Autosomal+Linkage

__Autosomal Linkage__


 * __Collaborative Notes:__**


 * Autosome**: Any chromosome not considered as a sex chromosome, ie) is not involved in sex determination. A human somatic cell will normally contains 23 pairs of chromosome, twenty-two of these pairs will be autosomes.


 * Autosomal Linkage**:Refers to genes being on the same chromosome,these genes tend to show up together in the same combinations in the offspring.

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Genes on the same chromosomes are said to be linked. They cannot segregate independently at meiosis. Their mode of inheritance is an exception to Medel's Second Law.

Law of Segregation : "of the two genes controlling each characteristic, only one is present in each gamete" Mendel's First Law. Law of Independent Assortmen : "the segregation of one pair of alleles does not affect the segregation of another pair" Medel's Second Law.
 * Mendel's Law :**

If genes on the same chromosome were permanently stuck together they would be inherited as a single indivisible package and could not be reshuffled into new combinations. An organism heterozygous for two pairs of alleles would behave like a monohybird, producing only two kinds of gamete instead of one.

__**Crossing Over:**__ New combinations of alleles are produced by crossing over, which occurs during meiosis 1. Before crossing over occurs, the two sister chromatids of each chromosome are genetically indentical. Two parental types and two recombinants are produced as the result of crossing over.

The cells in which there is a crossing over between linked genes would produce 4 types of gamete in a 1:1:1:1 ratio. The cells in which a crossover elsewhere (ie no crossover between the linked genes) would produce two kinds of gamate in a 1:1 ratio.

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