Alleles

An allele is a variant form of a gene. Genes are the units of heredity, and they are made up of DNA. Alleles can come in different forms and may lead to different observable traits, known as phenotypes. For example, the gene for eye color may have alleles for blue eyes, brown eyes, or green eyes.

Mendelian Genetics

One of the foundational principles of genetics is Mendel's law of segregation. This law states that during the formation of gametes (sperm and egg cells), the two alleles for a gene separate so that each gamete carries only one allele for each gene. This is the basis for inheritance of traits from parents to offspring.

Types of Alleles

There are different types of alleles, including:

Dominant Alleles: These alleles are expressed as a visible trait even when only one copy is present.
Recessive Alleles: These alleles are only expressed when two copies are present, and their effects are masked by dominant alleles.
Codominant Alleles: In some cases, both alleles in a heterozygous individual are fully expressed, resulting in a phenotype that is a combination of both alleles.
Multiple Alleles: Some genes may have more than two allele forms. For example, the ABO blood group system in humans has three alleles: A, B, and O.

Genotype and Phenotype

The combination of alleles an individual possesses is known as their genotype. The observable physical and biochemical traits that result from the interaction of an organism's genotype with the environment are called the phenotype.

Genetic Crosses

Understanding alleles is crucial in genetic crosses, where the possible combinations of alleles from two parents are considered to predict the traits of their offspring. Punnett squares and probability calculations are often used to analyze genetic crosses.

Applications in Medicine and Agriculture

Knowledge of alleles and their inheritance patterns is essential in fields such as medicine, where understanding genetic diseases and traits is important for diagnosis and treatment. In agriculture, breeding practices rely on the principles of allele inheritance to develop crops and livestock with desired traits.

◂Chemistry Worksheets and Study Guides High School. The Science of Chemistry

Worksheet/Answer key

The Science of Chemistry

Worksheet/Answer key

The Science of Chemistry

Worksheet/Answer key

The Science of Chemistry

The resources above cover the following skills:

Nature of Science

The Practice of Science - A: Scientific inquiry is a multifaceted activity; The processes of science include the formulation of scientifically investigable questions, construction of investigations into those questions, the collection of appropriate data, the evaluation of the meaning of those data, and the communication of this evaluation. B: The processes of science frequently do not correspond to the traditional portrayal of ''the scientific method.'' C: Scientific argumentation is a necessary part of scientific inquiry and plays an important role in the generation and validation of scientific knowledge. D: Scientific knowledge is based on observation and inference; it is important to recognize that these are very different things. Not only does science require creativity in its methods and processes, but also in its questions and explanations.

Define a problem based on a specific body of knowledge, for example: biology, chemistry, physics, and earth/space science, and do the following:

Use tools to gather, analyze, and interpret data (this includes the use of measurement in metric and other systems, and also the generation and interpretation of graphical representations of data, including data tables and graphs)

Alleles

Mendelian Genetics

Types of Alleles

Genotype and Phenotype

Genetic Crosses

Applications in Medicine and Agriculture

Further Reading

◂Chemistry Worksheets and Study Guides High School. The Science of Chemistry

The resources above cover the following skills: