Genomics

Multi Omics Introduction

Institution: Munster Technological University
Course: BIOL8023
Instructor: Dr. Saravana Periaswamy
Website: www.mtu.ie

What is Genomics?

• Definition: Genomics is the study of an organism's genome, which encompasses all of its DNA, including both coding regions (genes) and non-coding regions (intergenic regions).

• Distinction from Genetics:

  • Genomics: Focuses on the complete set of genetic information (genome).

  • Genetics: The study of heredity and the function and composition of single genes.

• Key Concepts:

  • Genome: The complete genetic information of an organism.

  • Gene: A specific sequence of DNA that encodes a functional molecule.

What is DNA?

• Definition: DNA (Deoxyribonucleic Acid) is a molecule that contains biological instructions essential for development, survival, and reproduction of organisms.

• Transmission: DNA is passed from adult organisms to offspring during reproduction.

Location of DNA:

• Eukaryotes:

  • Found in the nucleus (chromosomal DNA) and mitochondria (mitochondrial DNA).

• Prokaryotes:

  • Found in the nucleoid (chromosomal DNA) and plasmids.

Structure of DNA

• Double Helix Components:

  • Composed of a backbone of phosphate groups and sugars, interlinked with nitrogen bases:

  • Bases:

    • Adenine (A) pairs with Thymine (T)

    • Guanine (G) pairs with Cytosine (C)

DNA Replication

• Definition: The process of producing two identical copies of DNA from one original DNA molecule (semi-conservative replication).

• Significance: Essential for cell growth and reproduction.

Process of DNA Replication:

1. Initiation:

   • The DNA double helix splits into two strands.

2. Template Function:

   • Each single strand serves as a template for building two new double-stranded DNA molecules.

3. Enzymatic Process:

   • Key Enzymes:

   • Helicase: Unwinds the parental double helix.

   • Primase: Adds a short primer to the template strand.

   • DNA Polymerase: Binds nucleotides to form new strands.

   • Exonuclease: Removes RNA primer and inserts correct bases.

   • Ligase: Joins Okazaki fragments and seals nicks in the sugar-phosphate backbone.

DNA Sequencing

• Description: Utilizes the principles of DNA replication to determine the sequence of nitrogen bases in a DNA molecule.

Applications of DNA Sequencing:

• Molecular Biology: Identifying genes or regulatory instructions.

• Cancer Screening: Detecting mutations that may cause diseases.

• Microbiology: Characterizing organisms that are difficult to isolate.

• Forensic Science: Identifying individuals.

• Agriculture: Screening seeds and livestock genetics.

Development of DNA Sequencing

• 1958: Francis Crick proposed that the nucleotide sequence determines the amino acid sequence of proteins.

• 1977: Frederick Sanger published a chain-terminating DNA sequencing method (Sanger sequencing).

  • Method by Chemical Degradation: Developed by Allan Maxam and Walter Gilbert.

Historical Milestones in DNA Sequencing:

• 1981: Human mitochondrial genome sequenced.

• 1990: Launch of the Human Genome Project.

• 2003: Completion announcement of the Human Genome Project.

Sanger Sequencing

• Chain Termination Method:

• Components Involved:

1. Template DNA: The original strand.

2. dNTPs: Contains 4 types of deoxynucleotides.

3. ddNTPs: Dideoxynucleotides, terminates chain growth.

• Procedure Stages:

1. Primer annealing and chain extension.

2. ddNTP addition stops chain extension.

3. Capillary gel electrophoresis separates DNA fragments.

4. Sequence analysis conducted post-detection.

Automated DNA Sequencing

• Description: Early methods were time-consuming; automation improved efficiency.

• First-generation sequencers:

  • 1987: First fully automated DNA sequencer (AB370A) developed.

  • 1995: The AB310 sequencer introduced capillary electrophoresis.

Next Generation Sequencing (NGS)

• Definition: Employs newer technologies allowing for faster and more efficient DNA sequencing.

• Key Systems:

  • 454 Sequencer: Pyrosequencing method.

  • Illumina: Sequencing by synthesis.

  • SOLiD: Sequencing by ligation.

• Advantages of NGS:

  • Higher accuracy and throughput with lower cost.

Third Generation Sequencing (TGS)

• Description: Eliminates the PCR amplification step, providing real-time DNA synthesis observations.

• Applications: Can generate longer reads and is useful for complicated genomes.

Human Genome Project

• Definition: International collaborative research initiative aimed at mapping and understanding human DNA.

• Timeline:

  • 1990: Initiation, involving $3 billion funding.

  • 2000: Rough draft completed.

  • 2003: Complete human genome sequence announced.

• Key Leaders: David Galas, James Watson, and later, Francis Collins.

Approach and Methodology of HGP:

• Hierarchical Shotgun Approach:

  • Initial mapping followed by sequencing.

  • Two Map Types Used:

  1. Genetic Map: Gene arrangements based on recombinant frequencies.

  2. Physical Map: Exact gene distances measured in base pairs.

Metagenomics

• Definition: Study of total genomic DNA from complex environmental samples, typically microbial populations.

• Approach: Culture-independent; allows for discovering novel species.

Study Approaches in Metagenomics:

1. Targeted Metagenomics: Sequences specific genomic regions (e.g., 16S rRNA).

2. Shotgun Metagenomics: Sequences all metagenomic DNA, identifying both the species and their functionalities.

Human Microbiome Project

• Objective: Characterization of human microbiota and its impacts on health and disease.

• Phases:

  • HMP1 (2008-2013): Focusing on healthy individuals.

  • iHMP (2014-2016): Investigates microbiomes associated with disease conditions.

Revision Topics

1. Definition and scope of Genomics.

2. Structure, function, and replication of DNA.

3. Methods of DNA sequencing with examples.

4. Overview of the Human Genome Project and its relevance to genomics.

5. Next generation sequencing types and methodologies.

6. Comparison of genetic linkage and physical mapping.

7. Approaches to Metagenomics and their applications.

Multi Omics Introduction

Multi-omics refers to the integrated study of multiple "omics" data sets, such as genomics, transcriptomics, proteomics, and metabolomics. This approach aims to understand complex biological systems by revealing how different biological molecules interact and contribute to cellular function, organismal phenotype, and disease.

Institution: Munster Technological University

Course: BIOL8023

Instructor: Dr. Saravana Periaswamy

Website: www.mtu.ie

What is Genomics?

• Definition: Genomics is the study of an organism's genome, which encompasses all of its DNA, including both coding regions (genes) and non-coding regions (intergenic regions, regulatory sequences, non-coding RNAs, and repetitive elements). It aims to map, sequence, and analyze the entire set of genetic material.

• Distinction from Genetics:

  • Genomics: Focuses on the complete set of genetic information (genome), its structure, function, evolution, and mapping. It investigates interactions between genes, as well as between genes and environmental factors.

  • Genetics: Traditionally focuses on the study of heredity and the function, composition, and inheritance patterns of single genes or a small set of genes. For example, Mendelian genetics studies the inheritance of specific traits.

• Key Concepts:

  • Genome: The complete genetic information of an organism, organized into chromosomes in eukaryotes and largely circular DNA in prokaryotes. It includes all coding sequences, regulatory sequences, and non-coding DNA elements.

  • Gene: A specific sequence of DNA that encodes a functional molecule, typically a protein or a functional RNA (like tRNA or rRNA). Genes are the fundamental units of heredity.

What is DNA?

• Definition: DNA (Deoxyribonucleic Acid) is a macromolecule that contains the unique biological instructions essential for the development, survival, growth, and reproduction of all known organisms and many viruses. It is composed of a long chain of nucleotides.

• Transmission: DNA is faithfully passed from adult organisms to offspring during reproduction, ensuring the continuity of genetic information across generations.

Location of DNA:

• Eukaryotes:

  • Primarily found in the nucleus (as chromosomal DNA, tightly packed with proteins into chromatin) and also in specialized organelles like mitochondria (as mitochondrial DNA, a circular molecule).

• Prokaryotes:

  • Located in the nucleoid (a region within the cytoplasm containing the chromosomal DNA, typically a single circular molecule) and often in smaller, circular DNA molecules called plasmids (which can carry genes for traits like antibiotic resistance).

Structure of DNA

• Double Helix Components:

  • DNA is structured as a double helix, resembling a twisted ladder. It is composed of two long strands that coil around each other.

  • Each strand has a backbone made of alternating phosphate groups and deoxyribose sugars, linked by strong phosphodiester bonds.

  • The two strands are held together by hydrogen bonds between nitrogenous bases, which project inward from the sugar-phosphate backbone:

  • Bases:

    • Adenine (A) always pairs with Thymine (T) via two hydrogen bonds.

    • Guanine (G) always pairs with Cytosine (C) via three hydrogen bonds.

    • The sequence of these bases carries the genetic information.

    • The two strands are antiparallel, meaning they run in opposite directions, with one strand oriented 5' o 3' and the other 3' o 5'.

DNA Replication

• Definition: DNA replication is the biological process of producing two identical copies of DNA from one original DNA molecule. This process is semi-conservative, meaning each new DNA molecule consists of one original (parental) strand and one newly synthesized (daughter) strand.

• Significance: Essential for cell growth, repair, development, and reproduction, ensuring that each new cell receives a complete set of genetic instructions.

Process of DNA Replication:

1. Initiation:

   • The DNA double helix unwinds at specific points called origins of replication, creating replication forks where synthesis begins.

3. Template Function:

   • Each separated single strand serves as a template for the synthesis of a new complementary strand. DNA synthesis always proceeds in the 5' o 3' direction.

5. Enzymatic Process:

   • This process is coordinated by a complex machinery of enzymes and proteins:

   • Helicase: Unwinds and separates the two parental DNA strands by breaking the hydrogen bonds between complementary base pairs.

   • Primase: An RNA polymerase that synthesizes a short RNA primer, providing a free 3'-OH group onto which DNA polymerase can add nucleotides.

   • DNA Polymerase: The main enzyme responsible for synthesizing new DNA strands. It adds deoxyribonucleotides (dNTPs) that are complementary to the template strand in the 5' o 3' direction. It also has proofreading 3' o 5' exonuclease activity to correct errors.

     • The leading strand is synthesized continuously in the 5' o 3' direction towards the replication fork.

     • The lagging strand is synthesized discontinuously in short segments called Okazaki fragments, each requiring a new primer, also in the 5' o 3' direction, but overall moving away from the replication fork.

   • Exonuclease: Enzymes that remove nucleotides from the end of a DNA strand. DNA Polymerase I has 5' o 3' exonuclease activity to remove RNA primers and fill the gaps with DNA, and 3' o 5' exonuclease activity for proofreading.

   • Ligase: Joins the Okazaki fragments on the lagging strand, and seals any nicks (breaks in the phosphodiester backbone) in the DNA strands by forming new phosphodiester bonds.

DNA Sequencing

• Description: DNA sequencing is a laboratory technique used to determine the exact order of nitrogenous bases (A, T, C, G) within a DNA molecule. It reveals the genetic information that organisms carry.

Applications of DNA Sequencing:

• Molecular Biology: Identifying genes, regulatory sequences (e.g., promoters, enhancers), studying gene expression, and understanding gene function and interactions. It's crucial for cloning and genetic engineering.

• Cancer Screening: Detecting somatic mutations in tumor DNA for diagnosis, prognosis, and guiding personalized cancer therapies. It can also identify inherited predispositions to cancer.

• Microbiology: Characterizing organisms that are difficult to isolate or culture, identifying novel species, tracking pathogen outbreaks, and studying antimicrobial resistance.

• Forensic Science: Identifying individuals through DNA profiling (e.g., crime scene analysis, paternity testing, victim identification).

• Agriculture: Screening seeds and livestock genetics for desirable traits, disease resistance, and crop improvement. It aids in plant and animal breeding programs.

Development of DNA Sequencing

• 1958: Francis Crick proposed the