Why is it difficult to determine the genotype of an organism that has a dominant phenotype?

Answer 1

NO, because a dominant phenotype could either be homozygous or a heterozygous.so unless you are sure about the genotype of parents we can't determine it...but we can determine the genotype of a person showing reccessive phenotype, as a recessive trait always expresses itself in a homozygous condition...

Answer 2

Hybrid seeds are produce by the cross fertilization of two species which involve lot of research work and cost. Companies spend a lot of money on the research and development

of these seeds, It also takes a lot of time of their scientists. These factors add on to the price of their production.

Answer 3

Definitions: phenotype is the constellation of observable traits; genotype is the genetic endowment of the individual. Phenotype = genotype + development (in a given environment). To consider these in the context of evolutionary Biology, we want to know how these two are related. In a narrow "genetic" sense, the genotype defines the phenotype. But how, in and evolutionary sense, does the phenotype "determine" the genotype? Selection acts on phenotypes because differential reproduction and survivorship depend on phenotype. If the phenotype affecting reproduction or survivorship is genetically based, then selection can winnow out genotypes indirectly by winnowing out phenotypes.

Answer 4

To a degree, but it really depends on the particular gene you are considering. For example, in the case of genes with dominant and recessive alleles, if you observe a recessive phenotype, you can infer that the genotype must be two copies of the recessive allele. But if you see a dominant phenotype, you don't know whether the genotype is two copies of the dominant allele or one copy of the dominant allele and one copy of the recessive. That's why in classic genetic experiments, you do several generations of breeding - you can distinguish an homozygous dominant organism from a heterozygous organism by whether it ever produces offspring with the recessive phenotype.

In some cases, where there's incomplete dominance, or where haploinsufficiency, you can distinguish a heterozygote from a homozygote.

Answer 5

The dominant allele is always expressed if it is present. Therefore, an organism showing the dominant phenotype could either be homozygous dominant (2 dominant alleles) or heterozygous (a dominant and a recessive allele)

To be able to determine the genotype of a dominant organism, a test cross would need to be carried out which involves mating the organism in question with another organism which is a pure-bred recessive. If any of the offspring show the recessive phenotype, then the genotype of the organism in question is heterozygous. To be reliable, many offspring are needed.

Answer 6

If the individual is exhibiting a dominant trait it cannot be recessive so the question becomes whether the individual is heterozygous or homozygous for the dominant trait.

The three main ways are through testing, if it is available, pedigree analysis or breeding trials.

With testing the results are obvious.

Pedigree analysis can determine if the individual is heterozygous based on parents (if one parent is homozygous recessive then the individual can only be a heterozyote), analysis of ancestors and their progeny can help determine the probability that the target animal is homozygous.

Breeding trials would require a minimum numberof 7 strait offspring from homozygous recessive mates to yield a high enough probability to state that the individual is homozygous dominant.

Answer 7

To have a recessive phenotype, you need two recessive alleles. So to have a recessive phenotype, you must have a genotype of bb. 2 recessive alleles