Mendelism:
- Mendelism is a term that refers to the single-gene trait's theoretical principles of heredity, which are taken from Gregor Mendel's principles, also known as Mendel's laws.
- Gregor Mendel conducted several experiments on pea plants for seven years and then postulated the laws of inheritance.
- Mendel's law of inheritance includes the law of dominance, the law of segregation, and the law of independent assortment.
Law of dominance:
- The first law of inheritance is the law of dominance.
- The law states that hybrid offspring will only inherit the dominant characteristics in the phenotype.
- The alleles that suppress a trait are recessive traits, whereas the alleles that define a trait are known as dominant traits.
- Monohybrid cross helped in proposing the law of dominance.
- In a monohybrid cross, Mendel crossed two pure pea plants with opposing traits (one short and one tall).
- Mendel named those first-generation offsprings as F1 progeny and all the offspring produced by crossing tall plants (dominant trait) and dwarf plants (recessive trait) were tall ( heterozygous dominant or hybrid).
- After that, Mendel crossed F1 progeny, and both tall and dwarf plants were obtained in the F2 generation.
Law of segregation:
- The law states that every pair of alleles or genes in parents, divides and a single gene is transferred from each parent to their offspring. The passage of a particular gene in a pair is a chance event.
- There are several alleles for a single gene.
- Every organism inherits a pair of alleles for each gene.
- During the process of gametogenesis, when gametes are produced by meiosis, Then the allelic pairs segregate, leaving each gamete with only one allele.
- A gene has two alternate forms known as alleles. One allele is dominant while the other allele is recessive.
Law of independent assortment:
- According to this law, discrete pairs of alleles pass onto the children without being dependent on one another and as a result, the inheritance of genes in a particular region of the genome has no effect on the inheritance of genes in another region.
- A dihybrid cross was used to formulate the law of independent assortment.
- In a dihybrid experiment, Mendel selected two traits, each with two alleles.
- He crossed round-yellow seeds (dominant) and wrinkled-green seeds (recessive) and observed that all of the F1 progeny were round-yellow.
- He then self-pollinated the F1 progeny and obtained four distinct phenotypes that are round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds in the phenotypic ratio of 9:3:3:1.