3. Carotenoids are a group of pigments found in many plant species. They are for

Question

3. Carotenoids are a group of pigments found in many plant species. They are formed via the terpenoid pathway. Lycopene (Lyc) is a red colored pigment, carotene (Car) is orange and Lutein (Lut) yellow. The precursor molecules are colorless. See figure 1.

a. Red flower color in Coneflowers is dominant to white.

i. What symbols would you use to represent the genotypes of a heterozygous red flowered plant and a white flowered plant?

ii. What would the expected phenotypic ratios be in a cross of these parents?

b. Red flowered cone flowers x white flowered ones leads to yellow flowered coneflowers. What would explain this, that is how would genotype link to phenotype – look at the figure?

c. It is actually easier to map this as a two-locus interaction (see Labradors in the book). If you crossed F1 plants that were heterozygous at both loci, what would the genotypes and phenotypes be in a population of 100 progeny?

Explanation / Answer

a) i. Genotypes of heterozygous red flower plant is – Rr

       Genotypes of white flower plant is – rr

ii. Cross between these above two parents :

Rr        X          rr ...........................Parent

         Rr    rr    .................................F1

So, in F1 generation we can see here heterozygous red flower(Rr) and white flower(rr) will produce.

Now phenotypic ratio is 1:1.

b) Red flowered cone flowers x white flowered ones leads to yellow flowered coneflowers.

It is happen because of the co-dominance. In co-dominance, an additional phenotype is produced, however, both alleles are expressed completely.

As, here we see that cross between a red flowered cone flower and white flowered cone flower produce a yellow flowered cone flower, so as an effect of co-dominance an additional phenotype yellow colour is produced.

c) Cross between two heterozygous flower –

Rr                  X                    Rr ................................................Parent

        RR     Rr      rr     .............................................................F2

In F2 generation Red, Red(heterozygous) and white are produce in 1:2:1 raio.

So, in a population of 100 progeny pure red flowered cone flowers will be – [(1/4)*100]= 25

Red(heterozygous) flowers will be – [(2/4)*100] = 50

And White flowers will be – [(1/4)*100] =25

d) Yes, it is possible to have an orange flowered cone flower because of co-dominance.

In this case, it will dominant.

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