Mendel's deviations

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Mendel's deviations

By | March 2006
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Essay Question

Mendel's law of heredity explains how inherited traits are passed on from generation to

generation. Through out his life he devoted much of his time and effort in order to understand the

genetics of his pea plants. After many breeding experiments Mendel came across many findings

which lead to the formation of : The law of segregation and The law of independent assortment.

The law of segregation includes the notion of dominant and recessive genes. The outcome relies

heavily on mere chance and probability. ( The Punnett-Square method was used to help visualize

the possibilities.) The law of independent assortment says that an organisms individual traits are

passed in independently of one another. Mendel observed that ratios were not always exact but he

did not put aside these deviations. The tendency of the loci on the same chromosome to remain

linked together during meiosis and gametogenesis is referred to as linkage. Autosomal linkage :

the loci are on the same chromosome, affecting the phenotypic and genotypic ratios of the

offspring. Recombination can affect linkage by separating the two parental loci, this occurs during

Prophase I of Meiosis. In sex linked ( X linked ) inheritance, alleles on sex chromosomes are

inherited in predicable patterns. Sex linked inheritance refers to those few recessive genes that

reside on the X chromosome. ( Females XX, Males XY ) Since males only have one X

chromosome, there is nothing to suppress the activity of the gene. Therefore, the affected gene is

expressed. Polygenic inheritance involves multiple genes that encounter no environmental

influence. Through extensive research it was found that traits of a cross tended to be intermediate

in appearance between the two parents. An example would be when a tall person crosses with a

short person the result will be a child with height that falls between the heights of the parents.