In an 1889 book titled Natural Inheritance (Macmillan, New York), Francis Galton, who investigated the inheritance of measurable (quantitative) traits, formulated a law of 'ancestral inheritance.' The law stated that individuals inherit approximately one-half of their genetic traits from each parent, about one-quarter of the traits from each grandparent, one-eighth from each great grandparent, and so on. In light of the chromosome theory of heredity, argue either in favor of Galton's law or against it.

Verified step by step guidance

1. <span>Step 1: Understand Galton's Law of Ancestral Inheritance</span> - Galton's law suggests that genetic traits are inherited in diminishing proportions from ancestors, with each generation contributing half as much as the previous one. This implies a geometric progression in the contribution of genetic material from ancestors.
2. <span>Step 2: Consider the Chromosome Theory of Heredity</span> - The chromosome theory of heredity, developed in the early 20th century, posits that genes are located on chromosomes, which are the vehicles of genetic inheritance. Each parent contributes one set of chromosomes to the offspring, leading to a 50% genetic contribution from each parent.
3. <span>Step 3: Analyze the Contribution of Grandparents and Beyond</span> - According to the chromosome theory, while each parent contributes 50% of the genetic material, the contribution from grandparents and further ancestors is not directly halved in the same manner as Galton's law suggests. Instead, the genetic contribution is a result of recombination and independent assortment during meiosis.
4. <span>Step 4: Evaluate the Role of Recombination</span> - Recombination during meiosis leads to new combinations of alleles, which means that the genetic contribution from ancestors is not a simple halving process. This process can result in some alleles being passed on more frequently than others, depending on linkage and other factors.
5. <span>Step 5: Conclude with a Critical Perspective</span> - While Galton's law provides an intuitive understanding of diminishing genetic influence from distant ancestors, it oversimplifies the complex mechanisms of genetic inheritance as explained by the chromosome theory. The actual genetic contribution from ancestors is influenced by recombination, linkage, and other genetic phenomena, making it more complex than a simple geometric progression.>

Key Concepts

Chromosome Theory of Heredity

The chromosome theory of heredity posits that genes are located on chromosomes, which are passed from parents to offspring during reproduction. This theory explains how traits are inherited through the segregation and independent assortment of chromosomes during meiosis. It provides a genetic basis for understanding inheritance patterns, contrasting with Galton's more simplistic view of trait inheritance.

Quantitative Traits

Quantitative traits are characteristics that are influenced by multiple genes and can be measured on a continuous scale, such as height or weight. These traits often exhibit a normal distribution in a population and are affected by both genetic and environmental factors. Understanding quantitative traits is essential for evaluating Galton's law, as it highlights the complexity of inheritance beyond simple Mendelian ratios.

Ancestral Inheritance

Ancestral inheritance refers to the idea that traits are passed down from ancestors in a predictable manner, as proposed by Galton. His law suggests a geometric distribution of genetic contribution from ancestors, which simplifies the complexities of genetic inheritance. However, this concept may not fully account for the random assortment of alleles and the influence of multiple genes on traits, challenging its validity in light of modern genetics.