If in a test cross, equal number of round yellow seeded plants and wrinkled yellow seeded plants are obtained, what is the genotype of the plant ?

(1) RRYY (2) RrYY (3) RrYy (4) RRYy  

 

Asked by Atulcaald | 19th May, 2018, 01:37: AM

Expert Answer:

In a dihybrid test cross, a plant which produces round and yellow seeds has four possible genotypes- RRYY, RrYY, RRYy and RrYy. To determine the genotype of such a plant, it must be crossed with the one producing wrinkled and green seeds. Such a plant has only one possible genotype, rryy and produces only one type of gamete, namely ry. From the table, it can be seen that the unknown genotypes can be identified from the results of the test cross.

Possible genotypes of plants producing round, yellow seeds

Possible gametes

Genotypes of offspring crossed with the plant producing wrinkled green seeds (ry)

Phenotype (type of seeds produced)

RRYY

RY

RrYy

All round and yellow

RrYY

RY

RrYy

½ round, yellow

rY

rrYy

½ wrinkled, yellow

RRYy

RY

RrYy

½ round, yellow

Ry

Rryy

½ round, green

RrYy

RY

RrYy

¼ round, yellow

Ry

Rryy

¼ round, green

rY

rrYy

¼ wrinkled, yellow

ry

rryy

¼ wrinkled, green

From the above table, it is clear that if equal number of round yellow seeded plants and wrinkled yellow seeded plants are obtained, then the genotype of the parent plant has to be RrYY.

Answered by Sheetal Kolte | 21st May, 2018, 10:17: AM

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