German abbot Gregor Mendel published his famous pea results in 1866, to what can

Question

German abbot Gregor Mendel published his famous pea results in 1866, to what can be described as a general shrug. Fast forward 35 year when two scientists, Hugo de Vries and Carl Correns, independently arrived to the same conclusions and rediscovered his work. This would catch the general attention and eventually redefined the fields of genetics, evolutionary biology, and population genetics.

In 1904, William Bateson, Edith Saunders, and Reginald Punnett (of the Punnett square fame) published odd results: when selfing pea plants investigating pollen shape and flower color, the F2 generation deviated dramatically from the Mendelian 9:3:3:1 ratio expected of the F2 generation looking at 2 traits:

Discuss how and why those numbers deviate from Mendelian expectations (i.e is there any pattern of divergence in the data ?; what might be causing this divergence?) Why are these surprising or not surprising? Note that purple flowers and long pollen are the dominant phenotypes, while red flowers and round pollen are recessive.

PLEASE DISCUSS IN WORDS =)

Phenotype Observed Expected Purple, long 1528 1199 Purple, round 106 400 Red, long 117 400 Red, round 381 133 Total 2132 2132

Explanation / Answer

Answer: Suppose, P = allele for purple flower trait (dominant), p = allele for red flower trait (recessive); L = long pollen trait (dominant) and l = round pollen trait (recessive).

Now, according to Mendelism selfing of a PpLl will have offspring phenotype ratio as below:

Purple-Long: Purple-Round: Red-Long: Red-Round = 9:3:3:1 ... among which, Purple-Long and Red-Round are phenotype being resulted from parental genoytype containing germs (or, non-Recombinant germs), while Purple-Round and Red-Long are offspirng, being resulted form cross over (or recpmbinant) genotypes.

Observed ratio is indictaing a reduced recombinant phenotypes than expected. Thus it could be concluded that ther is some amount of Linkage, present, betwwen these two locus (i.e. betwee locus of flower colur and polen shape). This linkage phenomenon is reducing the expected amount of recombination between these two locus, resulting a low ratio of recombinant offsprings.

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