how are traits inherited independently??
how are traits inherited independently??
Mendel established that it was possible to predict the outcome of breeding crosses involving a single pair of contrasted characteristics, he thought to study the inheritance of two pair of contrasted characters. Since two pairs of alleles are found in the heterozygotes, this condition is known as dihybrid inheritance. In one of his experiments Mendel used pea shape and pea cotyledon colour as the characteristics. In F1 generation the seeds were round and yellow. He know that these characters were dominant from earlier monohybrid breeding experiments but he was curious to know the outcome of the self pollinated F1 plants. He collected a total of 556 F2 seeds from the F1 generation which showed the following characteristics:
315 round and yellow,
101 wrinkled and yellow,
108 round and green,
32 wrinkled and green.
The proportions of each phenotype approximated to a ratio of 9:3:3:1. This is known as the dihybrid ratio. Mendel made two deductions from these observations.
1. Two new combinations of characteristics had appeared in the F2 generation: Wrinkled and yellow, and round and green.
2. The ratios of each pair of allelomorphic characteristics (phenotypes determined by different alleles) appeared in the monohybrid ratio of of 3:1 , that is 423 round to 133 wrinkled, and 416 yellow to 140 green.
On the basis of these results Mendel was able to state that the two pairs of characters (seed shape and colour), whilst combining in the F1 generation, seperate and behave independently from another in subsequent generations. This forms the basis of Mendel's second law or the principle of independent assortment which states that:
Any one of a pair of characteristics may combine with either one of another pair.
Mendel established that it was possible to predict the outcome of breeding crosses involving a single pair of contrasted characteristics, he thought to study the inheritance of two pair of contrasted characters. Since two pairs of alleles are found in the heterozygotes, this condition is known as dihybrid inheritance. In one of his experiments Mendel used pea shape and pea cotyledon colour as the characteristics. In F1 generation the seeds were round and yellow. He know that these characters were dominant from earlier monohybrid breeding experiments but he was curious to know the outcome of the self pollinated F1 plants. He collected a total of 556 F2 seeds from the F1 generation which showed the following characteristics:
315 round and yellow,
101 wrinkled and yellow,
108 round and green,
32 wrinkled and green.
The proportions of each phenotype approximated to a ratio of 9:3:3:1. This is known as the dihybrid ratio. Mendel made two deductions from these observations.
1. Two new combinations of characteristics had appeared in the F2 generation: Wrinkled and yellow, and round and green.
2. The ratios of each pair of allelomorphic characteristics (phenotypes determined by different alleles) appeared in the monohybrid ratio of of 3:1 , that is 423 round to 133 wrinkled, and 416 yellow to 140 green.
On the basis of these results Mendel was able to state that the two pairs of characters (seed shape and colour), whilst combining in the F1 generation, seperate and behave independently from another in subsequent generations. This forms the basis of Mendel's second law or the principle of independent assortment which states that:
Any one of a pair of characteristics may combine with either one of another pair.
