Question

what is dihybrid cross? explain with a suitable example by checker board method​

Answer 1

Answer:

dihybrid cross is a cross between two individuals that are both heterozygous for two different traits. An example, let's look at pea plants and say the two different traits we're examining are color and height.

Explanation:

Gametes yr yr

YR YyRr YyRr

YR YyRr YyRr

To find out whether one pair of alleles affects or influences the inheritance pattern of other alleles. In a dihybrid cross, Mendel considered two traits simultaneously. A cross conducted between two pure parents differing in two pairs of contrasting characters. He studied round and wrinkled seeds characters along with yellow and green colors.

Yellow and round are dominant alleles so in an F1 generation all plants with yellow and round are used. Above table is punnet square for the F1 generation.

Mendel allowed self-pollination in each hybrid of F1 and collected seeds separately and obtained F2 generation. checkerboard or punnet square for F2 generation is shown in the image. He found seeds of four types in 9:3:3:1 ratio which is dihybrid ratio.

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Answer 2

Answer: Dihybrid cross is the cross in which 2 characters are involved and their pattern of inheritance is recorded simultaneously . It is also called 2- factor cross.

Lets take an example of 2 types of true- breeding pea plants that were different in regarding to their 2 characters.

1st plant had round & yellow seeds- RRYY

2nd plant had wrinkled & green seeds - rryy  

Explanation:

• F1 generation- cross the                                    

        true breeding plants to each other     RRYY             X              rryy                                                                                              

                                                                            ↓                                    ↓                                                                                     

• Gametes                                                   RY                                  ry

                                                                                               ↓

• Collection of many seeds and                                 RrYy

       phenotype is recorded                                                 ↓

• F1 seeds are planted and grown and then  RrYy    X     RrYy

       further are allowed to self- fertilized or                                                          Self- crossed producing the seeds of F2 generation

Checker board or Punnett square showing F2 generation is attached below

Results:-

• F1 generation- All round & yellow seeds

• F2 generation- 315-round & yellow seeds

                                  108- round & green seeds

                                  101- wrinkled & yellow seeds

                                   32- wrinkled & green seeds

If we divide each of these numbers by 32 (the no. of pants with wrinkled & green seeds)

• The phenotypic ratio of F2 generation will be- 9.8: 3.2: 3.4: 1.0, if we count the experimental error then approximated ratio will be- 9:3:3:1 (In total 16 combinations are possible by randomly combining male and female gametes).

                                               9- Round & Yellow seeds

                                               3- Round & Green seeds

                                               3- Wrinkled & yellow seeds

                                               1-   Wrinkled & green seeds