Genetics- genes & alleles

Genes are the fundamental units of inheritance which have the function of transmitting information from generation to generation. They are found on the portion of DNA that codes for polypeptide. Similar to genes are alleles which are the alternative form of a gene. However an allele can exist in more than two pairs.

Dominant Gene:- Is one that shows its effect in the phenotype in both homozygous and heterozygous conditions.
Recessive Gene:- A  gene that only expresses itself when in homozygous conditions.

Homozygous Vs Heterozygous

Homozygous refers to two identical alleles found on the same chromosome  while heterozygous refers to alleles that are unidentical.

Mono-hybrid Inheritance:

This is inheritance involving only one pair of contrasting characteristics.

Types of mono-hybrid inheritance:

Complete Dominance

1. Complete Dominance:- This is where the dominant gene shows its effect more in the phenotype (75% in offsprings to be exact).

Characteristics of Complete Dominance:

• Phenotypic ratio->> 3:1

• Genotypic ratio->> 1:2:1

• Both parents possess the same genotype and are heterozygous.

Incomplete Dominance/Codominance

In incomplete dominance each allele has the ability of expressing itself to some extent when in the heterozygous condition.  This is because of intermediate alleles, which are alleles which lask dominant and recessive relationship.


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