Explain how the passage of genes from parents to offspring, in the form of particular alleles, ensures perpetuation of parental traits in offspring and, at the same time, genetic variation among offspring.

Generally the genetic composition of every individual are conserved in the DNA, which are expressed as Genes. The part of DNA that codes fro a particular protein is called Gene. These genes were inherited from individual parents by offspring  during genetic processes, and are  passed to next generation of  initiated by the offspring.Therefore the  type of  characteristics  or traits manifested by  an individual are results of gene expressed in DNA.

These traits are usually encoded as transcribed bases in mRNA, and when fully  translated they are expressed as  proteins . Thus  each  trait are  translated protein. This  explains   the forms of transport of genetic materials from parents to offspring.

The inherited traits can expressed itself fully in the offsping irrespective of other characteristics, e.g a white man who marries a black woman and all the kids are white with long hair, shows dominance of the  white  allele, expressed as protein,  despite the presence of the black allele. such black allele is said to be recessive.

The  independent assortment of genes at meiosis, the crossing over at prophase 1, and separation  of the chromosomes at Anaphase 1 and II together with random fertilization  by million of  genetically  varied  haploid sperm cells ensured that no  two individual are 100 % genetically identical even if they are from the same parents.  

The crossing over of genetic materials ensures  mixing of these material to give a genetically unique organisms  from mixture of the parents DNA. In addition the independent assortment of genes ensures that homologous chromosomes do not continue their 'journey' into the same sex-cells, and therefore the genetic component of the new sex-cells (sperm or oocytes ) and the resultant offspring varies

Furthermore, segregation of genes into different sperm cells   and eggs cells ensures  random distribution of the DNA in million of sperm cells and therefore varied traits because this DNA distribution can not be the same in each sperm or egg cells, ensuring great variation in the eventual offspring.

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