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Genetic Inheritance Cont… 10/20/2011

20 Oct

We continued to discuss genetic inheritance but this time in greater detail. To throughly understand the concept of inheritance you must first know the difference between a genotype and phenotype. Genotype of a person is the varied genes of a certain trait that you possess along your chromosomes where as the phenotype is the expression of the gene or trait; in simpler terms, phenotype is how you look. Geneticists use punnette squares to show the probability of an offsprings to acquire a particular genotype which will essentially effect the offsprings phenotype. A punnette square can only be used to determine the probability of an offsprings acquiring ONE trait!

If you wanted to determine the acquisition of multiple traits then the best graph to use would be the dihybrid crossing graph.

Although, Gregor Mendal made genetics seem like a simple mathematical equations,9:3:3:1, governed by easy probabilistic occurrence,genetics is far from simple because traits of one characteristics of a person could rest on the same chromosome. Hence, they are not independently assorted whereas traits that are not on the same chromosome are independently assorted, or randomly given to offsprings.

When looking into inheritance, one must take into consideration the fact that some traits display incomplete or codominance characteristics. Incomplete dominance occurs when two parent organism mate and they pass to the offsprings to separate alleles and neither alleles shows complete dominance or expression over the other. In other words, there is a blending of the alleles when the phenotype of the offspring is expressed.

Codominance can also occur. When two parent come together and they pass to the offspring separate alleles that are both dominant and the offsprings expresses both proteins instead of one over the other. The most common example of codominance is blood types. Those individuals that have the AB blood type are the perfect example of an organism expressing codominance. The have the genes to produce both the A and B red blood cell antigen and not just either A or B or no antigen.

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Posted by on October 20, 2011 in Uncategorized

 

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