skin of the frog. “Green” results from production of blue or grey pigmentation and yellow pigment (blue plus yellow makes green). The blue-grey pigment is produced in the iridophore cells. The blue pigmentation filtered by yellow pigment production in the xanthophore cells to generate an overall green color. Hypoxanthism is a condition in which the yellow pigmentation is greatly reduced in the xanthophores. You suspect this to be the case in the blue frog discovered in Eureka.
A genetic screen in zebrafish identified 17 genes with mutations that disrupt expression yellow pigment. Some of these genes affect pigment production (the biosynthetic pathway for yellow pigment is non-functional), others affect the development of the xanthophore cells (no cells are produced so no yellow pigment can be made).
You decide to use this information and the molecular tools you learned of in BIOL340 genetics to identify the molecular basis of the blue color in this frog……
Q: You decide to test if the blue phenotype is dominant or recessive to green. Design an experiment that will enable you to test this and describe the expected results from this experiment if the blue trait is “dominant” and if it is “recessive”. (Remember you have a true breeding green strain).
Explanation / Answer
True breeding: Breeds same trait with identical true breeding organism. Iridophore cells produce blue pigment. Yellow produced on top of blue and appears green. Xanthophore cells produce yellow. Hypozanthism= less yellow to appear blue 17 genes Xanthophore cells grow -> Produce yellow pigment -> Yellow over blue produce green A B C No A results in no B and therefore no C A but no B results in no C --- True Breeding Green: 1)GG or 2) gg Blue Frog: 1)bG or bb or 2) Bg or BB 1) If green is dominant, filial generation 1 will be green either Gb or GG depending on what the blue frog is which is unknown and has not been verified to be true breeding. 2) The first off spring will be green or blue.
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