What is the Law of Independent Assortment?
Principles
Law of dominance
Law of segregation
Law of independent assortment
Independent assortment definition from the words of Mendel is that they will not resemble their parental genes. Hence, allele 1 cannot influence allele 2 on any terms.
Reasons for Independent Assortment independently distributed to each other and to that of their parents:
Mendel's Experiment on the Law of Independent Assortment was set up with over 10,000 pea plants that he kept track of.
In the F1 progeny (first generation crossing), he obtained round-yellow seeds only.
The F2 progeny was labelled in the ratio of the phenotypic ratio and was inherited and scattered, individually.
The F2 progeny was labelled in the ratio of the phenotypic ratio of was inherited and scattered individually. In the F2 progeny (second generation crossing), the seeds were self-pollinated, i.e., pollination between the same flower or genetically same plants.
There were 4 unique results: Round-yellow (RRYY), round-green (RRyy), wrinkled-yellow (rryY) and wrinkled-green (rryy).
The F2 progeny was labelled in the ratio of 9:3:3:1; the phenotypic ratio was inherited and scattered individually.
To better understand his concept, have a look at the real-time law of independent assortment examples as follows:
Straight Red hair (RS)
Straight Brown hair (RB)
Curly Red hair (CR)
Curly Brown hair (CB)
Similarly, real-life examples can be found for various di-hybrid conditions including blood type, child's eye colour, the skin colour of cows, etc.
The law of independent assortment states that alleles of two or more genes are inherited independently within the gametes. Alleles received from one gene never influence the one received from the other gene. This is also called Mendel's laws of inheritance as it was founded by Gregor Johann Mendel. This law lays the foundation for the history of human genetics. According to this the combinations of traits of the progeny is never the same as the traits of the parents. The law is basically based on the fundamental principles of Law of dominance and Law of segregation
The principles, the law of dominance and law of segregation, was proposed by Mendel after his thorough experiment and observation on a monohybrid cross with pea plants. He designed the law after thorough and careful observation on the characteristics of the pea plants’ colour (yellow and green) and shape (round and wrinkled). Both in the parents and in the progenies. He found that a particular trait produced in the progeny does not resemble the traits of the parental genes.
Example of Law of Independent Assortment
Say a father has red hair (RR) with a straight hair type (SS) and the mother has brown hair (BB) with curls (CC). The son or daughter (progeny) of this couple (parent) can have the following genetic characteristic:
Straight Red hair (RS)
Straight Brown hair (RB)
Curly Red hair (CR)
Curly Brown hair (CB)
Similarly, real-life examples can be found for various di-hybrid conditions including blood type, child’s eye colour, the skin colour of cows, etc.
FAQs on Law of Independent Assortment
1. What are the reasons for Independent Assortment?
The reason behind the independent assortment is based on meiosis which is a type of cell division in which one cell divides twice to produce four cells and they are haploids since they contain half of the cellular genetic material as the original parents genetic material. In the human body, these haploid cells are actually the eggs in females and the sperms in males. According to Mendel’s law, the paternal and maternal genes divide independently creating unique cells. The characteristics of the progenies will be independent of that of their parents and are also independent of each other.
2. What was the experiment done by Mendel to develop the Law of Independent Assortment?
Mendel established the two fundamental principles from his experiment of performing a di-hybrid cross of two varieties of breeding pea plants of round-yellow seeds and wrinkled-green seeds. The resulting progenies are independent of each other in their genetic traits. The result of the cross-breeding was noted and listed by him as follows:
In the first generation progeny, the result was only round-yellow seeds.
In the second generation progeny, the seeds of the genetically same plants were pollinated. The results were Round-yellow (RRYY), round-green (RRyy), wrinkled-yellow (rrYY), and wrinkled-green (rryy).
Every parent, male or female, is homozygous (non-identical but similar alleles). The parental alleles are RR, YY, rr, yy, and their resulting gametes that support this principle of assortment are RY, Ry, rY, ry.
The second-generation progeny shows the ratio of 9:3:3:1; the phenotypic ratio of 3:1 was inherited and scattered individually.
Thus his experiment was a successful approach in giving a clear and quick understanding of the principles of independent assortment.
3. Does an Independent Assortment always occur?
Independent assortment usually occurs spontaneously in cases of reproduction when alleles of two or more genes assort independently into gametes. It occurs in the case of meiosis usually. In the human body, two independent gametes having half the DNA of the parent genes are used to form a diploid embryo or a zygote. The zygote inherits the DNA material from the parents. Independent assortment produces a new variation of traits by a new combination of the alleles. However, it has also been found that there are some allele combinations that may or may not inherit the traits independent of each other. Only genes located on separate non-homologous chromosomes sort independently.
4. What are the key takeaway points from this topic?
The key points of the law of independent assortment can be listed as follows:
Genes usually never influence each other when alleles are sorted into gametes.
Any combination of alleles for any gene is possible.
Any combination resulting from one or more genes is usually the product of the probability of the desired genotype at the first locus with the probability of the desired genotype at the other loci.
The probability method is used to find a particular genotype resulting from the cross while the fork line method is used to find all possible genotypes from a cross.
5. Explain the Law of Independent Assortment with an example.
It is quite easy to understand the Law of Independent Assortment with an example. Let us consider an example of birds with two visible traits as follows:
Feather colour (White and Blue)
Eye colour (Black and Red)
These two hybrid birds are crossed. For feather colour, the white feather is taken as (W) and is the dominant trait over blue colour (w). For eye colour, the dominant trait is Black (B) and the recessive trait is red (b). Birds with dominant traits Black eyes and white feathers will produce gametes during their maturity and during gamete production alleles of eye colour will not depend on alleles of feather colour. The offspring produced will have mixed traits.For example, one of the baby birds may have black eye colour (BB or Bb) and blue feather (ww). Other offspring may have BBWW, BbWW, BBWw, and BbWw.
6. What is the Basic Rule for the Laws of Inheritance?
According to Mendel, the 3 rules of inheritance include the principles of the law of dominance, the law of segregation, and the law of independent assortment.
7. When Does an Independent Assortment Usually Occur?
Independent assortment is common to sexual reproduction, where 2 gametes fuse to form a diploid embryo (zygote) that comes with the DNA material from the parents, necessary to form a new living species.
8. What will be the Result of an Independent Assortment?
The independent assortment resulting from the meiosis of a homologous pair will have an independent and unique set of characteristic combinations.
9. What is the Ratio for an Independent Assortment?
The phenotypic ratio of 9:3:3:1 will be the classic number for any independent assortment that happens between any di-hybrid genetic pairs.
10. What is Required for an Assortment to Occur Independently?
More than 2 alleles, either different or genetically similar are needed for getting unique chromosomes from the result of an independent assortment in the progeny.
