Basics of Genetics - Vo - VS I - 2024-25 PDF

1 Overview and Basics Basic Terminology and Concepts - Genetics – study of genes and heredity (how qualities or traits are passed from parents to o8spring) - DNA – molecule carrying genetic information to code for development and function of an organism - Gene – segment of DNA containi...

1 Overview and Basics Basic Terminology and Concepts - Genetics – study of genes and heredity (how qualities or traits are passed from parents to o8spring) - DNA – molecule carrying genetic information to code for development and function of an organism - Gene – segment of DNA containing instructions for building molecules, primarily proteins - Exons - segments of the gene encoding proteins - Introns - segments of the gene not coding proteins - Protein – large molecule responsible for many di8erent functions in an organism - Chromosomes – structures which store DNA - Genome – complete set of genetic material present in each cell nucleus and/or an individual DNA makes up genes and is spooled within chromosomes inside organism the nucleus of a cell. Credit: NIGMS. https://www.nigms.nih.gov/education/fact-sheets/Pages/genetics.aspx westernu.edu  Genetics and Eyecare - An estimated 6% of the total population will be a8ected by monogenic disease (disease caused by single gene mutation) - 1 in 2000 individuals have a monogenetic inherited retinal disease2 - you will likely see patients with a genetic condition, many with visual impairments, and will be asked how this will a8ect their livelihood and future - More importantly, an increasing number of breakthrough treatment options are being developed for previously uncurable eye disease - be ready! 1. In: Rodwell, C., Aymé, S. (eds.) (2014). 2014 Report on the State of the Art of Rare Disease Activities in Europe Part Ii: Key Developments in the Field of Rare Diseases in Europe in 2013. 1–90. http://www.eucerd.eu/upload/Ule/Reports/2014ReportStateofArtRDActivities.pdf. westernu.edu 2. Berger W, Kloeckener-Gruissem B, Neidhardt J. The molecular basis of human retinal and vitreoretinal diseases. Progress in Retinal and Eye Research. DNA Overview - DNA (deoxyribonucleic acid) – double- stranded helical shaped molecule carrying genetic information - Each strand has a backbone of an alternating pentose sugar (deoxyribose) and phosphate groups which are attached to one of four nucleobases: - adenine (A) - guanine (G) - cytosine (C) - thymine (T) - Adenine and guanine are purines (2 ring structures) https://www.genome.gov/genetics-glossary/Deoxyribonucleic- - Cytosine and thymine are pyrimidines (1 Acid ring structures) - This complex of a nucleobase, sugar (deoxyribose), and phosphate group is referred to as a nucleotide westernu.edu DNA Overview - DNA strands are consistently oriented in opposite directions from the other - Each strand has a 5’ end and a 3’ end - In replication and translation, polymerases work in the 5’ to 3’ direction - The 3’ end is thus referred to as the tail end - This nomenclature comes from how we number the carbons of the ribose sugar found in each nucleotide - 1st carbon after the oxygen, in clockwise order https://homework.study.com/explanation/what-does-dna-only-bu ilds-in-the-5-3-prime-direction-mean-is-the-leading-strand-alway s-5-3-and-is-the-lagging-strand-always-3-5.html westernu.edu ’  DNA Overview - This span of gene sequences is very long, so DNA must be tightly coiled and compressed - DNA compresses tightly into strands and coil around spool-like proteins called histones - the combination of histones and this DNA is referred to as a nucleosome - The collection of nucleosomes, when aggregated, makeup a large structure called chromatin - Chromatin can vary in how densely it is packed, which a8ects how easy it is for other molecules to access genetic information Heterochromatin – tightly condensed Euchromatin – loosely condensed Chromatin is condensed and forms a chromosome Histone – National Human Genome Research Institute westernu.edu 1. https://www.genome.gov/genetics-glossary/Deoxyribonucleic-Acid https://www.genome.gov/genetics-glossary/histone  DNA Overview - This span of gene sequences is very long, so DNA must be tightly coiled and compressed - DNA compresses tightly into strands and coil around spool-like proteins called histones - the combination of histones and this DNA is referred to as a nucleosome - The collection of nucleosomes, when aggregated, makeup a large structure called chromatin - Chromatin can vary in how densely it is packed, which a8ects how easy it is for other molecules to access genetic information Heterochromatin – tightly condensed Euchromatin – loosely condensed Chromatin is condensed and forms a Dna Deoxyribonucleic Acid 3-D – National Human Genome Research Institute https://youtu.be/L9NriBoubWE chromosome westernu.edu 1. https://www.genome.gov/genetics-glossary/Deoxyribonucleic-Acid Chromosomes Chromosomes are located in the cell nucleus Contain two short arms and two long arms Short arm (p) Long arm (q) Arms are held together by the centromere Tips of arms are capped by sections of DNA called telomeres which protect the chromosomes during DNA replication Sex chromosome – chromosome involved in sex determination (X and Y) Autosome – any chromosome that is not a sex chromosome https://geneticeducation.co.in/chromosome-deUnition-structure-fun ction-and-classiUcation/ westernu.edu Chromosomes Humans have 46 chromosomes in somatic cells (non-sex cells), arranged as 23 pairs Half is inherited from the mother, half from the father These pairs are referred to as having a diploid number of cells (2n) One pair decides the patient’s gender X and Y chromosomes XY = male XX = female Sex cells gametes (sperm, ova) have a haploid number(1n) and combine during fertilization to form a paired set Forrester, John V. The Eye: Basic Sciences in Practice. 4th edition. Saunders Ltd.; 2015. of chromosomes as a zygote westernu.edu RNA RNA (ribonucleic acid) - single-stranded structure with only a single ribose sugar similar nucleobases as DNA, except uracil (U) instead of thymine (T) (uracil is still a pyrimidine) This complex of these nucleobases, sugar (ribose), and phosphate group is referred to as a ribonucleotide RNA functions facilitates translation of DNA into polypeptides also carry out various biochemical reactions and other regulatory roles in cells Review Three nucleobases make-up a codon A codon is responsible for the creation of an amino acid Two or more amino acids make-up a peptide https://byjus.com/biology/structure-of-rna/ A chain of peptides are known as a polypeptide polypeptides of a certain length are known as proteins westernu.edu Types of RNA mRNA (messenger RNA)- RNA produced in the nucleus from a DNA template directs the synthesis of new proteins tRNA (transfer RNA) – RNA that binds to amino acid on one end and to ribosomal RNA at the other Matches genetic information from an mRNA strand to speciUc amino acids rRNA (ribosomal RNA) – cytoplasmic RNA – National Human Genome Research Institute https://www.genome.gov/genetics-glossary/RNA-Ribonucleic-Acid RNA where protein assembly takes place Assembles with proteins to form ribosomes that help with protein synthesis ribosome – small dense granules of RNA and protein that assemble amino acids into proteins westernu.edu DNA replication Cells pass on genetic information to subsequent generations of cells via replication DNA replication is semi-conservative, meaning new DNA has an old (“conserved”) DNA strand from the parent cell and one new created DNA strand 1. Helicase unwinds the parent DNA 2. Primase adds a short strand of RNA primer to each single strand of DNA to mark the starting point of replication 3. DNA polymerase begins at the RNA primer and synthesizes new strand of DNA on the parent strand, working in the 5’ to 3’ direction DNA Replication – National Human Genome Research Institute 1. Leading strand – strand where DNA polymerase and helicase are https://www.genome.gov/genetics-glossary/DNA-Replication working continuously in the same direction. 2. Lagging strand – DNA polymerase and helicase work in opposite directions in short segments 4. DNA polymerase binds to the lagging strand to synthesize shorter DNA fragments (Okazaki fragments) also in the 5’ to 3’ direction 5. Exonuclease removes all RNA primers from each strand 6. Okazaki fragments on the lagging strand are joined by DNA ligase to form the completed strand DNA Replication - yourgenome https://www.youtube.com/watch?v=TNKWgcFPHqw westernu.edu  Protein Synthesis DNA Urst produces a mRNA strand through the process of transcription mRNA - single strand of codons which correspond to a particular amino acid Codons - 3 base sequences Amino acids - compounds which are incorporated into proteins 22 amino acids make up the thousands of diYerent proteins found in the body westernu.edu Yang, Jinliang & Pu, Haitao & Lian, Jian & Gu, Jason & Fan, Mingqu. (2018). Modeling and Analysis of Protein Synthesis and DNA MutaGon Using Colored Petri Nets. IEEE Access. PP. 1-1. 10.1109/ACCESS.2018.2825782.  Protein Synthesis - Transcription Transcription: Initiation: enzyme known as RNA polymerase binds to DNA at promoter region Elongation: RNA polymerase unwinds DNA and synthesizes complementary mRNA strand in 5’ to 3’ direction Termination: RNA polymerase reaches a termination sequence on the DNA strand to stop elongation and releases mRNA strand out of the nucleus and into the cytoplasm Transcription – National Human Genome Research Institute https://www.genome.gov/genetics-glossary/Translation westernu.edu  Protein Synthesis - Translation Using this new single mRNA strand, ribosomes within the cell cytoplasm reads the strand and translates this sequence of codons to create the Translation – National Human Genome Research Institute polypeptide chain/protein https://youtu.be/oCp9IK6iBTo?si=X70qVuiRiHhRaIVx Ribosomes are dense granules which serve as the primary site of protein synthesis in the cell Mostly made of rRNA and ribosomal proteins yourgenome https://www.yourgenome.org/facts/what-is-rna/ westernu.edu Protein Synthesis - Translation Translation Initiation: mRNA binds to tRNA and the small ribosomal subunit. This complex then is attached to the large ribosomal subunit Elongation: new tRNAs bring amino acids which correspond to the codons of the mRNA Termination: stop codon is reached, enzyme cleaves bond between tRNA and peptide chain, peptide chain is released Most proteins are not active immediately after translation and are completed Translation – National Human Genome Research Institute https://youtu.be/oCp9IK6iBTo?si=X70qVuiRiHhRaIVx within the rough ER and Golgi apparatus westernu.edu  Ribosome Structure The ribosome is composed of two main chunks known as subunits The size of each subunit is di8erent in prokaryotes vs eukaryotes Prokaryotes have 70S ribosomes Small (30S) Large (50S) Eukaryotes have 80s ribosomes Small (40S) Large (60S) The “S” is a Svedberg unit that indirectly represents a particle’s size and Ribosomes - Structure and Functions composition https://alevelbiology.co.uk/notes/ribosomes-structure-and-functions/ Ribosomes are complex structures that are dircult to quantify in size/weight, so the Svedberg unit is used to measure its size based on its sedimentation rate westernu.edu  Ribosome Structure Prokaryotes: 70S - Small (30S), Large (50S) Eukaryotes: 80s - Small (40S), Large (60S) Example: a class of drugs called macrolides are antibiotics which bind to only the 50S subunit of the ribosome, unique to prokaryotes (i.e. bacteria) This signiUcant inhibits bacterial protein synthesis by preventing translation Erythromycin, azithromycin, clarithromycin are examples of macrolides Similarly, tetracyclines mainly bind to the 30S subunit to also inhibit protein synthesis Tetracycline, doxycycline, minocycline are all tetracyclines GoodRx – Erythromycin ophthalmic ointment 0.5%, Doxycycline hyclate 100 mg https://www.grxstatic.com/ westernu.edu TOPHAT westernu.edu 2 Genetic Expression and Mutations Gene Expression and Regulation Gene expression – process by which the information encoded in a gene turns into a function Expression is predominantly limited by the rate of transcription of mRNA, which controls when, where, and how much RNA and protein are produced The degree of compaction of chromatin in regions of a gene limits the ability of proteins and enzymes to gain access to the gene for transcription Heterochromatin – tightly condensed, preventing transcription Euchromatin – loosely condensed, promoting transcription Steroid hormones and growth factors can bind to intracellular receptors, activating transcription and promoting gene expression Open chromatin (euchromatin) opens the arrangement of nucleosomes and DNA for transcription to more readily occur https://www.10xgenomics.com/blog/is-single-cell-epigenomics-right-for-me-atac-ing-your-res earch-questions-for-deeper-insights westernu.edu  Gene Mutations - Substitutions Mutation – permanent change in the nucleotide sequence of DNA Mutations are largely harmless, but some lead to cell death or tumor formation Substitution – aka point mutations. Change in single nucleotide base Most common mutation Transition – purine substituted with another purine (e.g. A for G) or pyrimidine to pyrimidine (T for C) Transversion – purine substituted for pyrimidine (e.g. T for A) or vice-versa This single change can lead to a few di8erent outcomes: Silent mutation – newly created codon codes for the same amino acid as original Nonsense – new codon is a stop codon, causing early termination of protein synthesis and a non- functioning protein https://www2.csudh.edu/nsturm/CHEMXL153/DNAMutationRepair.htm Missense – newly created codon creates a di8erent amino acid and thus an alternation in protein function westernu.edu  Gene Mutations - Deletions and Insertions Substitution – aka point mutations. Change in single nucleotide base Deletion – one or more base pairs are lost from the DNA, often creating a frameshift mutation where the entire amino acid sequence is altered. Often lead to nonsense mutations. Insertion – one or more base pairs are added, also potentially leading to frameshifts If multiples of three base pairs are inserted or deleted, this prevents a frameshift https://www2.csudh.edu/nsturm/CHEMXL153/DNAMutationRepair.htm westernu.edu Alleles Human cells carry two copies of each chromosome, meaning there are two versions of each gene Alleles - di8erent versions of a gene Alleles commonly occur in pairs Paired, identical alleles = genotype is homozygous for a particular trait Paired, di8erent alleles = genotype is heterozygous for a particular trait Alleles may also be dominant, recessive, or codominant Allele for brown eye (B) is dominant, blue eye allele is recessive. If person has both alleles (Bb), they will have https://www.yourgenome.org/facts/what-are-dominant-and-recessive-alleles brown eyes westernu.edu  Other Mutations Trinucleotide repeat mutation – error in replication where an abnormal number of repated trinucleotides present in a gene Huntington’s disease, fragile X, myotonic dystrophy increase in severity with each successive generation with successive generations due to lengthening trinucleotide repeat Translocations – movement of part or all of a gene to another location within the DNA Entire chromosomes may be gained or loss through meiosis Down syndrome: extra copy of chromosome 21 https://www.verywellhealth.com/myotonic-muscular-dystrophy-symptoms-4570998 westernu.edu DNA Mutations and Cancer Cancer – disease characterized by uncontrollable cell growth Commonly the result of multiple mutations within cells over time Oncogenes – positively insuence tumor formation Tumor-suppressor genes - negatively impact tumor Oncogene growth by producing proteins https://www.genome.gov/genetics-glossary/Oncogene promoting apoptosis and/or inhibition of cell proliferation westernu.edu DNA Mutations and Cancer Protooncogenes – groups of genes which help cells grow and divide normally cause normal cells to become cancerous when mutated Considered the precursors to oncogenes Produce proteins inhibiting apoptosis (programmed cell death) and/or promote cell proliferation westernu.edu  Germline vs Somatic Mutations Germline (constitutional) mutations – mutation originating in reproductive cells Sperm and egg pass from parents to children, so mutation is inherited and generally incorporated in all cells of o8spring Minority of cancers are from germline mutations/variants Examples: Sickle cell, breast cancer, retinoblastoma, cystic Ubrosis, Tay-Sachs Somatic mutation – mutation in cells other than reproductive cells Most common cause of cancer and may be caused by carcinogens such as tobacco use, UV light, aging Mutation is acquired, not inherited, and not Retinoblastoma. American Academy of Ophthalmology passed from parent to child https://www.aao.org/image.axd?id=f4867884-085b-4b94-9bf1-4e9000f2b887&t=6359728 32102070000 Examples: Skin cancer, lung cancer, Sturge- Weber westernu.edu Forrester, John V. The Eye: Basic Sciences in Practice. 4th edition. Saunders Ltd.; 2015.  Genomics, Proteomics, and Recombinant DNA Genomics – study of structure, function, evolution, and mapping of genomes Proteomics – study of structure, function, interactions of proteins and their activity as it relates to the organism Recombinant DNA technology – process of manipulating DNA using laboratory techniques to combine DNA, create genes with new functions, and/or repair mutations Various methods are used in genomics and proteomics to analyze https://www.energy.gov/science/doe-explainsgenomics# DNA and proteins https://www.genome.gov/genetics-glossary/Recombinant-DNA-Technology westernu.edu Polymerase Chain Reaction (PCR) AmpliUes segment of DNA to help study the segment in greater detail DNA is denatured to separate the strands and to allow primers to select a segment of the genome to amplify DNA polymerase synthesizes the DNA and creates a copy of the segment Millions of copies can be produced over several cycles Producing a large volume of copies allow for easier detection PCR 3-D https://youtu.be/KIcxzSr6IcE? of mutations si=FrBejzB1ocRa5hms westernu.edu Southern Blot Technique used to detect and quantify a speciUc DNA sequence/gene in a larger sample PuriUed, isolated DNA is cleaved with enzymes to create several DNA fragments Fragments are further separated using an electric current to pass them through a sieve-like gel via electrophoresis Smaller fragments pass through medium faster compared to larger fragments Filter is placed on gel and combined Southern Blot https://www.genome.gov/genetics-glossary/Southern-Blot with a genomic probe which tests if the gene of interest is in the sample westernu.edu Chromosome Analysis (Karotyping) Lab-produced image of person’s chromosomes, arranged in numerical order Allows visual detection numerical of structural abnormalities in chromosomes Can use blood or other body suids (e.g. placenta, aminiotic suid, bone marrow) as sample suids Karyotype https://www.genome.gov/genetics-glossary/Karyotype westernu.edu  Types of Genetic Disorders Genetic disorders have a variety of possible etiologies: Chromosomal Monogenic disorders Autosomal dominant Autosomal recessive X-linked Multifactorial Genetic and environmental factors combine to a8ect how the disease manifests Mitochondrial No transmission from males to o8spring; only mothers pass defective gene to o8spring westernu.edu Forrester, John V. The Eye: Basic Sciences in Practice. 4th edition. Saunders Ltd.; 2015.  Down Syndrome (Trisomy 21) Down syndrome (Trisomy 21) Characterized by extra 21st chromosome Most common chromosomal disorder Findings range signiUcantly, but common features include: Upslanting palpebral Ussures Epicanthal folds Brachycephaly (shorter skull length) Cognitive impairment, typically manifesting in Urst year of life Increased likelihood of behavioral/psychiatric disorders and cardiovascular disease Increased risk of dementia/Alzheimer’s Hearing impairment Increased risk of keratoconus – abnormal progressive thinning of cornea Brush]eld spots – white to grey/brown spots on surface of iris composed of connective tissue (benign) Diagnosed via physical examination and karyotyping westernu.edu Kleinfelter Syndrome (XXY) Kleinfelter Syndrome (XXY) Extra X chromosome(s) in an XY male 80-90% typically have one extra X Characterized by androgen deUciency (gynecomastia, sexual dysfunction, osteoporosis), stunted pubertal development Most common cause of primary hypogonadism – sex glands (testes, ovaries) produce little to no hormones Majority of men with Kleinfelter syndrome are undiagnosed – mean age of diagnosis ~30 years Diagnosed via karyotype and physical examination westernu.edu Turner Syndrome Loss of part of all of X chromosome in females Most common sex chromosome abnormality in females Result in shorter stature, skeletal anomalies and hypogonadism Other Undings: hearing loss, hypothyroidism, liver abnormalities, congenital heart disease Early intervention with hormone therapy and improve liver function and musculoskeletal development Higher likelihood of myopia, strabismus Higher risk of color vision deUciency Diagnosed via karyotype and physical examination westernu.edu Cystic Fibrosis Mutation(s) of CFTR gene resulting in persistent pulmonary infection, pancreatic insurciency, and elevated sweat chloride levels Thicker mucus commonly leads to obstructive lung disease, chronic infection, and respiratory issues Autosomal recessive inheritance Symptoms range from mild to severely debilitating Diagnosed via physical exam, genetic testing, and lab testing of sweat westernu.edu Genetics of Viruses - Virus – infectious microbe containing DNA or RNA surrounded by a protective protein coat known as a capsid - may also contain an outer-membrane envelope - Viruses are obligate intracellular parasites, meaning they can only replicate within host cells, often killing the host cell in the process - Viral genomes may contain di8erent combinations of stranded-ness and nucleic acids Virus - Double-stranded DNA https://www.genome.gov/genetics-glossary/Virus - Double-stranded RNA - single-stranded DNA - Single-stranded RNA westernu.edu Viral Replication Basic steps of Viral Replication 1. Virus binds to host cell Entire virus may enter, or only genetic material 2. Capsid is removed, viral genome is replicated, and new proteins are created 3. Virus is released from cell by rupturing the cell entirely or bud o8 from the surface Antiviral medications you will encounter primarily inhibit DNA polymerase to prevent viral replication Examples: Virus Replication trisuridine (topical eye drop) https://www.mondoscience.com/blog/virus-replication acyclovir (oral) valacyclovir (oral) famvir (oral) westernu.edu  Herpesviridae (herpesviruses) Herpesviridae – family of enveloped, double-stranded DNA viruses tegument – matrix of proteins connecting capsid with the envelope proteins involved in DNA replication and evading immune response Glycoproteins encapsulate the envelope to aid in entering and infecting host cells Can establish lifelong, persistent infections and periodically reactivate, particularly in the https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8923070/ immunocompromised westernu.edu Herpesviruses. In: Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. eds. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. McGraw-Hill Education; 2019.  Herpesviridae (herpesviruses) Examples of human herpes viruses: Herpes simplex viruses, types 1 and 2 Varicella zoster virus Epstein-Barr virus Cytomegalovirus Wide variety of disease associated with herpesvirus infection Herpes simplex viruses Extremely widespread in humans A8ects multiple areas of the body, including genitals, oral cavity, eye, and brain Known for viral latency – virus is dormant Cleveland Clinic 2024 in a cell and does not cause symptoms Herpes Simplex Virus (HSV): Types Symptoms, & Treatment (clevela ndclinic.org) Activation is dependent on various factors (etc. stress, sunlight, immunocompromise) westernu.edu Herpesviruses. In: Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. eds. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. McGraw-Hill Education; 2019.  Herpes simplex viruses Herpes simplex viruses (HSV) HSV-1 – spread by contact with infected saliva Typically results in oral ulcers, but can occasionally a8ect genitals Recurrent infections can include cold sores, fever blisters, and keratitis (corneal damage) HSV-2 –transmitted sexually or from maternal genetical infection to newborn Typically results in genital ulcers, but can a8ect oral cavities Herpes KeraGGs – Core EM Less likely to manifest ocular signs/symptoms Virus must encounter mucosa or broken skin to initiate infection westernu.edu Herpesviruses. In: Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. eds. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. McGraw-Hill Education; 2019.  Varicella-Zoster Virus Varicella-zoster virus responsible for two main disease entities: Varicella (chickenpox) - Mild, highly contagious disease Acute disease following primary contact with virus Skin and mucous membranes develop vesicular sores Herpes Zoster (shingles) – painful, localized skin rash a8ecting adults and immunocompromised Reactivation of virus from latent form May also have ocular involvement Herpes Zoster Ophthalmicus - American Academy of Ophthalmology (aao.org) westernu.edu Herpesviruses. In: Riedel S, Hobden JA, Miller S, Morse SA, Mietzner TA, Detrick B, Mitchell TG, Sakanari JA, Hotez P, Mejia R. eds. Jawetz, Melnick, & Adelberg's Medical Microbiology, 28e. McGraw-Hill Education; 2019.  Viruses and Gene Therapy Gene therapy - ”treatment of a genetic disease by the introduction of speciUc cell function-altering genetic material into a patient” (Bulcha 2021) “…exogenous DNA sequences…are introduced into host cells and those transduced host cells in turn produce a transgene product” (Chung 2009) DNA sequences commonly delivered via viral vectors and/or non-viral methods Working gene for speciUc protein is introduced into a virus, which intentionally invades a host to try to produce the protein Bulcha JT, Wang Y, Ma H, Tai PWL, Gao G. Viral vector platforms within the gene therapy landscape. Sig Transduct Target Ther. 2021;6(1):53. Chung DC, Lee V, Maguire AM. Recent advances in ocular gene therapy. Curr Opin Ophthalmol. 2009;20(5):377-81. westernu.edu http://www.institut-biotherapies.fr/wp-content/uploads/2013/01/exp_VecteurT_ang.jpg  Viruses and Gene Therapy - adeno-associated virus (AAV) has become the vector of choice in recent years due to its high safety proUle and erciency westernu.edu Bulcha JT, Wang Y, Ma H, Tai PWL, Gao G. Viral vector platforms within the gene therapy landscape. Sig Transduct Target Ther. 2021;6(1):53.  The Hope for Gene Therapy LUXTURNA (voretigene neparvovec-rzyl) – FDA approved in 2017 gene therapy treatment for Leber congenital amaurosis (inherited retinal disease causing severe vision loss beginning at infancy) Eligible patients must have a mutation in the RPE65 gene and clinically conUrmed Leber congenital amaurosis Patients demonstrated signiUcant improvement in functional vision, illumination detection, and visual acuity westernu.edu Bennett J. Gene therapy for Leber congenital amaurosis. Novartis Found Symp. 2004;255:195-202 Genetics of Bacteria Bacteria reproduce very quickly, allowing for multiple generations of o8spring and mutations to occur in a short period of time Binary ]ssion – process of cloning the parent bacterium by splitting it in two, creating two identical copies Bacteria can still evolve by incorporating DNA into its genome: transformation – incorporates piece of DNA in its proximity transduction – virus (bacteriophage) incorporates DNA from one bacterium to another conjugation – DNA transfers between bacteria h]ps://www.curioustem.org/stem-arGcles/horizontal-gene-transfer westernu.edu