Lecture 6: Genetic Evolution & Duplication Flashcards
Genome Size Variation
Genome Size (Haploid Genome Size): Not directly correlated with complexity. For example, some amphibians have much more DNA than other animals, yet similar levels of complexity.
Gene Structure and Regulation
1) Gene Anatomy: Genes have regulatory elements, such as enhancers and promoters, alongside exons and introns.
2) Gene Regulatory Networks (GRNs): Most genes operate within networks, influenced by transcription factors and promoter binding.
Gene Duplication Mechanisms
1) Unequal Crossing Over: Duplicates portions or entire genes.
2) Retroposition: Produces duplicate genes lacking regulatory elements, often leading to pseudogenes.
3) Genome Duplication: Duplicates the entire genome or chromosome, preserving regulatory elements.
4) Segmental Duplication: Partial duplications with currently unknown mechanisms.
Pseudogenes
Non-functional Genes: Often arise from mutations or incomplete duplications.
Examples: Humans have many pseudogenes, including ~60% of olfactory receptor genes.
Outcomes of Gene Duplication
1) Redundancy: Duplicate genes can become redundant unless advantageous (e.g., increased rRNA).
2) Subfunctionalization: Duplicated genes evolve slightly different functions.
3) Neofunctionalization: Rarely, duplicates develop new functions entirely, such as specialized opsins for color vision.
Examples of Gene Duplication
1) Colobine Monkeys: Duplicated RNASE1B specializes in digesting bacterial RNA.
2) Hemoglobin Genes: Gene duplications result in functional diversity (e.g., fetal vs. adult hemoglobin).
3) Hox Genes: Control body plans, timing, and spatial development in organisms.
Summarize what was discussed in this lecture, the key concepts and ideas!
1) Gene Duplication: The primary source of new genes, allowing functional diversification.
2) Redundancy and New Functions: While many duplicated genes remain similar to their parental genes, others develop new roles through subfunctionalization or neofunctionalization.
3) Modularity in Evolution: Gene duplication underpins evolutionary modules, such as the evolution of hemoglobin and Hox genes, shaping organism complexity.
What is the evolutionary impact of Gene Duplication?
1) Microevolution vs. Macroevolution: Small mutations contribute to microevolution, while gene duplications drive significant changes in gene regulation or function (macroevolution).
2) Syntax Evolution Model: Suggests gene duplication is essential for generating new genes and modular functions, driving both phenotypic and genotypic evolution.
