QUESTION 16 2 points Save Answer Fine spines (s), smooth fruit (tu), and uniform

Question

QUESTION 16 2 points Save Answer Fine spines (s), smooth fruit (tu), and uniform fruit color (u) are three recessive traits in cucumbers. The genes responsible for these three traits are linked on the same chromosome. A plant heterozygous for the recessive and dominant alleles at all three genes is used in a testcross and the following progeny are produced. 70 S u Tu 13 tu tu 92 tu s U Tu 21 S u tu 21 230 TOTAL What is the genetic map distance between the Uand Tu genes? The calculator function on your workstation is available.) O A. 2.6 map units o B. 13.0 map units O C. 15.7 map units O D. 18.3 map units O E-20.9 map units

Explanation / Answer

Answer: D. 20.9 map units

Explanation:

Parental combinations are more so, the parental combinations are s u Tu & S U tu

1. If single cross over (SCO) occurs between s & u and S & U

Normal order= s -------- u & S ----- U

After cross over= s ----- U & S ------ u

s ----- U recombinants are 17+21= 38

S ------ u recombinants are 13+21= 34

Total recombinants = 72

RF = (72/230)*100 =31.30%

2. If single cross over (SCO) occurs between u & Tu and U & tu

Normal order= u --------- Tu & U --------- tu

After cross over= u --------- tu & U ------ Tu

u --------- tu recombinants are 4+21=25

U ------ Tu recombinants are 2+21=23

Total recombinants = 48

RF = (48/230)*100 = 20.87%

3. If single cross over (SCO) occurs between s & Tu and S & tu

Normal order= s --------- Tu & S------tu

After cross over= s --------- tu & S --------- Tu

s --------- tu recombinants are 4+17= 21

S --------- Tu recombinants are 2+13=15

Total recombinants = 36

RF = (36/230)*100 = 15.65%

% RF = Map unit distance

The order of gene is -----

S----15.65 m.u.-----Tu-------20.87 m.u.------U

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