Mendel's Law, also known as the Law of Segregation, states that paired inherited units (genes) that control a character separate during germ cell formation (meiosis) so that each gamete (sperm or egg) receives only one member of each pair.
Understanding Mendel's Law of Segregation
This fundamental principle of genetics explains how traits are passed down from parents to offspring. Here's a breakdown:
- Paired Genes: Organisms inherit two copies of each gene, one from each parent. These gene pairs control specific traits, such as height or seed color.
- Segregation During Gamete Formation: During meiosis, the process of creating sperm or egg cells (gametes), these paired genes separate. This separation ensures that each gamete carries only one copy of each gene.
- Random Fertilization: During fertilization, a sperm and egg cell fuse. Because each gamete carries only one copy of each gene, the resulting offspring inherits one copy from each parent, reforming the pair.
Example: Pea Plant Height
Let's consider pea plant height, a classic example used by Gregor Mendel. Suppose:
- "T" represents the dominant allele for tallness.
- "t" represents the recessive allele for shortness.
A plant with the genotype "Tt" is heterozygous for height. According to Mendel's Law of Segregation, during gamete formation, the "T" and "t" alleles will separate. This means that some gametes will carry the "T" allele, while others will carry the "t" allele. When this plant reproduces, the offspring will inherit either a "T" or a "t" allele from this parent, along with one allele from the other parent. This random combination of alleles determines the offspring's height.
Implications of Mendel's Law
Mendel's Law of Segregation is crucial for understanding:
- Genetic Variation: It explains how variation arises in populations, as different combinations of genes are possible in offspring.
- Predicting Inheritance: It provides a basis for predicting the probability of offspring inheriting specific traits.
- Genetic Counseling: It helps genetic counselors assess the risk of inheriting certain genetic disorders.
In essence, Mendel's Law of Segregation is the cornerstone of modern genetics, providing a clear and concise explanation of how genes are inherited.
