Unformatted text preview: recessive.
Why? Figure 2. Mendel’ dihybrid and trihybrid crosses. Mendel used these crosses to establish the principle of independent assortment.
s Example 1: Loss of function mutation The gene and the chromosome it is on are shown beneath the dominant allele in each cross.These are the only dihybrid and trihybrid
crosses that Mendel reported. In both dihybrid crosses, Mendel used genes on different chromosomes; as expected, these genes
assorted independently. In the trihybrid cross, Mendel used three genes. One of these, r, is on chromosome 5 and assorts independently
of the other traits.The other genes, I and a, are both on chromosome 1 but are located at 110 cM and 40 cM, respectively. Since they are
70 cM apart, there is 70%crossing-over between them, so they assort independently even though they are on the same chromosome.
Note:“ y Seed Coat”and“ iolet-red Flowers”refer to the a locus, the same locus as Purple Flowers.This is an example of pleiotropy.
The A allele results in purple (red-violet) flowers and gray seed coat, whereas the a allele results in white flowers and white seed coat. example 1: pheide a oxygenase (PAO)
•breaks down chlorophyll in peas as they mature T o i ll u st r at e t h i s, I sh o w m y st u d en ts a p ictu re o f fiv e g en etically
sh o r t c ab b ag e p lan ts. G ib b erellin h as b een ad d ed to th e t...
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- Fall '12
- Mutation, wild type