Inheritance Definition: Meaning, Synonyms, Issues, & Facts

Inheritance is the process by which traits are passed from parents to offspring through genes. It forms the basis of heredity and explains why offspring resemble their parents. The study of inheritance involves knowledge of genetic principles like Mendel's laws, dominant and recessive traits, and variations caused by genetic combinations. In this article, inheritance definition, basic concepts of inheritance, Mendelian Inheritance, Non-Mendelian Inheritance, and Sex-linked Inheritance are discussed. Inheritance is a topic of the chapter Principles of Inheritance and Variation in Biology.

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This Story also Contains

1. Inheritance Definition in Biology
2. Basic Concepts of Inheritance
3. Mendelian Inheritance
4. Non-Mendelian Inheritance
5. Sex-Linked Inheritance

Inheritance Definition in Biology

Biological inheritance is a process in which genetic information is passed from parents to offspring. Put differently, the transfer of traits from one generation into the following takes place through genes, which are described to be the basic units of heredity. Understanding inheritance is therefore important if one needs to understand how traits and characteristics are passed on to cause variations within a species.

Inheritance is the basis for the major field of biology known as genetics, which is tailored to variation and the transmission of traits.

The study of inheritance allows prediction regarding the patterns of traits and accounts for particular disorders genetically transmitted in families due to abnormalities of the genetic material. It also finds application in techniques of genetic engineering for health and agriculture. The basic principles of inheritance form the basis of advances in medicine, biotechnology, and evolutionary biology.

Basic Concepts of Inheritance

The concept of inheritance is described below:

Genes and Chromosomes

Genes are short stretches of DNA that encode proteins, which determine the expression of certain traits. They are located on chromosomes, which are long helices of DNA wrapped around proteins called histones. There are 23 pairs of chromosomes in humans, with each one containing thousands of genes. Chromosomes ensure the proper distribution of genetic material during cell division and hence may be considered responsible for heredity.

Alleles

Alleles are the variants of genes that produce variation in a given trait. Dominant alleles mask the presence of other alleles, although sometimes allele expression is only seen if the organism has two copies of the allele. For example, the allele for purple flowers, P, is dominant over that for the white version, p, at the same locus in pea plants. An individual who contains two copies of the same allele for a given trait is homozygous (PP or pp). An individual who contains different alleles at a particular locus is heterozygous; in this case, that would be Pp.

Genotype and Phenotype

Genotype refers to the genetic constitution of an organism, that is, all its genes and alleles. The phenotype is the expression of the genotype resulting from the interaction of the genotype with environmental factors. In pea plants, the PP or Pp genotype will produce the phenotype known as purple flowers and the pp genotype will produce white flowers.

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• MCQ Practice on Inheritance
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Mendelian Inheritance

The Mendelian Inheritance is given below:

Laws of Mendelian Inheritance

Gregor Mendel, the Father of Genetics, formulated laws of inheritance based on his experiments with pea plants. The Law of Segregation says that as gametes are made, the two alleles for a given trait separate, and thus each contains just one allele. The Law of independent assortment states that during the formation of gametes, alleles segregate separately, resulting in each possible genetic combination.

Monohybrid Cross

A monohybrid cross is a cross for a single trait. All possible genotypes and phenotypes that will result in offspring from parents of known genotypes can be predicted using a Punnett square. Such as crossing homozygous dominant (PP) with homozygous recessive (pp) will yield all heterozygous offspring (Pp) with the dominant phenotype.

Dihybrid Cross

A dihybrid cross-examines two traits simultaneously. A Punnett square for a dihybrid cross is larger because it includes all possible combinations of alleles for both traits. For instance, crossing plants heterozygous for the seed shape (Rr) and seed colour (Yy) gives offspring in the ratio 9:3:3:1, a result that describes Mendel's Law of Independent Assortment.

Non-Mendelian Inheritance

The Non-Mendelian Inheritance is given below:

Incomplete Dominance

Incomplete dominance is a phenomenon where the expression of the heterozygous phenotype is an intermediate mixture of two homozygous phenotypes. For instance, in snapdragons, crossing the flower colour with red (RR) with white (rr) results in the pink colour in the offspring, Rr.

Codominance

In codominance, both alleles are expressed fully in the heterozygote. The classical example is the ABO blood group system in human beings. For example, I^A and I^B alleles produce A and B antigens on the red blood cells and result in AB blood type.

Multiple Alleles

Multiple alleles refer to the presence of more than two alleles of genes in a population. Inheritance of blood group systems ABO typifies this, whereby three alleles (IA, IB, i) determine four blood types: A, B, AB, O.

Polygenic Inheritance

Polygenic inheritance is a condition where more than one gene controls a particular trait, causing continuous variations. Skin colour in human beings is a polygenic character controlled by several genes which contribute to the gradation of skin colours found amongst the population.

Sex-Linked Inheritance

The Sex-linked Inheritance is described below:

Sex Chromosomes

Sex is determined by the sex chromosomes, X and Y. For sex determination to take place, what is required is that females must have two X's, while males should be XY. These contain genes for sex-linked characteristics.

X-Linked Inheritance

X-linked inheritance refers to genes on the X chromosome. Specific disorders such as colour blindness and haemophilia are more common in males than females since there is only one X chromosome, carrying a single recessive allele of some genes on the X chromosome that expresses the trait.

Y-Linked Inheritance

Y-linked inheritance refers to genes on the Y chromosome. Y-linked genes have a transmission pattern of father to son. Traits controlled by Y-linked genes are very rare and usually involved with male-specific development.

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