Question

In soybeans, dwarf (D) is dominant to tall (d), round (R) is dominant to oval (r), and green (G) is dominant to brown (g). The genes are linked and the map is given below. Pure-breeding tall, round, green plants were mated to pure-breeding dwarf, oval, brown plants. The F1 were testcrossed. All loci are autosomal. The coefficient of coincidence is 1.

Height

Shape

Color

14cM

22cM

Rank the progeny phenotypes below to indicate their frequency in the testcross progeny based on the data above. Use 1 to indicate the most frequent then 2, then 3 and let 4 indicate the least frequent.

tall, oval, green
tall, oval, brown
tall, round, brown
tall, round, green

Answer 1

Answer:

Tall, oval, green----4 = 1.5%

Tall, oval, brown---3 = 5.5%

Tall, round, brown—2 = 9.5%

Tall, round, green---1 = 33.5%

Explanation:

dRG/dRG x DrG/Drg –Parents

dRG/Drg---------------F1

dRG/Drg x drg/drg ---Testcross

Explanation:

d---14cM---r----22cM--g

Distance between the genes (mu) = (%) of recombination frequency

Expected double crossover frequency = 22% x 14% = 0.0308

Coefficient of coincidence = obsereved dco / expected dco

1 =?/0.0308

Observed dco = 1 * 0.0308 = 0.0308 = 3%

Explanation:

Class of gametes	Phenotype	Frequency of reciprocal pair	Numbers	Frequency of each class	Phenotypes
Parental	Drg	1- all recombinant progeny	100%-(19%+11%+3%) = 67%	33.5%	Dwarf, oval, brown
	dRG			33.5%	Tall, round, green
SCO 1	DRG	RF in region 1 = SCO1 - DCO	SCO1 = 14%-3% = 11%	5.5%	Dwarf, round, green
	Drg			5.5%	Tall, oval, brown
SCO 2	DrG	RF in region 2 = SCO2 - DCO	SCO2 = 22% – 3% = 19%	9.5%	Dwarf, oval, green
	dRg			9.5%	Tall, round, brown
DCO	DRg	(RF in region 1) * (RF in region 2)	3%	1.5%	Dwarf, round, brown
	DrG			1.5%	Tall, oval, green