Question

What determines the single characteristics of an organism?

Answer 1

Hint: A trait is a specific characteristic of an organism that can be determined by genes or the environment, or by interactions between them. The genetic contribution to a trait is called the genotype and the outward expression of the genotype is called the phenotype. DNA contains all the information needed to build our bodies. Our DNA determines things such as our eye color, hair color, height, and even the size of our noses.

Complete answer:
The term "phenotype" refers to all the observable physical properties in an individual organism; it includes the organism's appearance, development, and behavior. An organism's phenotype is determined by its genotype. Genotype is the set of genes that the organism carries.

As phenotype is also influenced by environmental factors, sometimes organisms with identical genotypes, such as identical twins, ultimately express nonidentical phenotypes because each organism encounters unique environmental influences as it develops. Examples of phenotypes include eye color, wing length, and hair color, etc. Phenotypes also include observable characteristics that can be measured in the laboratory, such as the amount of levels of hormones or number of blood

The phenotype is the total characteristics displayed by an organism that results from the expression of the genes of an organism as well as the influence of environmental factors and random variation. The interaction between these factors has often been represented by the following relationship:

genotype+environment+random variation = phenotype.

So a single characteristic of an organism is determined by its phenotype, which is the combination of genotype, environment, and random variations. That is why in genetics the trait. The phenotype of an organism is composed of different traits, for example- the hair color is a character in which the traits could be black, blonde, ginger, or brunette.

When the pair of alleles determining a particular characteristic consists of the same genes e.g. AA or aa, the trait is said as homozygous and when the allelic composition consists of different genes, e.g. Aa, the trait is said to be heterozygous. The presence of the dominant allele, i.e. AA or Aa, will result in the expression of the trait (A) whereas the absence of the dominant allele, i.e. aa, will result in the expression of the other trait (a), this is a case of complete dominance and it follows the Mendelian inheritance. In cases of codominance, incomplete dominance, and polygenic inheritance, the expression of a trait will not follow the Mendelian pattern.

For example, in codominance, the alleles of a gene pair in a heterozygote will be fully expressed since both alleles in a pair are dominant (e.g. AB). In incomplete dominance, the resulting trait will be an intermediate of the effects of the two alleles; this happens because the dominant allele will only be partially expressed as a result, heterozygous offspring will show a phenotype that is intermediate to the phenotype of the parents.

Note:
Other than genetic factors, exposure to environmental factors could affect the appearance of an organism. For example, a light-colored skin that is constantly exposed to the sun’s rays will cause the skin to darken from increased melanin production. In case of random variation, the genetic mutation could alter the physical trait or at least the fitness of an organism.