Everyone looks different: some people have curly hair while others have straight hair. Other characteristics such as the color of the eyes or the shape of the face also differ from person to person. In biology, the morphological and physiological appearance of an organism is summarized under the term «phenotype».
Phenotype – Definition
Under the phenotype or phenotype refers to all recognizable characteristics of an organism that contribute to its appearance. This can be about morphological or physiological properties, but also behavioral properties. Overall, the phenotype is determined by genetic factors (genotype) and environmental influences.
In general, the phenotype is composed of two factors. On the one hand, the genotype is decisive for the characteristics and characteristics of the phenotype. The genotype is made up of all of the genes that form the genetic information of an organism. The environment is also a decisive factor for the appearance of an organism, because environmental influences can affect genes and chromosomes and lead to their modification. This is also referred to as epigenetic modification.
Phenotype example
Plants are studied for the color of their flowers. There are two forms: the red flower (R) and the white flower (w). If you now cross these two plants with each other, the first daughter generation will all get the same genotype, namely “Rw” or “wR”. This means that all flowers of the daughter generation have the same red colouration, since the allele «R» is dominant over the allele «w» and prevails in the phenotypic expression.
phenotype:WhiteRedgenotype:wwRR, Rw
In this example, the F1 generation, the daughter generation of the white and red flowers, has only one phenotype. This is because the color white is recessive, while red is dominant. All four plants show a corresponding red flower colouration. Due to the uniform phenotype, conclusions can now be drawn about the genotype.
The inheritance in this example follows Mendel’s first rule – the uniformity rule. If you want to know more about it, feel free to check out the article on Mendel’s rules as well.
determine genotype
Of the genotype is the combination of alleles that determines the expression of a trait (e.g. flower color). It therefore represents the genetic basis of the phenotype.
If an individual has two of the same alleles of the gene that determines the trait under study, the individual’s genotype is referred to as homozygous (homogeneous). If there are two different alleles of the gene, it is called one heterozygousin (mixed) Genotype.
In the example given above, it is recognized that the red flower must be a dominant allele, since all daughter plants have this expression. Therefore, the phenotype is described as red and the associated dominant allele is described as “R”. On the other hand, the expression of a white flower is described with “w”.
In general, when describing dominant and recessive alleles, the Large and lower case important. Both alleles are described with one letter – in this case “R” or “w”. The dominant gene is always described with a capital letter. On the other hand, a recessive allele is always described with a lower case letter.
Since all plants of the F1 generation have red flowers, the red plant of the P generation must be homozygous. Therefore, both alleles of the genotype are labeled “R”. You can also conclude that red is the dominant flower color.
You want to learn more about the genotype? Then also read the summary of the genotype!
Phenotype in trisomy 21
Trisomy 21 is a genome mutation that results from the 21st chromosome being present three times. Affected individuals exhibit a specific phenotype characterized by the following characteristics:
- short stature
- Delayed development in puberty
- Weak muscles, loose connective tissue
- Hands with broad, short fingers and four-finger furrow
- Narrow, high and pointed palate and an overly large tongue that often sticks out of the mouth
phenotype in blood groups
Different phenotypes can also occur in relation to a person’s blood group. The blood group itself is inherited from parents to children. The rule here is that blood groups A and B are dominant over blood group 0. A and B, on the other hand, are inherited equally. Blood groups A, B, AB and 0 can appear as phenotypes.