Q. 254.3( 3 Votes )
• Such type of inheritance in which more than two genes contribute for the phenotypic traits of an individual is known as Polygenic Inheritance.
• For example, let’s assume that the skin colour in humans is controlled by three genes, namely A, B and C.
• The dominant genes A, B and C are responsible for imparting dark colour to the skin.
• The recessive genes a, b and c are responsible for light skin colour.
• The genotype with all dominant alleles AABBCC will be darkest skin colour.
• The genotype with all recessive alleles aabbcc will be lightest skin colour.
• Whereas there is another genotype AaBbCc which imparts an intermediate skin colour. This because of the presence of three dominant alleles and three recessive alleles.
• The fragments of the DNA were sequenced using automated DNA sequencers.
• Thus obtained sequences were arranged based on some overlapping sequences present in them.
This alignment of sequences couldn’t be done by humans.
• As a result of this, computer based programs were developed for the purpose of aligning.
• These sequences were annotated and were assigned to each chromosome.
• Thus, the sequence of Chromosome 1 was completed.
• Caenorhabditis elegans was a free living non-pathogenic nematode who’s DNA has been sequenced.
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