Definitions of some technical terms used in Mendel’s experiments ( Allele , Pleiotrophic gene , Genotype , Phenotype and more)

04/07/2020 Vinod 0 Comments

Allele or Allelomorph :-

Genes which code for a pair of contrasting traits are known as alleles, i.e. They are slightly different forms of the same gene.

Example – In case of the character of height, T is used for the tall trait and t for the dwarf, T and t are alleles of each other.

Hence, in plants the pair of alleles for height would be TT, Tt and tt.

Pleiotrophic gene :-

Genes which govern more than one characters of function is called pleiotrophic gene.

Genotype :-

Struture of genes of an organism is called genotype.

Example – TT, Tt and tt for height.

Phenotype :-

It is a physical expression of the genotype or external form of any trait is called phenotype.

Example – Tall for TT and Tt, Dwarf for tt, Round for RR and Rr.

Dominant characters ( traits ) :-

A dominant trait is an inherited characteristic that appears in an offspring if it is contributed from a parent through a dominant allele ( represent capital latter ). Traits, also known as phenotypes.

  • This trait will always be expressed in the offspring if the dominant allele is present even if there is only one copy of it ( heterozygous or homozygous )

Representation of dominant traits –

Aa ( heterozygous )

AA ( homozygous )

Recessive traits :-

A recessive trait will only be expressed of the recessive allele that codes for the trait ( recessive homozygous – aa, rr, tt etc )

Homozygous :-

If an individual carries the same two alleles for a gene, they are homozygous.

Example – aa, AA, TT, tt etc.

Heterozygous :-

If the two alleles are different, the individual is called heterozygous.

Example – Aa, Tt, Rr etc.

First generation or F₁ – generetation :-

The generation formed by the hybridisation ( cross ) between two parents is called first generation.

Second generation or F₂ – generation :-

The generation formed by the cross between two organisms of F₁ – generation is called F₂ – generation.

Emasculation :-

The process of pik-out to the anther from a flower before maturation is called Emasculation.

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