Principles Of Inheritance And Variation

Answer (a) pleiotropic gene

Incomplete dominance is the case where Fj hybrids exhibited a mixture or blending of characters of two parents. It simply means that two genes of allelomorphic pair are not related as dominant or recessive but each of them express itself partially. For example in the case of Antirrhinum majus (snapdragon) and Mirabilis jalapa (4 Oclock plant).

Mendelian principles are based on sexual reproduction. Therefore, they are not applicable in case of asexually reproducing forms.

Mendel was successful in discovering the principles of inheritance as he did not encounter linkage between genes and for the characters he considered. One of his principles-independent assortment is applicable only if the genes are located on different non-homologous chromosome pairs.

Intermediate inheritance is incomplete dominance in which dominant factor of a heterozygote does not completely mask the expression of recessive allele. In incomplete dominance, genotypic and phenotypic ratio remain the same and is .

Crossing over is a process that produces new combination of genes by interchanging of segments between non-sister chromatids of homologous chromosomes. It occurs between homologous chromosomes at four standard stage during pachytene of prophase-I of meiosis-I.

Incomplete dominance is the phenomenon of neither of the two alleles being dominant so that expression in the hybrid is intermediate between the expressions of the two alleles in homozygous state. phenotypic ratio is , similar to genotypic ratio.

Incomplete dominance the genes of an allelomorphic pair are not expressed as recessive and dominant and is expressed themselves partially, e.g., plant like Antirrhinum, when the hybrid of , progeny are crossed among themselves to raise generation, they produce a phenotypic ratio of which is identical to genotypic ratio because heterogygote are phenotypically intermediate between homozygous types,

Since round seed shape is dominant over wrinkled seed shape and yellow cotyledon is dominant over green cotyledon so RRYY individuals is round yellow and rryy is wrinkled green.

The chromosomal disorders are caused due to lack or additions or abnormal arrangement of one or more chromosomes. Failure of segregation of chromatids during cell division cycle results in the gain or loss of chromosome , is called aneuploidy. For example, Down's syndrome results due to gain of extra copy of chromosome . Similarly, Turner's syndrome results due to loss of an chromosome in human females.