Question 1 (2 points) Questions 1 through 4 refer to the following problem: In c
ID: 214639 • Letter: Q
Question
Question 1 (2 points) Questions 1 through 4 refer to the following problem: In corn, the following recessive genes have been identified on chromosome 3: yg yellow-green seedlings wx waxy endosperm bz bronze color From a three-point testcross between plants heterozygous for all three genes and plants homozygous recessive for all three genes, the following data were obtained: yellow-green - 6 yellow-green, waxy 720 wild type 56 bronze, waxy 13 bronze -681 yellow-green, bronze -25 waxy - -31 yellow-green, bronze, waxy - 42 Which gene is in the middle? yg bz wxExplanation / Answer
Answer:
1). Middle gene = wx
2). Distance between genes yg and wx is 4.8 m.u.
3). Distance between genes wx and bz is 7.4 m.u.
Explanation:
Hint: Always recombinant genotypes are smaller than the non-recombinant genotypes.
Hence, the parental (non-recombinant) genotype is yg bz+ wx / yg+ bz wx+
1).
If single crossover occurs between yg& bz+
Normal combination: yg bz+ / yg+ bz
After crossover: yg bz / yg+ bz+
yg bz progeny= 25+42=67
yg+ bz+ progeny = 31+56=87
Total this progeny = 154
Total progeny = 1574
The recombination frequency between yg & bz+ = (number of recombinants/Total progeny) 100
RF = (154/1574)100 = 9.78%
2).
If single crossover occurs between bz+ & wx..
Normal combination: bz+ wx / bz wx+
After crossover: bz+ wx+ / bz wx
bz+ wx+ = 6+56 = 62
bz wx progeny = 13+42=55
Total this progeny = 117
The recombination frequency between bz+ &wx = (number of recombinants/Total progeny) 100
RF = (117/1574)100 = 7.43% = 7.4%
3).
If single crossover occurs between yg & wx..
Normal combination: yg wx / yg+ wx+
After crossover: yg wx+ / yg+ wx
yg wx+ = 6+25 = 31
yg+ wx progeny = 13+31=44
Total this progeny = 75
The recombination frequency between yg &wx = (number of recombinants/Total progeny) 100
RF = (75/1574)100 = 4.77% = 4.8%
Recombination frequency (%) = Distance between the genes (mu)
yg-------4.8mu------wx---------7.4mu---------bz
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