quickconverts.org
☰

Complete Dominance Vs Incomplete Dominance

Image related to complete-dominance-vs-incomplete-dominance

The Tale of Two Traits: Understanding Complete and Incomplete Dominance



Genetics, the science of heredity, often presents a simplified picture of inheritance. We're frequently taught about dominant and recessive alleles, where one allele completely masks the other. However, the reality is far more nuanced. While complete dominance is a fundamental concept, it's not the only story. Many traits don't follow this simple pattern, exhibiting instead a phenomenon called incomplete dominance. This article delves into the differences between complete and incomplete dominance, providing a clear understanding of these inheritance patterns and their implications. Understanding these distinctions is crucial for comprehending the complex interplay of genes and the diversity of traits we observe in the natural world, from flower colors to human diseases.


Complete Dominance: The Classic Case



In complete dominance, one allele completely masks the expression of another allele. This means that if an individual inherits even one copy of the dominant allele, the dominant trait will be expressed. The recessive allele is only expressed when an individual inherits two copies of it (homozygous recessive).

Consider the classic example of pea plant flower color, studied by Gregor Mendel. The allele for purple flowers (P) is dominant over the allele for white flowers (p). A plant with the genotype PP or Pp will have purple flowers, while a plant with the genotype pp will have white flowers. The purple allele (P) completely masks the expression of the white allele (p) in heterozygotes (Pp).

This simple dominance pattern is observed in many other traits, including human traits like the presence of a widow's peak (dominant) versus a straight hairline (recessive), or the ability to roll one's tongue (dominant) versus the inability to do so (recessive). In each instance, the dominant allele completely overshadows the recessive allele's effect.


Incomplete Dominance: A Blend of Traits



Incomplete dominance, on the other hand, presents a more subtle picture. In incomplete dominance, neither allele is completely dominant over the other. Instead, the heterozygote displays an intermediate phenotype, a blend of the two homozygous phenotypes.

A classic example is the snapdragon flower. The allele for red flowers (R) and the allele for white flowers (W) exhibit incomplete dominance. A plant homozygous for red (RR) will have red flowers, and a plant homozygous for white (WW) will have white flowers. However, a heterozygous plant (RW) will exhibit pink flowers. The red and white pigments are blended, resulting in a new phenotype.

This blending isn't always a simple arithmetic mean; the exact shade of pink might vary depending on the specific genes involved and environmental factors. The key is that the heterozygote creates a phenotype distinct from either homozygote, indicating neither allele fully suppresses the other.


Distinguishing Complete and Incomplete Dominance: A Practical Approach



The key difference lies in the phenotype of the heterozygote. In complete dominance, the heterozygote expresses the same phenotype as the homozygous dominant individual. In incomplete dominance, the heterozygote exhibits a unique phenotype intermediate between the two homozygotes.

Consider a simple Punnett square. With complete dominance, a cross between a homozygous dominant (e.g., PP) and a homozygous recessive (e.g., pp) individual will produce offspring with only the dominant phenotype (Pp – all purple flowers). However, in incomplete dominance, the same cross (e.g., RR x WW) will produce offspring with a distinct intermediate phenotype (RW – all pink flowers). This difference in the F1 generation is crucial for distinguishing between the two patterns of inheritance.


Real-World Implications and Examples



Beyond flowers, incomplete dominance plays a role in various biological processes:

Human traits: Certain human traits show incomplete dominance. For example, the inheritance of Tay-Sachs disease involves incomplete dominance at the biochemical level. Individuals homozygous for the disease allele exhibit severe symptoms, while heterozygotes have a less severe form of the disease.
Coat color in animals: Many animals exhibit incomplete dominance in coat color. For instance, some breeds of horses display incomplete dominance in coat color, where a cross between a chestnut horse (RR) and a cremello horse (WW) results in a palomino horse (RW) with an intermediate coat color.
Plant height: In some plants, the height can be determined by alleles exhibiting incomplete dominance, resulting in a range of plant heights depending on the genotype.


Conclusion



Complete and incomplete dominance represent distinct patterns of inheritance, both fundamental to understanding the expression of genes and the diversity of traits observed in the biological world. Complete dominance entails one allele fully masking another, while incomplete dominance leads to a blended phenotype in heterozygotes. Recognizing these patterns is critical for genetic analysis, predicting offspring phenotypes, and understanding the complex interplay of genes and their environment.


Frequently Asked Questions (FAQs)



1. Can environmental factors influence the expression of incomplete dominance? Yes, environmental factors can modify the expression of incomplete dominance. For example, temperature can influence the intensity of pigment expression in some plants exhibiting incomplete dominance.

2. Are there inheritance patterns beyond complete and incomplete dominance? Yes, codominance is another important pattern where both alleles are expressed equally in the heterozygote (e.g., AB blood type). There are also cases of multiple alleles and polygenic inheritance, further complicating the picture.

3. How can I determine if a trait shows complete or incomplete dominance? By analyzing the phenotypes of the offspring from crosses, particularly the heterozygotes. If the heterozygote displays the same phenotype as one of the homozygotes, it's likely complete dominance. If the heterozygote shows an intermediate phenotype, it suggests incomplete dominance.

4. Is incomplete dominance always a simple blend of phenotypes? Not always. The intermediate phenotype might not be a precise arithmetic mean, and its exact appearance can be influenced by other genetic and environmental factors.

5. Can incomplete dominance be used in plant breeding? Yes, breeders can utilize incomplete dominance to create new varieties with desirable intermediate phenotypes. For example, breeders might cross two varieties of flowers to obtain a new color not found in either parent.

Links:

Converter Tool

Conversion Result:

=

Note: Conversion is based on the latest values and formulas.

Formatted Text:

221 cm in inches
213 grams in ounces
8000 km in miles
192 oz to liters
what is 135 kg in pounds
870g to lbs
50m to ft
145 lbs a kg
540 grams in pounds
2 000 ml to oz
450 g to lbs
25 ml to tbsp
102 cm to ft
122cm to in
3 to m

Search Results:

Genetics Punnett Squares And Incomplete Vs Codominance 2. Tackling Incomplete Dominance: Incomplete dominance occurs when neither allele is completely dominant over the other. The heterozygote displays an intermediate phenotype. A …

Incomplete Dominance and Codominance - Mrs. Moody In a species of birds, incomplete dominance for black (BB) and white (WW) feathers is observed. Heterozygotes (BW) are blue. If two blue birds are crossed, what will be the possible …

Science 10: omplete Dominance (Mendelian), odominance, and Incomplete ... Science 10: omplete Dominance (Mendelian), odominance, and Incomplete Dominance lass Notes Phenotypes Allele / Genotype Notation Example omplete Dominance 2 phenotypes: …

Punnett Problems 1: Complete Dominance and Incomplete Dominance In humans, normal vision is completely dominant (N) and myopia (nearsightedness) is recessive (n). A homozygous normal female marries a myopic male. What would be the genotypes and …

Co-Dominance, Incomplete Dominance, and Epistasis Worksheet … 3. Spotted flowers are an example of co-dominance. A red snapdragon flower (RR) is paired with a white snapdragon (WW). What will their offspring look like if both red and white are dominant …

Multiple Alleles and Incomplete Dominance note and worksheet Incomplete Dominance - There are many cases where two alleles are equally dominant, and one doesn’t “pull rank” over the other. In these cases, an entirely new phenotype is observed when …

complete dominance incomplete dominance codominance Incomplete dominance: if a red (RR) and white flower (rr) were bred, resulting in 100% heterozygous offspring (Rr), what phenotype would be seen according to the rules of …

Genetic Problems – CO-DOMINANCE & INCOMPLETE DOMINANCE Co-dominance is observed in tabby cats. A cross between a black cat and a tan cat produces a tabby pattern (black and tan fur together). a. Cross a black cat with a tabby cat. What are the …

CO-DOMINANCE/INCOMPLETE DOMINANCE – Worksheet #2 … Incomplete Dominance Problems . 1. In snapdragons, flower color is controlled by incomplete dominance. The two alleles are red (R) and white (w). The heterozygous genotype is …

Codominance Dominance & Incomplete - stosichscience.ca Incomplete Dominance - An allele that can’t totally block the recessive allele - One dominant allele isn’t enough to give the dominant trait - When homozygous dominant = full dominant trait - …

Incomplete and Codominance Worksheet Name - SCSD1 1. Explain the difference between incomplete dominance and codominance: 2. In some chickens, the gene for feather color is controlled by codiminance. The allele for black is B and the allele …

CODOMINANT/INCOMPLETE DOMINANCE PRACTICE … CODOMINANT/INCOMPLETE DOMINANCE PRACTICE WORKSHEET 1. Explain the difference between incomplete and codominance. Co-Dominance Problems 2. In a certain fish, blue …

Incomplete Dominance Worksheet - Biology This worksheet gives you practice in problems dealing with incomplete dominance. Below is a complete example for you to follow. Important information: With incomplete dominance R' is …

Incomplete Dominance and Codominance Worksheet In a species of birds, incomplete dominance between alleles for black (B) and white (W) feathers is observed. Heterozygotes are blue. If two blue birds are crossed, what will be the possible …

INCOMPLETE DOMINANCE VS CO-DOMINANCE - edscl.in Incomplete Dominance •Incomplete dominance is when a dominant allele, form of a gene, does not completely mask the effects of a recessive alleles, and the organism’s resulting physical …

Incomplete dominance and Codominance - Mr Sikkema's Course … Incomplete dominance [both traits blend - at molecular level] i. Eye colour (mixed not spotted)

Incomplete dominance and co-dominance - ekac.in Complete dominance, as inferred by Mendel, refers to the type of dominance in which one allele completely masks the expression of other allele and is therefore said to be completely dominant.

Punnett Squares: Codominance and Incomplete Dominance A species of flowers exhibits incomplete dominance between the allele for red flowers and the allele for white flowers. If a plant homozygous for red flowers is crossed with a plant that is …

Genetics: Punnett Squares and Incomplete vs Codominance In an individual with a heterozygous genotype, the dominant allele shows up in the offspring and the recessive allele gets covered up and doesn’t show; we call this complete dominance. …

100 Points Genetics: Punnett Squares Practice Packet: Ness … In an individual with a heterozygous genotype, the dominant allele shows up in the offspring and the recessive allele gets covered up and doesn’t show; we call this complete dominance. …