Have you ever wondered about your eye color, skin color or some other physical features you have? How did you inherit those and how is that possible? Genetics have the law called Mendelian inheritance which was set by Gregor Johann Mendel in 1855/66. It was when he conducted experiments with peas which he planted himself. He tested about 5000 pea plants where he observed the shape and the color of the pea seeds. He combined the wrinkled with rounded ones and also green with yellow ones. He had proof about genotype and phenotype examples and changes which have occurred.
Phenotype. It represents the physical traits which are visible to a human’s eye. It means literally how the observed object will look like. So Mendel got a few phenotype groups:
- Ones with wrinkles and green color
- Rounded with green color
- Wrinkled with yellow seeds
- Rounded with yellow seeds.
Other than peas, he also did some experiments with the color of the flower and the heights of the plant. He did get some interesting results. He saw that some of the plants which he got as a product had the physical traits which were different from its source. So, some of the flowers had the third color as a result.
Genes are the information keepers which are being transmitted from each of our parents or from each of some other species, either a plant or an animal. Every chromosome has two alleles which make a pair. It can be homozygote and heterozygote. Homozygote has only one type of allele, such as HH or hh. Heterozygote has each member of the gene pair, such as Hh.
When describing the dominance between the alleles of the gene pair, it can be dominant or a recessive one. The dominant will prevail the recessive effects, meaning that we will have only dominant trains in phenotype. Recessive ones are going to show only if the dominant allele is not present. This is a complete dominance law. There are three types of dominance:
- Complete Dominance. This happens when the dominant allele is expressed and the recessive does not show even a bit. This is a full dominance over a recessive one.
- Co-Dominance. This is present when the both of the allele, dominant or recessive ones are fully expressed but do not overlay each other in compare to the complete dominance. They do not interfere, but they act together.
- Incomplete Dominance. This type of dominance has a feature of not fully expressing the present alleles in heterozygote pair. It has the both traits, but not in a full penetrability.
It is a type of intermediate inheritance where neither of the two expresses their traits to the full capacity. It is expressed in a phenotype which has the both features expressed but in a subtle way. But, what is the difference between the co-dominance and incomplete dominance? They feel similar, but they express differently. In co-dominance, both alleles are expressed completely, giving the new phenotype. As an example, this is presented in an AB blood type inheritance. B blood type can have two genotypes (B0, BB), depending if it’s a heterozygote or homozygote. An incomplete dominance is different where the alleles are not expressed completely.
Incomplete Dominance Examples
- A child with a wavy hair and parents where the one has a straight hair and the other has a curly hair.
- A child with a medium dark color of the skin, coming from parents where one has a pale or white skin color and the other one has a brown skin color.
- A child with a medium pitch voice having parents, one with a high-pitched voice and the other one with a low-pitch voice.
- Tay-Sachs disease is an inherited disorder as a result of incomplete inheritance where the body creates only half of the needed antibodies, where as a result, a person can be prone to diseases and cause accumulation of the lipids in the brain, causing the destruction of the nervous system and death in children.
- Sickle cell disease is an example of an incomplete dominance where the person will have half of the total hemoglobin normal and functioning, and the other half with abnormalities causing anemia and low oxygen levels.
- Parents, where the one has big hands, and the other has small hands will have a child who has a medium size hands.
Animal And Plant Examples
- A dog with a long tail and a short tail will have a puppy with a medium length tail.
- A blue bird and a red bird will have a multicolor nestling.
- A cat with dots and the one without them will have a kitten with a few dots on its body.
- A black sheep and a white sheep will have a gray sheep descendant.
- A snapdragon flower which is red crossed with a white one will have a pink color flower.
- A tall horse combined with a short one will have a medium height offspring.
- Rabbits with a white and red alleles will create a brown fur rabbit.
- Cat with a brown fur combined with a white cat will result in orange fur cat.