Here's a breakdown of lethal mutations:

* Impact: They disrupt essential biological processes, leading to the death of the organism.

* Timing: They can be embryonic lethal, meaning they cause death before birth, or post-natal lethal, meaning they cause death after birth.

* Types: Lethal mutations can be caused by:

* Single gene mutations: Affecting a single gene.

* Chromosomal mutations: Affecting a large section of a chromosome.

* Multi-factorial mutations: A combination of genetic and environmental factors.

Examples of Lethal Mutations:

* Cystic Fibrosis: A recessive genetic disorder that causes severe lung problems and other complications, often leading to premature death.

* Tay-Sachs Disease: A fatal genetic disorder that affects the nervous system, leading to progressive damage and death in early childhood.

* Huntington's Disease: A dominant genetic disorder that causes progressive neurodegeneration and eventually leads to death.

Important Notes:

* Not all mutations are lethal: Many mutations are harmless or have only minor effects.

* Evolutionary Impact: Lethal mutations are eliminated from the population over time, as individuals with these mutations do not survive to reproduce. This contributes to the natural selection process.

Let me know if you'd like to explore specific types of lethal mutations or their impact on evolution in more detail!