3) You have examined the results of the following crosses using pure-breeding fr
ID: 17543 • Letter: 3
Question
3) You have examined the results of the following crosses using pure-breeding fruit flies.i) Gray-bodied males × ebony-bodied females yield all gray-bodied flies. The same is true if gray-bodied
females are crossed with ebony-bodied males.
ii) Long-bristled males × short-bristled females yield all long-bristled flies. The same is true if long-bristled
females are crossed with short-bristled males.
iii) Ebony-bodied, short-bristled males × gray-bodied, long-bristled females yield all gray-bodied, long
bristled flies.
a) (10 Points) What information concerning body color and bristle length is provided by crosses (i) and (ii)?
b) (10 Points) Write the genotype for the parents in cross (iii) and the expected genotype of the F1 from.
c) (10 Points) An F1 female from cross (iii) was back-crossed to his ebony-bodied, short-bristled father. Assuming
independent assortment, write the expected genotype(s) and the proportion of each genotype for the progeny of this
cross.
d) (10 Points) An F1 female and F1 male from cross (iii) were mated to produce an F2. Assuming independent
assortment, what is the probability that a gray-bodied, long-bristled progeny from that cross will be a dihybrid?
Explanation / Answer
(a) The information revealed by (i) and (ii) is: 1.Ebony color genes are recessive. 2.Short bristled feather genes are recessive. (b) Suppose: Gray = G, Ebony = g, Long bristled = L, Short bristled = l. So, Parents: Male = ggll Female = GGLL Gametes = gl GL F1 = gGlL (c) Male = ggll Female = gGlL Gametes = gl gl, GL, gL, Gl F1 = ggll, gGlL, ggLl, gGll Gray, short : Ebony Short : Gray Long : Ebony Long = 1:1:1:1 (d) F1 Parents: Male = GgLl Female = GgLl Gametes: GL, gL, Gl, gl X GL, gL, Gl, gl F2: GGLL GgLL GGLl GgLl gGLL ggLL gGlL ggLl GGlL GgLl GGll Ggll gGlL gglL gGll ggll So, combinations for gray, long are: GGLL = 1 GgLl = 4 GgLL = 2 GGLl = 2 Total = 9 Dihybrids are : GgLl = 4 So, probability = 4/9.
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.