what is law of Independent assortment. please tell in easy words.
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Answer:
What is the law of independent assortment?
Mendel's law of independent assortment states that the alleles of two (or more) different genes get sorted into gametes independently of one another. In other words, the allele a gamete receives for one gene does not influence the allele received for another gene.
Example: Pea color and pea shape genes
Let's look at a concrete example of the law of independent assortment. Imagine that we cross two pure-breeding pea plants: one with yellow, round seeds (YYRR) and one with green, wrinkled seeds (yyrr). Because each parent is homozygous, the law of segregation tells us that the gametes made by the wrinkled, green plant all are ry, and the gametes made by the round, yellow plant are all RY. That gives us \text F_1F
1
start text, F, end text, start subscript, 1, end subscript offspring that are all RrYy.
The allele specifying yellow seed color is dominant to the allele specifying green seed color, and the allele specifying round shape is dominant to the allele specifying wrinkled shape, as shown by the capital and lower-case letters. This means that the \text F_1F
1
start text, F, end text, start subscript, 1, end subscript plants are all yellow and round. Because they are heterozygous for two genes, the \text F_1F
1
start text, F, end text, start subscript, 1, end subscript plants are called dihybrids (di- = two, -hybrid = heterozygous).
A cross between two dihybrids (or, equivalently, self-fertilization of a dihybrid) is known as a dihybrid cross. When Mendel did this cross and looked at the offspring, he found that there were four different categories of pea seeds: yellow and round, yellow and wrinkled, green and round, and green and wrinkled. These phenotypic categories (categories defined by observable traits) appeared in a ratio of approximately 9:3:3:19:3:3:19, colon, 3, colon, 3, colon, 1.
Illustration of the hypothesis that the seed color and seed shape genes assort independently.
In this diagram, the Y and R alleles of the yellow, round parent and the y and r alleles of the green, wrinkled parent are not inherited as units. Instead, the alleles of the two genes are inherited as independent units.
P generation: A yellow, round plant (YYRR) is crossed with a green, wrinkled plant (yyrr). Each parental generation can produce only one type of gamete, YR or yr.
F1 generation: The F1 dihybrid seeds are yellow and round, with a genotype of YyRr. The F1 plants can produce four different types of gametes: YR, Yr, yR, and yr. We can predict the genotypes of the F2 plants by placing these gametes along the top and side axes of a 4X4 Punnett square and filling in the boxes to represent fertilization events.
F2 generation: Completion of the Punnett square predicts four different phenotypic classes of offspring, yellow/round, yellow/wrinkled, green/round, and green/wrinkled, in a ratio of 9:3:3:1. This is the prediction of the model in which the seed shape and seed color genes assort independently.