Phenotypic trait

A phenotypic trait is the state of an observable characteristic or behavior of an organism that is determined by its genetic makeup and the influence of its environment. Size, color, and shape are examples of phenotypic traits. The largest influence on these traits is genetic ancestry, but errors in the genetic copying process and the environment also play a role in the appearance of living things. Researchers have also discovered that some phenotypic traits are related to specific health conditions.

Background

All the characteristics of any living thing are determined by deoxyribonucleic acid, or DNA. DNA is the genetic code, or set of instructions, for the organism. The genetic code establishes what the organism will be, how it will look and move, and a number of other characteristics.

The physical traits and behaviors of any organism are determined by genes, which are pieces of the longer strands of DNA. The genes are found on parts of the DNA called chromosomes. Different organisms have specific numbers of chromosomes, and these chromosomes come in pairs.

Many traits come in different forms. For example, eyes come in different colors, or an organism can be larger or smaller than average. The genes that determine which of the possible forms will be shared are called alleles, and they are located on specific spots on the chromosomes. The majority of living organisms receive half of their total number of chromosomes and their related alleles from each parent during the reproductive process.

The way these alleles combine determines each characteristic. The alleles inherited from the parents can be the same or different. When the alleles are the same, the organism will have one phenotype for that trait. When they are different, the organism will have more than one phenotype. Some of these alleles will be dominant, or take precedence over the others. For example, the alleles for brown eyes take precedence over those for other colors. Other traits are recessive. The alleles for blue eyes are recessive. This means they do not take precedence over other traits, and two alleles for blue eyes are necessary for the person or animal to have blue eyes.

Sometimes, unexpected changes or mutations occur when genes are passed from one generation to the next. This can cause new variations to develop. The introduction of new organisms to the gene pool can also cause changes. For example, when dogs of two different breeds have puppies, the puppies will have new traits that will then be passed on to future generations. New versions of genes can also occur through a process known as crossing over, when small segments of the gene pairs switch places.

Overview

Living organisms are identified by their class and type. These can be broad categories, such as plant or animal, or more specific, such as a tree or a mammal. Classifications can become even more specific, such as a maple tree or a dog. Within these classifications, there are even more specific groupings, such as a red maple or a Labrador retriever. The characteristics that separate and define each of these categories or classifications are based on phenotypic traits.

These phenotypic traits are genetically inherited from the parent organisms. The phenotypes that can be inherited are determined by the parent organisms’ genotypes, or the part of the DNA that they share with the offspring. Each individual offspring inherits a different set of genes from the parents, so each offspring will have a different phenotype.

The word trait is sometimes used interchangeably with the word phenotype. This is not completely correct. A trait is the type of characteristic, such as height or eye color. A phenotype is the form that trait takes that can be observed, such as being six feet tall or having green eyes. A phenotype is, therefore, the visible and observable expression of the genetic material that has been passed from the parent organism to the offspring.

Different organisms have different amounts of possible options for phenotypic traits. For example, people can have a number of different colors of eyes while some breeds of animals only have brown eyes. This is because people have a wider variety of alleles that can be inherited, while many animals have a more limited range of eye color alleles.

While phenotypic traits are based in genetics, these traits can be altered by other factors. These include genetic mutations and crossover genetics. Environment can also play a role in the expression of some phenotypic traits. For example, the height of humans can be affected by diet and disease while available food, water, and sunlight affect the growth of plants.

The expression of these traits can also be manipulated to some degree. Many plants and the flowers, fruits, and other things they produce are the result of alterations that have occurred over time. This can occur naturally as plants with different phenotypes are crossbred. For instance, two different types of apples can be crossbred when bees, wind, or some other natural force carries pollen from one to the other. This can also be done intentionally by humans who seek to develop a plant or animal with specific characteristics. Many dog breeds have been bred to have specific traits, such as skill in hunting or the ability to dig. This is done by choosing two plants or animals that have the desired trait and breeding them with the intention that the resulting offspring will demonstrate the desired phenotypic trait.

Bibliography

“The Genotype/Phenotype Distinction.” Stanford Encyclopedia of Philosophy, 6 June 2017, plato.stanford.edu/entries/genotype-phenotype/. Accessed 3 Dec. 2018.

Newman, Tim. “What Is DNA and How Does It Work?” Medical News Today, 11 Jan. 2018, www.medicalnewstoday.com/articles/319818.php. Accessed 3 Dec. 2018.

“Phenotype and Genotype.” Brown University, biomed.brown.edu/Courses/BIO48/5.Geno.Pheno.HTML. Accessed 3 Dec. 2018.

“Six Things Everyone Should Know about Genetics.” American Society of Human Genetics, www.ashg.org/education/everyone‗2.shtml. Accessed 3 Dec. 2018.

“Trait (biology).” Science Daily, www.sciencedaily.com/terms/trait‗(biology).htm. Accessed 3 Dec. 2018.

“Variation and Inheritance.” BBC, www.bbc.com/bitesize/guides/z2xbh39/revision/1. Accessed 3 Dec. 2018.

“What Are Phenotypes?” 23 and Me, www.23andme.com/gen101/phenotype/. Accessed 3 Dec. 2018.

“What Is a Phenotype?” Warwick Crop Centre, warwick.ac.uk/fac/sci/lifesci/research/vegin/geneticimprovement/phenotype/. Accessed 3 Dec. 2018.