Plump kernels S is dominant over shrunken s Colored kernels

Plump kernels (S) is dominant over shrunken (s) Colored kernels (C) is dominant over colorless (c) Starchy kernels (W) is dominant over waxy (w). A trihybrid (Cc Ss Ww) plant is testcrossed and the following progeny are obtained: 2708 plump, colorless, waxy 2538 shrunken, colored, starchy 626 plump, colorless, starchy 601 shrunken, colored, waxy 116 shrunken, colorless, starchy 113 plump, colored, waxy 4 plump, colored, starchy 2 shrunken, colorless, waxy Indicate the genotype and phenotype of the tester parent Determine the gene order, write out a map. i Calculate genetic distances between the genes, indicate it on your linkage map. Write out the genotype of the trihybrid plant used in a testcross such that your notation illustrates whether the mutant alleles are in cis or trans. (Tip: Make sure to use the correct gene order!) Write out the genotypes and phenotypes of the parents of the trihybrid plant Each parent came from a separate true-breeding stock.

Solution

Answer:

6.1).

Tester plant = shrunken, colorless, waxy(ssccww)

6.2).

C---3.5 m.u.--s---------18.33m.u.----------W

CsW/cSw

6.3).

Phenotype

Shorthand

Number of progeny

Plump, colorless, waxy

Scw

2708

Shrunken, colored, starchy

sCW

2538

Plump, colorless, starcy

ScW

626

Shrunken, colored, waxy

sCw

601

Shrunken, cololess, starchy

scW

116

Plump, colored, waxy

SCw          

113

Plump, colored, starchy

SCW

4

Shrunken, cololess, waxy

scw

2

Imagine the order of genes is Scw/sCW

1.     If single cross over (SCO) occurs between S&c

Normal order= S---------c & s-----C

After cross over= S-----C & s------c

S-----C recombinants are 113+4= 117

s------c recombinants are 116+2 = 118

Total recombinants = 235

RF = (235/6708)*100 =3.5%

2.     If single cross over (SCO) occurs between c & w

Normal order= C---------W & c----w

After cross over= C-----w & c------W

C-----w recombinants are 601 + 113 = 714

c------W recombinants are 626+116=742

Total recombinants = 1456

RF = (1456/6708)*100 = 21.7%

3.     If single cross over (SCO) occurs between S & w

Normal order= S---------w & s------W

After cross over= S-----W & s------w

S-----W recombinants are 626+4=630

s------w recombinants are 601+2=603

Total recombinants = 1233

RF = (1233/6708)*100 =18.33%

% RF = Map unit distance

The order of genes is -----

C------3.5 m.u.------s------18.33m.u.-------W

6.4).

Genotype of trihybrid plant= CsW/cSw

The mutant alleles ae in trans configuration

6.5).

Genotypes of trihybrid parent plants are

CCssWW and ccSSww

Phenotype	Shorthand	Number of progeny
Plump, colorless, waxy	Scw	2708
Shrunken, colored, starchy	sCW	2538
Plump, colorless, starcy	ScW	626
Shrunken, colored, waxy	sCw	601
Shrunken, cololess, starchy	scW	116
Plump, colored, waxy	SCw	113
Plump, colored, starchy	SCW	4
Shrunken, cololess, waxy	scw	2