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Understanding Genetic Variation - Exploring the Role of DNA and Proteins in Evolution

Delve into the intricate world of genetic variation, DNA coding for proteins, gene expression, mutations, and their impact on evolution. Learn about chromosome organization, ribosomes, and the flexible regulation of gene expression. Explore how genetic and environmental factors influence phenotypic traits, from simple polymorphisms to quantitative traits. Uncover insights into genotype-phenotype relationships, meiosis, and the fascinating interplay between genes and the environment.

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Understanding Genetic Variation - Exploring the Role of DNA and Proteins in Evolution

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  1. Chapter 5Raw material: heritable variation among individuals

  2. Proteins are chains of amino acids

  3. DNA codes for protein Mutation: any change to the genomic sequence

  4. Eukaryotic DNA is organized into chromosomes

  5. Chromosomes come in homologous pairs

  6. Ploidy can vary Ploidy: Number of copies of unique chromosomes in a cell

  7. Production of protein from DNA requires transcription and translation Gene expression: process by which information from a gene is transformed into product

  8. Ribosomes translate mRNA into protein

  9. Gene expression can be regulated in a number of ways

  10. RNA splicing can create multiple proteins from a single gene

  11. Regulation of gene expression is flexible

  12. Non-coding regions make up most of the genome • Non-coding regions include: • RNA genes • Pseudogenes • Mobile genetic elements

  13. microRNA can affect phenotypes

  14. Variation in genome size and complexity Most variation in size due to differences in mobile genetic elements

  15. Key Concepts • Most proteins function in four ways: • Enzymes • Cell-cell signaling • Receptors • Structural elements • Mutations are the raw material for evolution • In diploid organisms, deleterious mutations may be masked by a functional gene copy

  16. Key Concepts • All cells use mRNA to carry genetic information • Some viruses use RNA instead of DNA for the genome • Non-coding RNA plays critical roles in gene regulation

  17. Types of mutation

  18. Different types of mutation can alter the phenotype

  19. Examples of point mutations

  20. Germ line mutations are heritable • Somatic mutations: affect cells in the body of an organism; not heritable • Germ-line mutations: affect gametes; heritable and relevant to evolution

  21. Key Concepts • Changes in coding sequences and gene expression are heritable • Gene expression changes can affect when, where, and how much a gene is expressed

  22. Recombination generates variation

  23. Independent assortment ensures novel combinations of alleles

  24. Key Concepts • Meiosis generates considerable genetic variation • Recombination • Independent assortment

  25. Linking genotype and phenotype • Genotype: the genetic make-up of an individual • Phenotype: an observable measurable characteristic of an organism

  26. Simple polymorphisms can produce differences in phenotype

  27. Sometimes a single genotype can produce multiple phenotypes Polyphenic trait: single genotype produces multiple phenotypes depending on environment

  28. Quantitative traits influenced by genes and the environment Quantitative traits influenced by multiple genes; generate a normal distribution Francis Galton (1822-1911)

  29. Human height has genetic component

  30. QTL analysis can help discover genes influencing quantitative traits

  31. Key Concepts • Polyphenisms often result from a developmental threshold mechanism • Continuously varying traits are called quantitative traits • Evolutionary biologists study variation in the expression of phenotypic traits • Caused by genetic and environmental factors

  32. Environmental influences on gene expression • Phenotypic plasticity: changes in phenotype produced by a single genotype in different environments • Tailors organism to environment

  33. Key Concept • Gene expression often influenced by signals from the environment • Allows match to environmental circumstances

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