Experiment 2: Bateson and linkage

One of the pioneers of the scientific study of heredity was the Englishman, William Bateson (1861-1926).

He coined the term genetics and named the different versions of a gene, Mendel's factors, allelomorphs.   They are now known by the shorter form, alleles.

An organism that contains the same two alleles of a gene is homozygous for that gene.  If the two alleles are different, it is heterozygous.

Homozygous and heterozygous refer to specific genes; generally a organism is homozygous for some genetic loci (genes) and heterozygous for others.

The total set of alleles carried by an organism is its genotype. The specific properties of the individual organism are known as its phenotype.

Treasure your exceptions!  When there are none the work gets so dull that no one cares to carry it further. - William Bateson.  

In 1906 Bateson & Punnett studied two traits red/purple flower and round/elongated pollen, in the sweet pea Lathyrus odoratus

According to Mendel's rules, if we start with pure-breeding parental strains, mate them, and then perform a dihybrid F1 cross, the F2 generation should display the traits in the ratio of 9:3:3:1 -- the double dominant phenotype being most common and the double recessive phenotype begin the the least common

Experiment 2 : We have in our garden two pure breeding strains of L. odoratus, one is short, with red flowers and round pollen, the other is tall, with purple flowers and elongated pollen.   Devise a series of crosses to determine if all three traits display the expected Mendelian behavior in the F1 and F2 generations.

  • Use javaGenetics™ to perform your crosses.  Indicate which traits are recessive and which are dominant.   Record the results of your experiments and suggest a possible explanation for the observations your find. 

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