Rabu, 27 November 2013

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Dihybrid Cross and Assortion Law

dihybrid cross  is a cross between  two organisms  involving  two distinct If monohybrid  cross produces  4 genotype with 3 : I ratio, dihybrid produces 16 genotype with  I : 3  : 3 : I ratio.

in dihybrid cross, Mendel  crossed  round yellow seed pure-breeding pea plants with wrinkled green  seed pea plants.  In this case, round seed is dominant to wrinkled seed  and yellow seed  is dominant to green seed. All the offspring of F, generation  have round yellow seed. When F1 generation undergo self-pollination,  they produce  four  types of Phenotype with  ratio 315 round yellow  seed:  108 round green  seed  : 101 Wrinkled yellow seed: 32 wrinkled  green seed. The ratio of F2 generations Can be simplified  into 9 round yellow  seed  : 3 round green seed  : 3 wrinkled Yellow seed:  1 wrinkled green seed.

Mendel I had analyzed that every  trait was bequeathed separately. The 3:1 ratio  in monohybrid  cross is seen separately  and it matches segregation law. The segregation between allele S and allele s must occur independently without influencing  or being  influenced by segregation process between allele Y and allele y. Since  the probability of round  yellow combination is bigger  (SSYY, SsYy, SsYY and  SSYy), then the phenotype often appears in F2, generations.  Look picture above!

Dihybrid cross of seed

Gregor Mendel (1882-1884) Genetics Pioner The basic low of genetic was first stated by gregor mendel, an Autrian, monk, in 1866. A Danish botanist, Johansen called the heredity factor in mendel’s experiment as gene (1909). In 1912, Thomas Morgan, an American scientist, explained that genes lay in chromosome. In this case, Morgan used fruit fly, Drosophila melanogaster as his study object.

According  to the result of the second experiment  in dihybrid  cross' Mendel  composed Mendel's Law  II that is known  as Lau of independent Assortment. Assortment law states that during gamete  formation,  each allele assorts  independently.  The definition of independent assortment  is that every male gamete  produced by F1, will have the same opportunity  to fertilize  female  gamete  produced by F1.
source: wikipedia.org

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