The situation in which one member of a pair of allelic genes express itself over the other member is called dominance. The allele which fails to express is termed recessive allele. Dominance: 1. Dominance allele it is able to express itself even in the presence of its recessive allele. 2. It does not require another similar allele to produce its effect on the phenotype. eg: Tt is tall 3. Dominant allele or factor can form complete polypeptide or enzyme for expressing its effects eg: red colour of flower in pea. Recessive: 1. Recessive allele or factor is unable to express its effect in the presence of dominant allele. 2. It produces allele its phenotypic effect only in the presence of similar allele, e.g., tt is dwarf. 3. The recessive allele forms an incomplete or defective polypeptide or enzyme so that the expression consists of absence of the effect of dominant allele, eg: white flower colour in pea.?

Dominant and recessive are the two types of genes. The main difference between dominant and recessive is, dominant gene is expresses completely in the phenotype while recessive gene is not completely expresses in the phenotype.

Difference between Dominance and Recessiveness

Dominance and recessiveness are terms used in genetics to describe the inheritance patterns of traits. These concepts play a crucial role in understanding how genetic traits are passed down from one generation to the next. Let's delve into the details of each:

Dominance:
Dominance refers to the phenomenon where one allele of a gene masks or suppresses the expression of another allele in a heterozygous individual. In simpler terms, it means that one version of a gene (allele) is more influential in determining the physical or phenotypic trait than the other allele.

Key points about dominance include:

1. Dominant alleles are represented by uppercase letters (e.g., T).
2. Dominant traits are observable or expressed in individuals carrying one or two copies of the dominant allele.
3. When a dominant allele is present, it will always be expressed, regardless of the presence of a recessive allele.
4. Dominance is not an indicator of the frequency of an allele in a population.
5. Dominant traits do not necessarily confer an advantage or superiority over recessive traits.

Recessiveness:
Recessiveness is the opposite of dominance. It refers to the situation where an allele is only expressed in the absence of a dominant allele. In other words, for a recessive trait to be observed, an individual must have two copies of the recessive allele.

Key points about recessiveness include:

1. Recessive alleles are represented by lowercase letters (e.g., t).
2. Recessive traits are only observable or expressed in individuals carrying two copies of the recessive allele.
3. If a dominant allele is present, it will mask the expression of the recessive allele.
4. Recessive traits may seem less common in a population because individuals can carry the recessive allele without expressing the trait.
5. Recessive traits can be passed on to future generations if both parents carry at least one copy of the recessive allele, even if they do not express the trait themselves.

Examples:
To better understand the difference between dominance and recessiveness, let's consider an example using eye color:

- Dominant allele (B): Brown eye color
- Recessive allele (b): Blue eye color

If an individual has the genotype BB or Bb, they will have brown eyes because the dominant allele (B) suppresses the expression of the recessive allele (b). However, individuals with the genotype bb will have blue eyes because they have two copies of the recessive allele, and there is no dominant allele to mask its expression.

Conclusion:
In summary, dominance and recessiveness describe how different alleles of a gene interact and influence the expression of traits. Dominant alleles are always expressed, regardless of the presence of a recessive allele, whereas recessive alleles are only expressed when two copies are present and no dominant allele is present. Understanding the concepts of dominance and recessiveness is fundamental in comprehending the inheritance patterns of genetic traits.