Mendel’s Law Of Inheritance

First, we discuss what inheritance is. Thus, inheritance is how children receive genetic information from their parents. Because of this inheritance, children have similar characteristics to their parents. Mendel, a 19th-century monk, gave this law of inheritance. He was dealing with a hybridization experiment in a garden pea plant (its scientific name is Pisum sativum). And cultivated 28,000 pea plants in seven years. And by observing it, he gives us the law of inheritance. This law is proposed in three main laws: the law of segregation, the law of dominance, and the law of independent assortment. Here we discuss all of these in detail. 

Mendel’s Experiment On The Pea Plant 

Medal has selected the pea plant for the experiment due to some reason:-

• He uses a pea plant because it can easily grow and be maintained. 

• It has a very contrasting and distinct character. 

• It is an annual plant. So, we can easily observe many generations of pea plants in a short period. 

• Pea plants can be self-pollinated and cross-pollinated. 

Mendel has conducted the Monohybrid Cross Experiment and Dihybrid Cross Experiment to learn the law of inheritance and the law of segregation. He takes seven contrasting traits in the Pea plants to get the laws of Mendel. 

Monohybrid Cross

Medal had taken two pea plants of opposite traits. The first one is short and the other tall. And he crossed them. He observed all tall plants in F1 progeny. Next, he took F1 progeny and found three tall plants and one short plant. According to this observation, Mendel has given the law of segregation and the law of dominance. 

Dihybrid Cross

In the next experiment, Mendel takes two traits with two alleles. The first is a round-yellow seed, and the other is a wrinkled-green seed. And crossed them. He observed all ’round-yellow seeds’ in F1 progeny. It shows that round-yellow is the dominant character. Next, he self-pollinated the F1 progeny. Then, he received four different traits. 

First- Round-yellow – 9

Second- round green – 3

Third- wrinkled yellow – 3

Last – wrinkled-green – 1 

So, the ratio of 9:3:3:1.

This cross will give laws of Independent assortment. 

Law Of Dominance 

It is one of the important laws of Mendel. The law of dominance says the offspring will inherit the dominance character in the phenotype. Some alleles show the dominant characters, while others show suppressed recessive characters. 

Law Of Segregation 

When two traits cross in one hybrid pair, they will not mix in this law. They segregate in gamete formation and combine in fertilization. So, the offspring will have one factor from each parent. 

The law of segregation gives a phenotypic ratio of 3:1.

Here, homozygous dominant and heterozygous offspring are dominant. On the other hand, the homozygous-recessive are recessive traits. 

Law Of Independence Association

In the law of independent association, the two genes separate independently from each other and other traits. So, we found separate genes for separate traits and characters. Therefore, the genes will independently pass from the parents to the offspring. We get a 9:3:3:1 ratio in this law. 

Forked-Line Method

In this method, we analyze the trihybrid cross. So, we cross between F1 heterozygotes, which we get from a cross between AABBCC and aabbcc parents. First, we create rows equal to the number of genes and segregate alleles on the forked lines. So, we multiply the values with each forked path to get the F2 offspring. Therefore, we get the F2 phenotypic ratio is 27:9:9:9:3:3:3:1 in a trihybrid cross. 

Important Key Points

You need to know the following key points to understand the laws of Mendel. 

• Allele:- When the genes transfer from parent to child in a pair, this is called an allele. 

• Genotype:- The genetic material or genetic makeup of an organism is called genotype. 

• Phenotype:- The physical appearance which has observable characteristics is called the phenotype. 

• Homozygous:- The same alleles are homozygous. 

• Heterozygous:- The different alleles are heterozygous. 

• Dominant:- The character expressed in offspring is called dominant character. 

• Recessive:- The character suppressed in offspring is called recessive character. 

Conclusion

We know that Mendel gives his law by observing pea plants for seven years. Mendel’s law of inheritance gives us three important laws: the law of dominance, the law of segregation, and the law of independent assortment. Moreover, The main purpose of this experiment is to know whether the traits would be dominant or recessive. And the traits would affect each other or be inherited. Also, we know that DNA can transform traits from the laws of Mendel. Therefore, we know the purpose and laws of Mendel. We will further know some genetic linkage and violations of the law of Independent Assortment and many more things.