• December 28, 2021

What are Mendel’s law of inheritance and what are some examples?

What are Mendel’s law of inheritance and what are some examples?

Mendel’s laws of inheritance

Inheritance can be described as the process of receiving information by a child from his parent. The entire process of heredity is based on inheritance and that is why, the offspring look like their parents. In simple language, the members of the same family have similar characteristics.

During the mid-19th century, people gradually began to understand about inheritance. This understanding of inheritance was made known to people by a scientist named Gregor Mendel. He developed certain laws to know about inheritance, called as Mendel’s laws of inheritance.

Mendel conducted experiments on inheritance with the help of common pea plant by taking 7 features of the plant. They are:

  • Stem height
  • Pod shape
  • Pod color
  • Flower position
  • Flower color
  • Seed color
  • Seed shape.

Why did Mendel select pea plant for his experiments?

Mendel selected pea plant for his experiments due to the following reasons:

  • The pea plants can be maintained and grown easily.
  • Pea plants are self-pollinating and can also be cross-pollinated.
  • Pea plants are annual plants. Thus, many generations can be known within a limited period of time.
  • It has many contrasting characters.

Mendel performed two important experiments to state the laws of inheritance. The two experiments were:

  1. Monohybrid cross experiment
  2. Dihybrid cross experiment

While conducting the experiments, Mendel discovered that some factors always got transferred down to the offspring in a steady manner. Those factors are called genes i.e., genes are said to be the units of inheritance.

Monohybrid cross

Here, in this experiment, Mendel took two pea plants having opposite traits (one shot and one tall) and both of them were crossed. He discovered that the first-generation offspring were found to be tall and named it as F1 progeny. After that, he crossed F1 progeny and got both tall and short progeny in the ratio 3:1.

Mendel even carried this experiment with other contrasting traits such as green peas vs yellow peas, round vs wrinkled, etc. Inall the experiments, he discovered that the results were the same. From this, he propagated the laws of segregation and dominance.

Dihybrid cross

In this experiment, Mendel took two traits each having two alleles. He crossed wrinkled-green seed and round-yellow seeds and discovered that all the first-generation progeny (F1 progeny) were round-yellow. This can be said that dominant traits were round in shape and yellow in color.

After this, Mendel self-pollinated the F1 progeny and got 4 different traits. They were wrinkled-yellow, round-yellow, wrinkled-green seeds and round-green in the ratio 9:3:3:1.

Mendel conducted experiments for other traits and found that the results were similar. From this, Mendel propagated the law of independent assortment.

Mendel carried out these experiments by breeding two different features- tall vs short height till they became pure breeding. He performed breeding experiments with all the features and jotted down the observations of inheritance and came to these conclusions:

  • One feature, for example, yellow pods will always hide the other form eg: green pods in the F1 or the first generation of the cross. The feature which was visible was known as the dominant trait and the hidden feature was known as the recessive trait.
  • The plants were let to self-fertilize in the second generation. This made the recessive trait again appear in a small portion of plant. Every three plants possessed the dominant trait and one plant possessed the recessive trait.
  • The conclusion made by Mendel was that the features in plants were inherited independently and no individual feature impacted on other traits.

The law of dominance

According to this law, parents having pure contrasting traits are crossed together, then only the dominant trait will show as the phenotype on the next generation. The recessive trait will be hidden.

The law of segregation

According to this law, only a single copy of two gene copies which are there in a cell, is supplied in each gamete (sperm or egg cell) that it produces and the allocation of these gene copies is not steady. According to this law, the offspring will inherit one gene copy from each parent. This law is also called as Mendel’s second law of inheritance.

Do you know the answer of the below question?

Q.A genotype AaBBCcDd can produce how many types of gametes?

The key points of this law are:

  • A gene occurs in multiple forms of an allele.
  • In meiosis, the allelic pair of a cell splits and each gamete contains a single allele.
  • Every living organism possess two alleles for each trait- dominant and recessive.

The law of independent assortment

According to this law, when gametes form, a pair of trait separates independently of another pair. Since the individual heredity factors arrange independently, different traits have equal opportunity to appear together.

What are phenotypes and genotypes?

Phenotype: A phenotype is an observable characteristic of an organism. It is due to the interaction of its genotype and environment.

Some examples re skin and hair color.

Genotype: The genetic makeup of a cell which are responsible for its characteristics is known as the genotype of a cell.

Some examples are the pea plant’s tall dominant genes.

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