mendeleev's experiments...

Asked by  | 26th Mar, 2009, 08:36: PM

Expert Answer:

A phenotype is any observable characteristic of an organism such as its morphology, development, biochemical or physiological properties etc. It is the result of that individual's genotype and the interaction of the genotype with the environment during development. Hence, individuals with the same genotype may have different phenotypes in different environments.

 

Genotype is the genetic makeup of an organism. The genotype determines the hereditary potentials and limitations of an individual.  Among organisms that reproduce sexually, an individual's genotype comprises the entire complex of genes inherited from both parents.

 

 

To explain how to make F1 and F2 progeny, we will use the following example:

Let us cross a pure-breeding round-seeded variety of pea with a pure-breeding wrinkled-seeded one (RR for round; rr for wrinkled).

All the gametes of RR plant will carry 'R' factor whereas all the gametes of rr plant will carry 'r' factor or gene.

So when crossed, all the peas of this F1 generation have an Rr genotype.  All the zygotes received one R allele (from the round parent) and one r allele (from the wrinkled parent). Because the round trait is dominant, the phenotype of all the seeds was round.

    P gametes (round parent)
    R R
P gametes
(wrinkled parent)
r Rr Rr
r Rr Rr

Next, allow  this hybrid peas to self-pollinate.

 

    F1 gametes
    R r
F1 gametes R RR Rr
r Rr rr

Random union of equal numbers of R and r gametes produced an F2 generation with 25% RR and 50% Rr - both with the round phenotype - and 25% rr with the wrinkled phenotype.

 

Answered by  | 27th Mar, 2009, 11:06: AM

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