dominant traits definition
Answers
Answer:
dominant trait is opposed to a recessive trait which is expressed only when two copies of the gene are present.
Answer:
Explanation:
Dominant: A genetic trait is considered dominant if it is expressed in a person who has only one copy of that gene. ... A dominant trait is opposed to a recessive trait which is expressed only when two copies of the gene are present.
A dominant trait is an inherited characteristic that appears in an offspring if it is contributed from a parent through a dominant allele. Traits, also known as phenotypes, may include features such as eye color, hair color, immunity or susceptibility to certain diseases and facial features such as dimples and freckles.
In sexually reproducing species, each individual has two pairs of chromosomes; humans have 23 pairs of chromosomes, and so 46 chromosomes in total. The chromosomes contain thousands of genes which code for the proteins that express and control all of the biochemical and physical features of an organism; this set of genes is an organism’s genotype.
Using a punnet square, it is possible to see how the 3:1 color ratio was achieved in the second generation:
Punnett square mendel flowers
Mendel furthered his research by studying other characteristics of peas, such as pod color (yellow or green), pea shape (round or wrinkled), flower position (axial or terminal) and height of the plants (tall or short); for each, the same outcome was seen as for flower color.
Using these basic principles of inheritance, it is possible to predict the percentage of different dominant traits expressed in the offspring, in a wide range of reproductive events. However, most traits within a phenotype of a complex organism are controlled by a number of different genes, so the reality is not always as simple as in Mendel’s experiments.
Examples of Dominant Traits
Human Dominant Traits
There are many characteristics of the human phenotype, which are controlled by dominant alleles:
Dark hair is dominant over blonde or red hair.
Curly hair is dominant over straight hair.
Baldness is a dominant trait.
Having a widow’s peak (a V-shaped hairline) is dominant over having a straight hairline.
Freckles, cleft chin and dimples are all examples of a dominant trait.
Having almond-shaped eyes is a dominant trait whereas having round eyes is a feature controlled by recessive alleles.
The trait of detached earlobes, as opposed to attached earlobes, is dominant.
Right-handedness is dominant over left-handedness.
The ability to roll the tongue is dominant over the inability to do so.
Astigmatism is dominant over normal vision.
The presence of webbed fingers is a dominant trait.
The development of 6 fingers instead of 5 is controlled by dominant alleles.
Brown eyes are dominant over blue eyes (however, eye color is controlled by more than one gene and is thus a polygenetic trait and cannot be explained by Mendelian genetics. People with green and hazel eyes have a mix of alleles for brown and blue eyes).
Other traits, which are not physically visible, are also controlled by dominant alleles, for example:
Immunity to poison ivy is controlled by a dominant allele.
High blood pressure is a dominant trait.
A & B blood types are dominant over the O blood type.
Susceptibility to migraines is a dominant trait.
Tone deafness is dominant over normal hearing.
It is important to note that dominant alleles are not better than recessive alleles; dominant traits can cause serious health problems for individuals (such as high blood pressure). Dominant traits are also not necessarily more common than recessive traits; although, if they have an effect on the health of individuals within a population, they may become more or less common in the gene pool over time, due to natural selection.
Dominant Traits for Selective Breeding
Just like in Mendel’s experiments, humans have been using genetics for selective breeding in animals, as well as fruit and vegetables, for thousands of years.
Dominant traits that are favorable, such as white wool in sheep, smooth coats in horses, and short legs in dachshunds, can be increased in a population by breeding individuals who have the dominant alleles. By consistently breeding individuals with the desired dominant trait, the dominant allele becomes more common in the population.
However, selective breeding does have downsides. When efforts are made to breed from a small founding population which is homozygous for the desired dominant trait, variation within the gene pool is low. Recessive genes that may cause health problems increase in frequency within the population, and are expressed when they end up homozygous. This is known as inbreeding, and can cause issues such as increased rate of cancers, heart disease and vision or hearing disorders.