Part A: Sutton and Boveri Hypothesis
Introduction
The Sutton and Boveri hypothesis is a foundational concept in genetics that connects the behavior of chromosomes with Mendel’s laws of inheritance. It laid the groundwork for the chromosome theory of inheritance.
Key Points of the Hypothesis
- Proposed independently by Walter Sutton (1902) and Theodor Boveri (1902).
- Suggested that genes are located on chromosomes.
- Chromosomes occur in pairs in diploid cells—just like Mendel’s factors (alleles).
- During meiosis, chromosomes segregate and independently assort, which aligns with Mendel’s laws of segregation and independent assortment.
Significance
- Provided cytological proof for Mendel’s laws.
- Led to the development of modern genetics by linking gene behavior with chromosomal movements during cell division.
Part B: Comment on Lethal Allele Gene Function
What Are Lethal Alleles?
Lethal alleles are gene mutations that cause the death of an organism when present in certain genotypic combinations. They interfere with essential biological functions required for survival.
Types of Lethal Alleles
- Recessive lethal alleles: Cause death only when present in homozygous form (e.g., aa). Example: Tay-Sachs disease in humans.
- Dominant lethal alleles: Cause death even in heterozygous form (Aa). Example: Huntington’s disease.
Effects
- Alters Mendelian ratios. For example, instead of a 3:1 ratio, a cross involving a recessive lethal may show a 2:1 phenotypic ratio because one genotype is missing due to death.
- Can occur early in embryonic development or later in life.
Importance in Genetics
- Help scientists understand gene function and development.
- Useful in genetic research and studying hereditary diseases.
Conclusion
The Sutton and Boveri hypothesis successfully bridged the gap between cytology and genetics by connecting chromosomes with Mendelian inheritance. Lethal alleles, on the other hand, highlight the critical role of gene function in survival and help explain deviations from classical Mendelian ratios.