Heredity

What is Heredity?

Heredity refers to the transfer of genetic traits from parents to their offspring; in sexual reproduction, both parents’ DNA come together and combine to provide offspring with two types of genes for each character. Later, each dominant gene carries a single character, which is visible in offspring.

Hereditary in Asexual reproduction

In asexual reproduction, one parent is involved, which results in organisms producing their exact copies. As a result, offspring are physically and genetically similar to their parents. This way, genetic uniformity can be seen in these organisms. With asexual reproduction, a population with genetic similarities can be produced from a single organism. 

A Gene is the hereditary vehicle of genetics, helping transfer a set of genes from parents to children. Genes can be found on DNA, and their function is to synthesize protein or RNA. Gene is of two types dominant and recessive. Character from a dominant gene is more expressed in the offspring, while the character carried by a recessive gene remains dormant.  

Genetics 

The study of genes and heredity is a science that comes under the umbrella of genetics. (Genetics is a Greek word meaning “to generate”) this term was given by William Bateson, a British biologist, in 1905.

Gregor Johann Mendel and his work 

Gregor Johann Mendel, the father of genetics, is famous for his experiment exhibiting inheritance patterns. He is the one who gave the concept of inheritance, the transfer of traits from one generation to another is explained by him with his experiment. After his experiment, he gave the unit of inheritance, which he named factors, later renamed genes.

He conducted his research in his garden and studied the inheritance pattern in Pisum Sativum, commonly known as a pea. He studied seven different traits, like the color of pods, the shape of pea seeds, the height of plants, etc.  Mendel conducted this experiment for seven long years.  

Mendel conducted two main experiments -

• Monohybrid cross

• Dihybrid cross

Contribution of Mendel

Mendel’s contribution in giving the bases for the study of inheritance and genetics is remarkable. For example, he is the one who deducted that factor(gene) is found in pairs.

It is because of his experiments that people have an understanding of inheritance. Inheritance is the reason behind the genetic similarity of an individual with his family.

Inheritance provides characteristics that distinguish an individual from their parents.

He also provides the bases for the law of segregation of genes which are later expressed in an individual if they have a dominating gene. 

He also conducted a hybridization experiment on the pea plant.

Mendel concluded and compiled his work into four postulates that later became the bases for the study of inheritance. Mendel’s law of inheritance −

• Principle of Paired Factors − At first, Mendel thought the unit of hereditary factors(genes) existed in pairs, and it was only later, that he came up with a theory on separating paired factors during gamete formation. However, he later concluded that every pair of factors(genes) would assort independently into the newly formed gametes.

• Dominance − Characters are controlled by a unit of heredity known as factors, genes, or alleles found in pairs. In a hybrid, only one allele of two can express itself, which is the dominant allele. Due to hybrid, one allele that would not be able to express itself is called receive allele. 

• Law of Segregation − Two alleles carrying different characters can remain present in an individual. Although during gamete formation in meiosis, pairs of alleles get separated, and only one allele remains for each character. That allele will be passed down to the offspring. 

  The Law of segregation is also known as the law of purity of gametes.

• Law of Independent Assortment − According to Mendel, in independent assortment, while the inheritance of two or more characters, an individual character gets assorted independently during gamete formation. Hence each gamete contains only one allele independently segregated from the pair of alleles present. So now, each gamete carries each only one allele of each character. Because of variable assortment, each distinct feature has an equal chance to express. Independent assortment state that the inherited gene or characters are independent of another inherited pair of genes.

FAQs

Qns 1. What is Heredity?

Ans −The transmission and transfer of genetic characters from a parent’s generation to successive generations.

Qns 2. What is Inheritance? 

Ans −This is a process of transferring genetic information from parents to their children. Inheritance is the reason why children look like their parents

Qns 3. What are Mendel’s four principles of heredity?

Ans −George Mendel gave four principles of heredity −

• Principle of paired factors

• Law of Dominance

• Law of Segregation

• Law of Independent Assortment

Qns 4. Why did Mendel choose pea plants for his experiments?

Ans −There were the following reasons why Mendel chose the pea plant −

• The Pea plants can be self-pollinating, making them compatible with self and cross-pollination.

• Pea plant followers are bisexual and carry both male and female gametes.

• It is easy to identify and differentiate between different physical characteristics.

• The short lifecycle of the pea plants provides grounds to study later generations.

• The Pea plant is also a low-maintenance plant.

Qns 5. What are Mandel's different contrast charters for his experiment in pea plants?

Ans −Following are the seven traits that Mendel studied during his pea garden experiment −

• Shape of pea − round and wrinkled

• The shape of a pod of pea − constricted or inflated.

• Size of pea plant − tall or dwarf.

• Position of flower − terminal or axial.

• Colour of pea − green or yellow.

• Color of pea pod − green or yellow.

• Colour of flower − purple or white.

Qns 6. What was the contribution by Gregor Mendel in genetics?

Ans −

• He came up with the concept of factors later known as genes.

• He gave the concept of inheritance, and that it’s because of inheritance that offspring have similar characteristic as parents.

• The bases for the law of segregation of genes which are later expressed in an individual if they have a dominating gene. 

Qns 7. What is the aim of Mendel's experiment? 

Ans −The main aim of Mendel's experiment is to −

• Determine if character or traits will always be recessive.

• If traits affect each other during inheritance or not.

• If traits are transformed by DNA or not.