Question

Explain dihybrid cross with suitable example.

Answer 1

Hint: Di Means Two and hybrid means genetically mixture of two offspring.
Dihybrid cross in which a breeding experiment dealing with two pairs of contrasting traits.

Complete Answer:
- Mendel took two pairs of pea plants which are seed shaped - round, wrinkle and seed coat yellow and green.
- In this experiment the round shape of seed and yellow seed coat Color is dominant over wrinkled seed shape and green color of seed.
- Round shape of seed is regulated by R gene and its recessive form is regulated by R gene. Yellow color of a seed coat is regulated by Y gene and its recessive form green color of seed coat is regulated by Y gene.
- Mendel took an experiment between the round shape of seed and seed coat color simultaneously.
- Round shape of seed and yellow color seed coat genotype is RRYY and wrinkle shape of seed and green color seed coat genotype is rryy. In gametes alleles RY and ry are present and cross for production of F1 generation when the seeds from F1 generation are produced Mendel found all the plants seeds have round shape and yellow seed coat color.

- When F1 generation plants are self pollinated for production of F2 generation Mendel found in F2 generation four kind of trait are present two are parental and two are new these are round shape of seed and yellow color of seed coat, wrinkle shape of seed and green color of seed coat, round seed and green color of seed coat, wrinkle shape of seed and yellow color of seed coat.

Phenotype ratio is 9:3:3:1
Genotype ratio is 1:2:1:2:4:2:1:2:1

Note: In dihybrid cross we see two trait are parent and two trait are in new combination like round shape seed and yellow seed coat color , wrinkle shape seed and green seed coat color (parent trait) new combination like wrinkle shape seed and yellow seed coat color, round shape seed and green seed coat color (new combination).
Means to say movement of alleles are independent from each other there is no effect of movement of one gene to another.