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The Genetic Revolution: Challenge for the Dietetics Profession The Human Genome Project will change


2. Include human genetics as a topic area on the RD. exam ... The human genome is organized into 46 chromosomes. ... Both genetics and environmental factors ... – PowerPoint PPT presentation

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Title: The Genetic Revolution: Challenge for the Dietetics Profession The Human Genome Project will change

The Genetic Revolution Challenge for the
Dietetics Profession The Human Genome
Project will change the practice of
dietetics forever. (White, J. JADA 100 (9)996)
  • Dr. Betty J. Larson
  • Concordia College
  • Moorhead, MN 56562

We are not all alike
  • It will be possible to identify the genes that
    influence susceptibility to a disease.
  • Once the gene is detected, MNT can be matched to
    the individual to prevent or effectively treat
    the disease.

When it comes to
one size does not fit all!

The Challenge Are you ready for this client?
  • A clients laboratory results show that he is
    heterozygous for ABC1 and has a null genotype for
    XYZ2. He has been referred to you for counseling
    on a diet appropriate for his genotype.

The correct response for the client
  • The client has an inherited susceptibility to
  • The recommended diet would include large amounts
    of certain vegetables, special techniques for
    meat preparation

American Dietetic Association recommends that to
be ready for the future we should
  • 1. Require courses on diet-gene interactions
  • 2. Include human genetics as a topic area on the
  • exam
  • 3. Develop internet-based communication and
  • information hub for dietetics professionals
  • 4. Sponsor training at ADA meetings
  • 5. Begin dialogue regarding a new practice
  • in diet and genetic counseling
  • 6. Encourage a health care system where personal
    counseling on diet-gene interactions is valued
    and reimbursed.

Purpose of this presentation is to help us to be
ready for the future
  • Explain the Human Genome Project
  • Define genetic terms
  • Show relationship between genetics and nutrition
  • Recognize ethical issues
  • Demonstrate how these genetic principles utilized
    in genetic engineering of foods

The Cell

example of the amino acid sequence that

makes up the protein vasopressin
Human Genome Project
  • Started in 1990
  • An international research program that will
    complete the mapping and sequencing of all DNA in
    the human body

DNA (deoxyribonucleic acid)
  • The chemical inside the nucleus of a cell that
    carries the genetic instructions for making
    living organisms.
  • DNA exists as 2 paired or complementary strands
    forming a double helix.
  • Each strand of DNA is made up of millions of
    chemical building blocks called bases
  • (A) Adenine
  • (T) Thymine
  • (C )Cytosine
  • (G) Guanine

  • The 4 bases are strung along a repetitive sugar
    (doxyribose phosphate backbone)
  • The 2 strands of DNA are held together by pairing
    of the chemical bases.
  • Adenine forms hydrogen bonds with thymine and
    cytosine forms hydrogen bonds with guanine.
  • Bases are connected to each other by hydrogen
    bonds, abnormalities in these bonds cause some
    genetic diseases. Folic acid in prevention of
    neural tube defect may help overcome a defect in
    bonding and arrangement of bases at the cellular
    level in certain women.
  • DNA holds the codes for making the body proteins

  • When the genetic code is switched on to make a
    protein, the information is copied, base by base,
    from DNA into a single new strand of
    complementary RNA.
  • RNA is single stranded, its backbone is ribose
    and it contains uracil instead of thymine.
  • Transcription is the process of events by which
    sequence of bases on DNA is copied to RNA.
  • Translation is the sequence of events that
    converts the mRNA into a specific protein.

Nutrition plays a role at the level of gene
  • Process of transcription and translation can be
    controlled at several levels. There is a
    promoter region on DNA, initiator sequence,
  • Multiple iron-sulfur clusters are in the cell
    cytoplasm and they respond to the bodys iron
    status by impacting the half-life/stability of
    transferrin mRNA to control the production of the
    transferrin protein.
  • In low iron the transferrin receptor mRNA has a
    longer, half-life thereby producing more
    transferrin mRNA to be translated into
    transferrin receptor proteins. Once made these
    transferrin receptor proteins increase uptake of

  • Iron also controls ferritin synthesis at the
    level of translation.
  • Zinc, Copper, Cadmium, Vitamin A and Vitamin D
    can all influence gene expression.
  • Very clear that vitamins and minerals dont just
    regulate as co-enzymes or cofactors for enzymes,
    but control transcription of genes,
    post-transcription and translation.
  • A better understanding of this process will
    clarify mutations in human disease.

Genetic Code
  • Every 3 bases (called a triplet or condon) along
    a strand of DNA specifies an amino acid to be
    incorporated into a protein, in what is called
    the genetic code.
  • The triplet composed of the bases guanine,
    cytosine, and adenine is the genetic triplet code
    for the amino acid alanine.
  • GAA, ATT, ATG are all examples of condons
  • In the ctyoplasm, the mRNA attaches to ribosomal
    RNA and one codon at a time sequentially directs
    the assembly of amino acid molecules into
    proteins. It may be ready-to-go or new
    post-translation processing.

  • A gene is a segment of a DNA that encodes
    instructions that allow a cell to produce a
    specific protein such as an enzyme or a receptor
    or carrier protein.
  • The functional and physical unit of heredity
    passed from parent to offspring. Genes are pieces
    of DNA, and most genes contain the information
    for making a specific protein.

  • Each gene is composed of long stretches of DNA
    that can be divided into 3 separate classes.
  • Exons - parts of the gene that actually provide
    the specific instructions (the coding region) for
    making a protein
  • Introns - noncoding stretches of DNA
  • In addition to exons and introns each gene also
    contains a noncoding region at its beginning that
    serves to regulate when, and to what extent, the
    gene is expressed. It is the regulatory region
    of the gene (on-off switch). That responds to

  • One of the threadlike "packages" of genes and
    other DNA in the nucleus of a cell.
  • Each chromosome contains many genes.
  • Bases are the letters, codons the words, genes
    the sentences and chromosomes the chapters on how
    to put together the human.

Human Genome
  • The genetic material within our cells contains
    the complete set of instructions for making an
    organism, called its genome.
  • The human genome is the entire manual. Every
    cell contains the entire genome.
  • The human genome is organized into 46
    chromosomes. Of these chromosomes, 44 are in 22
    pairs (autosomes) in which one chromosome is
    inherited from Mom and one from Dad. In
    addition, females inherit an X chromosome from
    each parent, whereas males inherit an X
    chromosome from Mom and a Y from Dad.

Your genes are like…
  • …a hand youve been dealt in a game of cards.
  • Theres nothing you can do about the cards so you
    just have to do the best with what you have.

Genetic Variation
  • Although thousands of random changes occur every
    day in the DNA of a cell as a result of heat and
    metabolic accidents, only a few accumulate in a
  • Remarkable repair mechanisms travel the strand of

Microarray Analysis
  • A computer applies tiny dots of DNA from
    different genes to a glass slide in a grid-like
  • Then it uses ultraviolet light to detect abnormal

Genetics vs. Environment
  • Genetics determines susceptibility to disease,
    but whether or not a predisposed individual
    develops the disease may depend on environmental
    factors such as nutrition.

How are genes related to nutrition?
  • Digestion
  • Absorption
  • Metabolism
  • Excretion
  • Taste

Metabolic Differences
  • Vitamin and mineral needs
  • Sodium levels
  • 30-60 of variance due to genetics
  • Cholesterol
  • 50 of variance due to genetics
  • Fiber affecting cholesterol
  • Phytochemical effectiveness
  • Bone Density
  • 75 of variance due to genetics

Diseases Linked to Genetics
  • Hypertension
  • Obesity
  • Diabetes Mellitus
  • Cancer
  • Osteoporosis
  • Alzheimers Disease
  • Cystic Fibrosis

  • The Pima Indians in Arizona and in Sonora Mexico
    share the same genetic make-up but the Arizona
    population has the highest prevalence of Type II
    Diabetes Mellitus in the world, whereas their
    Mexican counterparts are lean and healthy.
    (Bennett, PH (1999) Nutrition Reviews 57S61-S64
    and Valencia, ME, et al (1999) Nutrition Reviews
    57 S55-58)
  • Bouchard demonstrated with identical twins that
    although the genetic predisposition existed for
    obesity, development of obesity was not a forgone
    conclusion. (Bouchard, et al (1990) NEJM

Obesity Continued
  • Therefore, while we might be genetically
    predisposed to obesity, our environment and diet
    allows it to occur.
  • Furthermore, genetic make-up appears to determine
    which obese individuals benefit from particular
    diet therapies and even exercise. (Barsch et al
    (2000) Nature 404644-651, and Chagnon et al
    (2000) Obesity Research 889-117, and Martinez
    et al (2000), Eruopean J. Clin Nutrition 54

Gluten-Sensitive Enteropathy
  • Individuals with gluten-sensitive enteropathy
    have a genetic pre-disposition but do not
    manifest the disease if they do not eat gluten.
    They still have the genes but dietary intake
    prevents expression of the gene.

(Murray, Am J. Clin. Nutr (1999) 69 354-365)
  • Individuals with a common genetic variation in
    the 5,10-methyl-enetetrahy-drofolate reductase
    gene are predis-posed to increased levels of
    homocysteine (a risk factor for CVD. You do not
    develop increased levels if you consume adequate
    folate. Nutrition fills the genetic gap.

Kang (1988) Am J. Hum Genet 43414-421. Jacques
(1996) Circulation 937-9. Verhoeff (1998)
Atherosclerosis 141161-166)
  • Genetic variability in components in the
    renin-angiotension-aldosterone system have
    correlated with hypertension and its response to
    a low-salt diet.

Coronary Heart Disease
  • Both genetics and environmental factors influence
    risk of CHD.
  • Genes influence levels of total cholesterol,
    lipoproteins, hypertension and obesity

  • Which apolipoprotein E variants (apoE 2, 3, or 4)
    individuals have affects their risk of CVD and
    their response to dietary manipulation.
    (Simopoulos (1999) Nutr Rev 57S10-S19).
  • For example, the common advice to increase PS
    ratio benefits men with genotype ApoE4/ApoE3 or
    (4/3) but not women with the ApoE 3/2 genotype.
    (Cobb et al (1992) Circulation 86849-857.)
  • Oat Bran promotes a hypocholesterolemic response
    in those with the ApoE 3/3 genotype but not in
    those with 4/4 or 4/3. (Uusitupa, et al (1992) J
    Am Coll Nutr 11651-659.

Lipoprotein Study
  • General population is divided into two groups
    Phenotype A and B
  • Phenotype A large, buoyant LDL
  • Phenotype B small, dense LDL
  • At higher risk for CHD
  • Krauss, Dreon. Low density lipoprotein
    subclasses and response to a low-fat diet in men.
    Am. J. Clin. Nutr (supppl) 1995
  • Identification of genetic polymorphisms that
    influence lipoproteins and CHD risk eventually
    will lead to genetic markers for this disease.
  • The same genetic factors that determine an
    individuals blood lipid profile and CHD risk
    will also influence response to diet.

Diet Response related to Genes
  • 72 premenopausal women and 105 healthy adult men
    consumed low fat diets for 6-8 weeks
  • Both men and women in the Phenotype B group were
    shown to have a decrease in the total number of
    LDL particles
  • Although, 41 of Phenotype A showed an adverse
    affect with a change to more of the atherogenic
    Phenotype B patterned LDLs
  • Dreon, Fernstom, Miller FASEB J. 8L121m 1994
  • Dreon, DM, Krauss, RM Circulation 86 (suppl)
    1-405, 1992

Cancer Risk
  • Inherited or spontaneous occurrence?
  • Only 5-10 is inherited, but those individuals
    have an 85 chance of getting breast cancer
  • Also, they are at higher risk for reoccurrence
    and ovarian cancer
  • It is now identifiable so these individuals can
    be monitored more closely

Plant Phytonutrients
  • The plant phytonutrients genistein and quercetin
    appear to work at the level of gene expression to
    decrease the risk of prostate and liver cancer,

Davis, et al (1999). Nutr Cancer
35167-174. Kang, et al (1999). Nutr Cancer
Alzheimers Experiment
  • Injected a gene into the brain that causes
    production of a nerve growth factor
  • It is hoped this factor will be able to reproduce
    the missing factor and reverse the disease

Ethical Issues
  • Misinterpretation and misuse of information
  • Personal rights
  • Do we want to know?

Dietitians perspective
  • Not just genetics…
  • Genomics
  • The study of genes and how they influence health
    and disease
  • Its our responsibility to understand the
    connections between genes, nutrition, and disease

Knowledge of genetics is not only important for
MNT but for an understanding of our food!
  • The health professional must be able to explain
    the use of biotechnology in food development
    because consumers are confused.
  • In Europe they refer to our new foods as

Biotechnology is the application of living
organisms to develop new products
  • The terms genetic engineering, recombinant DNA
    (rDNA) technology, gene splicing and genetic
    modification often are used interchangeably.
  • These phrases refer to specific processes used in
    biotechnology, describe the movement or transfer
    of genetic material from one source to another.

Applications of Biotechnology
  • Products of biotechnology were commonplace
    centuries before Watson and Crick defined the
    structure of DNA.

In 1800 BC with the use of fermentation, humans
first used microorganisms to produce wine,
beer and leavened bread.
Biotechnology holds great promise
  • Biotechnology has potential in the fields of
    medicine, environmental protection, food
    production and agriculture.

Biotechnology provides opportunities for
protection of the environment
  • Genetically modified bacteria may be used to
    convert organic wastes from municipalities into
    useful products, including sugar, alcohol and
    methane compounds that can be alternative fuels.

Opportunities in food production
  • Chymosin was first approved in the US in 1990 as
    a pure enzyme from genetic engineering that
    replaces rennet in the production of cheese.

Opportunities in Agriculture
  • In 1994, the first genetically engineered plant
    food product, a vine-ripened tomato, was
    available to consumers.

Plant biotechnology is the addition of selected
traits to plants to develop new plant varieties.
  • Allows for the transfer of a greater variety of
    genetic information in a more controlled manner
    than traditional plant breeding.

  • Disease protection, which provides intrinsic
    protection from a specific virus or fungal
  • Insect protection, which provides intrinsic
    protection from targeted pests.
  • Tolerance to a specific environmentally
    compatible herbicide, allowing for more effective
    weed control.

Improved nutritional value
  • Golden rice with improved vitamin A content could
    reduce blindness in developing countries.
  • Bananas which would convey resistance to cholera.

Organizations recognize the safety of
  • The American Dietetic Association
  • American Medical Association
  • National research Council
  • World Health Organization

Myths and Facts about Food Biotechnology
  • Myth 1 The application of biotechnology to
    crops and food is very different from traditional
    agricultural methods.
  • Myth 2 Foods produced using biotechnology have
    not been established as safe nor are they
    adequately regulated.
  • Myth 3 The application of biotechnology to food
    only benefits food producers not consumers.

Myths Continued
  • Myth 4 Without special labeling, consumers face
    unknown risks from food biotechnology.
  • Myth 5 Crops produced using biotechnology will
    negatively impact the environment.
  • Myth 6 The production of crops resistant to
    certain pests and weeds will lead to Super Bugs
    and/or super Weeds immune to existing methods
    of pest and weed management.

Myths Continued
  • Myth 7 biotechnology cannot relieve world
  • Myth 8 The long-term effects of foods developed
    using biotechnology are unknown.