Category «Genetics»

Rieger Syndrome

Definition Rieger syndrome is a rare disorder characterized by absence and/or malformation of certain teeth, mild craniofacial (relating to the head and the face) abnormalities, and various eye abnormalities. The eye abnormalities, referred to as Rieger eye malformations, may be present separately or as a part of Rieger syndrome. Description First characterized by Herwigh Rieger, …

Lethal Genes

The term ‘lethal’ in genetics is applied to those changes in the genome of an organism that produces effects severe enough to cause death. The fully dominant lethal allele  kills the individual both in in its homozygous and heterozygous conditions. The individuals with dominant lethal allele die before they can produce progeny. Therefore, the mutant …

Codominance

In the phenomenon of co dominance, dominant and recessive alleles lack typical dominant and recessive relationships. In the heterozygous conditions both the alleles of genes are capable of expressing themselves and therefore in the heterozygote, the traits occur side by side. The F2 progeny shows the phenotype and genotypic ratios of 1:2:1. The best example …

Incomplete dominance

Modification of monohybrid ratio: The mono hybrid phenotypic ratio of 3:1 occurs only in process in which the alleles have a relationship of dominance and recessiveness between each other, in the absence of such a typical allelic interrelationship, the 3:1 phenotypic ratio is variously modified as described below: 1) Incomplete dominance: When alleles of monohybrid …

Laws of Heredity

  Law of segregation or Law of Purity of gametes: The factors are separated during gamete formation, each gamete having only one factor and which is not influenced by the other factor though both had remained together (Now, this is called the first law).  Law of independent assortment: Factors for different characters behave independently. No …

Mendelian Principles

Johann Gregory Mendel was an Australian monk, who conducted several experiments with pea plants in the garden. He found several contrasting characteristics in pea plants such as tall and dwarf plants, yellow & green cotyledons, and round and wrinkled seeds etc. These characters occurred repeatedly generation after generation because pea plants are self pollinated. In …

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