Slide 1: Genetics and Evolution - Molecular Basis of Inheritance

  • Introduction to genetics and evolution
  • Importance of understanding molecular basis of inheritance
  • Overview of initiation of mRNA binding to tRNA
  • Genetic variation and its role in evolution
  • Topics to be covered in this lecture

Slide 2: DNA and RNA Structure

  • DNA structure: double helix, nucleotides, base pairing (A-T, G-C)
  • RNA structure: single-stranded, nucleotides, base pairing (A-U, G-C)
  • Comparison of DNA and RNA structure

Slide 3: Central Dogma of Molecular Biology

  • Overview of the central dogma
  • DNA replication: process and significance
  • Transcription: synthesis of mRNA from DNA template
  • Translation: synthesis of protein using mRNA template
  • Importance of the central dogma in understanding inheritance

Slide 4: Transcription

  • Role of RNA polymerase in transcription
  • Initiation, elongation, and termination of transcription
  • Promoters and transcription factors
  • Examples of how gene expression is regulated through transcription

Slide 5: Genetic Code

  • Introduction to the genetic code
  • Codons and their role in protein synthesis
  • Start codon (AUG) and stop codons (UAA, UAG, UGA)
  • Examples of how genetic code is used to decode mRNA sequences

Slide 6: Translation

  • Role of ribosomes in translation
  • Initiation, elongation, and termination of translation
  • tRNA and its role as the interpreter between mRNA and amino acids
  • Examples of how amino acids are added to the growing peptide chain

Slide 7: Initiation of Translation

  • Initiator tRNA and its binding to the mRNA
  • Base pairing between the codon and anticodon
  • Ribosome binding site (RBS) and start codon recognition
  • Examples of how initiation of translation is regulated

Slide 8: Elongation of Translation

  • A-site, P-site, and E-site on the ribosome
  • Codon recognition and peptide bond formation
  • Movement of tRNA from A-site to P-site to E-site
  • Examples of how elongation of translation is regulated

Slide 9: Termination of Translation

  • Stop codon recognition by release factors
  • Release of the completed protein from the ribosome
  • Role of termination codons in protein synthesis
  • Examples of how termination of translation is regulated

Slide 10: Genetic Variation and Evolution

  • Introduction to genetic variation
  • Importance of genetic variation in evolution
  • Types of genetic variation: mutations, recombination, and gene flow
  • Examples of how genetic variation contributes to the evolution of populations
  1. Genetics and Evolution- Molecular Basis of Inheritance
  • Initiator tRNA binds to the mRNA through base pairing between the codon and anticodon
  • The ribosome binding site (RBS) and start codon recognition are crucial for the initiation of translation
  • Examples: AUG is the start codon that initiates translation in most organisms
  • The initiation of translation is tightly regulated to control gene expression and protein synthesis
  • Dysregulation of the initiation process can lead to various diseases
  1. Elongation of Translation
  • During elongation, the growing peptide chain is extended by adding amino acids
  • The A-site, P-site, and E-site on the ribosome play specific roles in the process
  • Codon recognition occurs in the A-site, and peptide bond formation happens in the P-site
  • Examples: Eukaryotic elongation factors EF1 and EF2 aid in the process of elongation
  • Dysregulation of elongation can lead to errors in protein synthesis and can affect cellular function
  1. Termination of Translation
  • Termination occurs when a stop codon is recognized on the mRNA by release factors
  • The release of the completed protein from the ribosome marks the end of translation
  • Termination codons, such as UAA, UAG, and UGA, signal the ribosome to stop protein synthesis
  • Examples: Release factors RF1, RF2, and RF3 are involved in the termination process
  • Dysregulation of termination can lead to incomplete or abnormal proteins and can impact cellular function
  1. Regulation of Translation
  • Translation can be regulated at multiple steps to control gene expression
  • Factors such as availability of initiation factors and regulatory proteins influence translation rates
  • Examples: Translational repressors and activators can bind to mRNA and inhibit or enhance translation
  • Alterations in translation regulation can lead to abnormal protein synthesis and contribute to diseases
  • Understanding the mechanisms of translation regulation is crucial for developing targeted therapies
  1. Genetic Variation and Evolution
  • Genetic variation is the diversity in DNA sequences within a population or species
  • Genetic variation plays a crucial role in evolution by providing raw material for natural selection
  • Examples: Mutations introduce new genetic variations, and recombination shuffles existing variations
  • Gene flow between populations can also introduce new genetic variations
  • Genetic variation contributes to the adaptation of organisms to changing environments
  1. Types of Genetic Variation
  • Mutations: Changes in the DNA sequence due to various factors like errors in replication or exposure to mutagens
  • Recombination: Exchange of genetic material between homologous chromosomes during meiosis
  • Gene Flow: Transfer of genetic information from one population to another through migration or interbreeding
  • Examples: Point mutations, insertions, deletions, and chromosomal rearrangements are types of genetic variations
  • Genetic variations can be neutral, beneficial, or deleterious, influencing evolution
  1. Role of Genetic Variation in Evolution
  • Genetic variations provide the variation necessary for natural selection to act upon
  • Beneficial variations increase an organism’s fitness, leading to their increased survival and reproduction
  • Examples: Antibiotic resistance in bacteria and insecticide resistance in insects are the result of beneficial variations
  • Deleterious variations may decrease an organism’s fitness and are selected against
  • Genetic variation is the basis for adaptations and the diversity of life on Earth
  1. Hardy-Weinberg Equilibrium
  • The Hardy-Weinberg equilibrium principle describes a population’s genetic equilibrium
  • It states that the frequency of alleles and genotypes in a population remains constant over generations
  • The equation p^2 + 2pq + q^2 = 1 represents allele frequencies, where p and q are the frequencies of two alleles
  • Examples: The Hardy-Weinberg equilibrium helps researchers estimate allele frequencies and detect deviations from equilibrium
  • Factors like mutation, genetic drift, migration, and natural selection can disrupt the equilibrium
  1. Mechanisms of Natural Selection
  • Natural selection is the process by which advantageous traits become more common in a population
  • Types of natural selection include directional, stabilizing, and disruptive selection
  • Examples: An increase in antibiotic-resistant bacteria is an outcome of directional selection
  • Stabilizing selection favors intermediate phenotypes, ensuring the preservation of well-adapted traits
  • Disruptive selection promotes the survival of extreme phenotypes, leading to divergence
  1. Speciation and Divergence
  • Speciation is the process by which new species arise from existing ones
  • Isolation, genetic divergence, and reproductive isolation are key factors in speciation
  • Examples: Allopatric speciation occurs when populations are physically separated, such as by geographical barriers
  • Sympatric speciation occurs without physical separation, often due to genetic or ecological factors
  • Speciation plays a significant role in biodiversity and the shaping of Earth’s ecosystems.
  1. Genetics and Evolution- Molecular Basis of Inheritance - Intiator tRNA binds to the mRNA through base pairing between the codon and anticodon
  • The binding of initiator tRNA to mRNA is facilitated by complementary base pairing between the codon on mRNA and the anticodon on tRNA.
  • This ensures the correct amino acid is added to the growing polypeptide chain.
  • The binding is stabilized by hydrogen bonding between the bases.
  • Examples: AUG codon on mRNA pairs with UAC anticodon on initiator tRNA in eukaryotes.
  • Dysregulation of this binding can lead to errors in translation and protein synthesis.
  1. Elongation of Translation
  • During elongation, additional amino acids are added to the growing polypeptide chain.
  • The next tRNA molecule carrying the corresponding amino acid enters the ribosome.
  • Peptide bond formation occurs between the amino acids.
  • The ribosome translocates, moving the mRNA and tRNA by one codon.
  • Examples: Peptidyl transferase catalyzes the formation of peptide bonds during elongation.
  • Dysregulation of elongation can lead to incomplete proteins or elongated polypeptide chains.
  1. Termination of Translation
  • Termination signals the end of protein synthesis.
  • An mRNA stop codon is recognized by release factors.
  • The release factors catalyze the hydrolysis of the bond between the completed polypeptide chain and the tRNA.
  • The completed protein is released from the ribosome.
  • Examples: Release factors RF1, RF2, and RF3 are involved in the termination process.
  • Dysregulation of termination can result in premature termination or production of aberrant proteins.
  1. Regulation of Translation
  • Translation can be regulated to control gene expression and protein synthesis.
  • Regulatory proteins can bind to mRNA and influence translation rates.
  • The availability of initiation factors affects the initiation of translation.
  • Examples: Translational repressors inhibit the translation of specific mRNAs.
  • Translational activators enhance translation by promoting initiation.
  • Dysregulation of translation regulation can lead to an imbalance in protein synthesis and dysfunction.
  1. Regulation of Gene Expression through Translation
  • Translation plays a vital role in regulating gene expression.
  • Translational control can influence protein abundance without affecting mRNA levels.
  • Examples: Translational repression of specific mRNAs can occur during development or in response to environmental stimuli.
  • Translational activation can be mediated by specific signaling pathways or stimuli, leading to increased protein synthesis.
  • Dysregulation of translational control mechanisms can contribute to various diseases.
  1. Genetic Variation and Evolution
  • Genetic variation is the diversity in gene sequences within a population.
  • Genetic variation acts as the raw material for natural selection and drives evolution.
  • Examples: Single nucleotide polymorphisms (SNPs), insertions, deletions, and chromosomal rearrangements are sources of genetic variation.
  • Genetic variation can arise from mutations, recombination, and gene flow.
  • Genetic variation provides the basis for adaptation to changing environments.
  1. Mutations and Genetic Variation
  • Mutations are changes in DNA sequence that can introduce genetic variation.
  • Mutations can be spontaneous or induced by environmental factors.
  • Different types of mutations include point mutations, insertions, deletions, and chromosomal rearrangements.
  • Examples: Sickle cell anemia is caused by a point mutation in the gene encoding hemoglobin.
  • Mutations can be neutral, beneficial, or deleterious, influencing the survival and adaptation of organisms.
  1. Recombination and Genetic Variation
  • Recombination is the exchange of genetic material between homologous chromosomes.
  • It occurs during meiosis and contributes to genetic variation.
  • Crossing over between chromatids leads to the shuffling of genetic information.
  • Examples: Independent assortment and crossing over during meiosis introduce new combinations of alleles.
  • Recombination increases genetic diversity, allowing populations to adapt to changing environments.
  1. Gene Flow and Genetic Variation
  • Gene flow is the transfer of genetic information between populations.
  • It occurs through migration and interbreeding.
  • Gene flow can introduce new genetic variations to populations.
  • Examples: Immigration and emigration of individuals can lead to the movement of alleles between populations.
  • Gene flow can homogenize populations or introduce novel variations, depending on the gene flow rate.
  1. Importance of Genetic Variation in Evolution
  • Genetic variation is crucial for evolution and the adaptation of organisms.
  • Natural selection acts on genetic variation, favoring traits that increase fitness.
  • Examples: Peppered moth evolution due to industrial melanism.
  • Genetic variation allows for the survival of populations in changing environments.
  • Understanding genetic variation helps in studying the evolutionary history of organisms.