Question

Pea plants with double hybrid yellow round seeds (YyRr) are crossed with plants having single green round seeds (yyRr). The progeny shall be?
(a)2:2:1:1
(b)1:1:1:1
(c)9:3:3:1
(d)3:1:3:1

Answer 1

Hint: Dihybrid cross is a cross when at a time two traits and their alternative forms are considered during hybridization experiment. Steps of Experiment are the same as that of a monohybrid cross, but two characters and their alternative forms are considered simultaneously.

Complete answer:
Punnett square -This a diagram that is used to predict an outcome of a particular cross or breeding experiment by giving information of its phenotypic and genotypic ratio.

Additional Information:
-Figure out the alleles:
Identify what trait/letter is Dominant (Y – yellow colour seed)
Identify what trait/letter is Recessive (R – Round seed)
-Draw your box (16 squares for dihybrids!)
-Determine the Possible gametes (sex cells) that could be made from the two parents.
You should have 4 combinations (For RrYyand Rryy-Ry, Ry, ry and ry: RY, Ry, rY and Ry )
-Put the same letters together again
Make sure to put dominant alleles First!
-Determine your possible Genotypes!
Ensure that all the possible genotypes should add up to 16!
-Determine your possible Phenotypes!
Ensure that all the possible phenotypes should add up to 16!

Phenotypic Ratio obtained- Round Yellow: Wrinkled Yellow: Round Green: Wrinkled Green
6 : 2 : 6 : 2
On the basis of results of Dihybrid cross, Mendel proposed his second law of inheritance and is called as law of Independent Assortment of factors This law states that in a hybrid union for two or many traits, the different traits are inherited independently of each other as genes for two characteristics are inherited independently.
In his studies, each character was governed by a single gene and its two alleles and the genes responsible for those characters were probably present on different chromosomes and were not linked. Even if the genes were present on the same chromosome they were present at a distance sufficient for crossing over exception are linked genes.
So, the correct answer is, ‘3:1:3:1.’

Note: -Monohybrid crosses for all the seven traits independently and he was able to differentiate between dominant and recessive form for each trait.
-Mendel was then interested to know whether inheritance of two characters are influenced by each other or are inherited independently.