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About Us

Established in 1979, the Johns Hopkins DNA Diagnostic Laboratory is a CLIA and CAP certified; Maryland, New York, and Pennsylvania licensed clinical genetics testing laboratory specializing in rare inherited disorders. Led by renown professor of pediatrics and medical genetics Dr. Garry R. Cutting, the lab offers testing for a range of approximately 50 phenotypes and disorders totaling 3,500 tests annually. Techniques include: 

  • Exome/Zoom
  • Next Generation Sequencing (NGS; sequence and deletion/duplication analysis) 
  • Sanger sequencing
  • PCR/fragment analysis

In addition to its core mission, the Johns Hopkins DNA Diagnostic Laboratory is also proud to serve as the Cystic Fibrosis Foundation’s Mutation Analysis Program (MAP) Laboratory.

The lab's website is intended for the use of health care providers and we are not able to consult directly with patients. Health care providers and patients may find some helpful resources on our Patient and Family Resources page.

  • Garry R. Cutting, M.D.

    Professor, Department of Pediatrics  & McKusick-Nathans Institute of Genetic Medicine
    Medical Laboratory Director

    Dr. Cutting earned his BS in Biology from the University of Connecticut and his MD from the University of Connecticut Medical School.  He completed a fellowship in Pediatric Genetics at the Johns Hopkins University School of Medicine.  His research is focused on the genetic and non-genetic causes of disease variation in cystic fibrosis (CF) and there are three major active projects in his research laboratory: 

    • CF Twin and Sibling Study
    • Genetic Heterogeneity in CF
    • CFTR2 Project

    The CF Twin and Sibling Study seeks to identify the major genetic and environmental factors that cause variation in the CF phenotype.  Genome-wide linkage and association methods are employed to find loci and genes that modify quantitative traits (lung function, BMI) and qualitative complications (diabetes and meconium ileus) of CF.  The Genetic Heterogeneity study is investigating families recruited by the laboratory that have 2 or more individuals where linkage excludes involvement of CFTR.  Exome sequencing is being used to discover new genes that create a CF-like phenotype.  CFTR2 is a worldwide project involving ~70,000 CF patients to clinical and functionally annotate all mutations in the CFTR gene.  

    Read more about Dr. Garry R. Cutting

    Molly B. Sheridan, Ph.D.

    Assistant Professor, Department of Pediatrics & McKusick-Nathans Institute of Genetic Medicine
    Laboratory Director

    Dr. Sheridan earned a BS in Biology from The College of New Jersey and a PhD in Cellular and Molecular Medicine from Johns Hopkins University. She completed a research post-doctoral fellowship in genetics at Children’s Hospital of Philadelphia in 2011. Dr. Sheridan returned to Johns Hopkins University in 2011 to complete a combined Clinical Cytogenetics and Clinical Molecular Genetics fellowship.   She joined the McKusick-Nathans Institute of Genetic Medicine faculty in 2015. She is board-certified by the American Board of Medical Genetics and Genomics in Clinical Cytogenetics and Clinical Molecular Genetics.

    Sumathi Rachamadugu MSc, MS, CGC

    Genetic Counselor for DNA Diagnostic Lab at Johns Hopkins Genomics

    Sumathi Rachamadugu MSc, MS, CGC earned a master's degree in biomedical genetics from Vellore Institute of Technology in India, followed by a master's degree in genetic counseling from the University of Utah. She has worked as a cytogenetic technologist in India, and has several years of work experience as a clinical genetic counselor in the general genetics and adult cardiovascular clinics. Before joining Johns Hopkins Genomics, Sumathi worked at Intermountain Healthcare where she was team lead for the adult cardiovascular genetic counseling program, and served on various committees influencing genetic counseling, including a population study return of results committee. Sumathi is passionate about genetics education for non-genetics medical providers, learning the art and science of variant classification, and implementing technology to automate and scale the genetic counseling workflow. She is board-certified by the American Board of Genetic Counseling, and is an active member of the National Society of Genetic Counselors.

    Sabrina Ingram, BS

    Billing Coordinator

    Sabrina’s role within the lab is to coordinate the billing.  She is responsible for making sure the billing process is easy and simple for the referrers requesting testing. She also plays a role in the financial aspects of the JHDDL, such as Budget Reports, Reimbursements and AP/AR.  After relocating to Baltimore, Sabrina obtained a degree in Business Administration from Sojourner-Douglass College in Baltimore, Maryland.  She has worked for Johns Hopkins University for more than 12 years and enjoys working with clients and the laboratory technical staff. 

    Christopher O'Donnell, MS

    Quality Assurance Administrator

    Chris leads the the laboratory Quality Assurance program, ensuring compliance with laboratory regulations set forth by CLIA, College of American Pathologists (CAP) and other state agencies.  He received a Bachelor of Science in Biological Sciences with a minor in History from Virginia Tech and a Master of Science degree in Biotechnology with a concentration in Regulatory Affairs from Johns Hopkins University.  

  • Proficiency Testing: Participant in CAP Surveys, Inter- and Intra-laboratory comparison challenges.

  • Telephone: 410-955-0483
    Fax: 410-367-3266

    Postal Address (not for shipping samples)

    Johns Hopkins Genomics - DNA Diagnostic Laboratory
    1812 Ashland Ave, Room 200
    Baltimore, MD 21205


    General questions and information:
    Billing questions and information:

    Other Helpful Numbers at Johns Hopkins

    General number for Johns Hopkins Hospital: 410-955-5000


    Garry Cutting, M.D.
    Medical Director

    Molly B. Sheridan, Ph.D.
    Laboratory Director

    Client Services Staff

    Sumathi Rachamadugu M.Sc., M.S., CGC
    Genetic Counselor
    General Department Email:
    Phone: 443-927-3089
    Fax: 410-367-3266

    Sabrina Ingram, B.S.
    Billing Coordinator
    Billing Department Email:
    Phone: 443-287-2486
    Fax: 410-367-3266

    Hours of Operation

    Monday-Friday 8:00AM to 4:30PM Eastern Time
    Closed on weekends and official holidays

    Holiday Hours

    The lab will be closed on the following holidays:


    When the lab is closed, no personnel will be present to answer phone calls or accept deliveries.

    The lab is not open on weekends for sample delivery.

    Please plan your specimen shipments accordingly.

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