The sole question presented by this appeal is the weight to be given a properly administered blood test that shows non-paternity. The trial court instructed the jury that blood tests are not conclusive on the issue of nonpaternity but that the- results of such tests are to be considered along with all the other evidence in determining the issue of paternity. The 'Court of Appeals awarded a new trial, saying that the instruction as given was erroneous, and that the court should have charged that under the law of genetics and heredity a man and woman of blood group “0” cannot possibly have a child of blood group “A,” and that if they believed the testimony of the doctor and believed that the tests were properly administered, it would be their duty to return a verdict of not guilty.
Cases from other jurisdictions involving the question before us are collected in Annot., 46 A.L.R. 2d 1000 (1956). The positions taken by other courts are summarized by the Supreme Court of Nebraska in Houghton v. Houghton, 179 Neb. 275, 285-86, 137 N.W. 2d 861, 869 (1965) :
“In cases arising either under . . . statutes or by courts which have taken judicial notice of the reliability of such *151tests, the courts are not in harmony as to the weight to be given to such evidence. . . . Some cases have held that blood tests indicating nonpaternity are only entitled to the same weight as other evidence. Among them are Arais v. Kalensnikoff, 10 Cal. 2d 428, 74 P. 2d 1043, 115 A.L.R. 163; Berry v. Chaplin, 74 Cal. App. 2d 652, 169 P. 2d 442; and Ross v. Marx, 24 N. J. Super. 25, 93 A. 2d 597. The reasoning of the courts holding this view is stated in Aráis v. Kalensnikoff, swpra, as follows: ‘Expert testimony “is to be given the weight to which it appears in each case to be justly entitled.” * * * “When there is a conflict between scientific testimony and testimony as to the facts, the jury or trial court must determine the relative weight of the evidence. . . . ” ’
“The courts of other jurisdictions, while holding the results obtained from tests are not conclusive on the issue of nonpaternity, do hold that such tests should be given great weight. See, Commonwealth v. Gromo, 190 Pa. Super. 519, 154 A. 2d 417; State ex rel. Steiger v. Gray, Ohio Jur., 145 N.E. 2d 162; Beck v. Beck, 153 Colo. 90, 384 P. 2d 731. . . .
“[There is] a third rule followed by some courts. . . . It is that, in the absence of evidence of a defect in the testing methods, blood grouping tests are conclusive on the issue of nonpaternity. See, Anonymous v. Anonymous, 1 App. Div. 2d 312, 150 N.Y.S. 2d 344; Saks v. Saks, 189 Misc. 667, 71 N.Y.S. 2d 797; Jordan v. Davis, 143 Me. 185, 57 A. 2d 209; Commonwealth v. D’Avella, 339 Mass. 642, 162 N.E. 2d 19; Commonwealth v. Coyle, 190 Pa. Super. 509, 154 A. 2d 412; Retzer v. Retzer (D.C. Mun. App.), 161 A. 2d 469.”
 In North Carolina, when paternity is in issue, statutes require that upon motion by defendant the court order blood tests for mother, child and alleged father. G.S. 49-7; G.S. 8-50.1. G.S. 8-50.1 further provides that “ . . . The results of such blood grouping tests shall be admitted in evidence when offered by a duly licensed practicing physician or other qualified person.” Neither statute prescribes the weight to be given such evidence.
 It is a well-settled principle of statutory construction that where a statute is intelligible without any additional words, no additional words may be supplied. 2A Sutherland Statutory Con*152struction § 47.38 (4th ed., 1973) ; State v. Humphries, 210 N.C. 406, 186 S.E. 473 (1936). Here, it is clear that G.S. 49-7 and G.S. 8-50.1 allow the results of blood-grouping tests into evidence, but the statutes are silent regarding the weight to be given such results. “Where the language of a statute is clear and unambiguous, there is no room for judicial construction and the courts must give it its plain and definite meaning, and are without power to interpolate, or superimpose, provisions and limitations not contained therein.” 7 Strong, N. C. Index 2d, Statutes § 5 (1968). This rule was applied in Board of Architecture v. Lee, 264 N.C. 602, 142 S.E. 2d 643 (1965). In that case, the North Carolina Board of Architecture, pursuant to G.S. 83-12, sought to enjoin the defendant from practicing architecture without a license. An exemption to the licensing requirement provided: “ . . . Nothing in this chapter shall be construed to prevent any person from making plans or data for buildings for himself.” (Emphasis added.) One of the buildings construction of which was sought to be enjoined was an automobile sales and service building to be located on defendant’s property. Defendant had drawn the plans for the building, though he planned to lease it to others. The Board contended that “for himself” in the statute meant buildings that defendant would actually occupy. This Court disagreed. Justice Parker (later Chief Justice), speaking for the Court, said:
“ ... It seems plain that the statutory exception contemplates possession by the designer of the building for whatever lawful purpose he may choose. If the General Assembly had intended the statutory exception to be limited to buildings actually occupied by the designer, and not for lease and use by the public, it could quite easily have said so. . . . The General Assembly having thus formally and clearly expressed its will, the Court is without power to interpolate or superimpose conditions and limitations which the statutory exception does not of itself contain.”
 More recently, we applied this rule to the question now before us. In State v. Fowler, 277 N.C. 305, 177 S.E. 2d 385 (1970), Justice Sharp, speaking for the Court, said:
“There can be no doubt that a defendant’s right to a blood test is a substantial right and that, upon defendant’s motion, the court must order the test when it is possible to do so. However, as Professor Stansbury has pointed out, both G.S. 49-7 and G.S. 8-50.1 are silent as to the weight *153to be given to the blood tests. Stansbury, N. C. Evidence (2d Ed., 1963) § 86 n. 7. See, 33 N.C. L. Rev. 360 n. 15 (1955) ; 27 N.C. L. Rev. 456-457 (1949). Since the statutes do not make the test which establishes nonpaternity conclusive of that issue but merely provide that the results of such test ‘when offered by a . . . duly qualified person’ shall be admitted in evidence, it seems clear that the legislative intent was that the jury should consider the test results, whatever they might show, along with all the other evidence in determining the issue of paternity. [Citations omitted.] ”
The opinion of the Court of Appeals is well reasoned and documented, and cogently presents the view of many jurisdictions that blood-grouping tests that point to nonpaternity are conclusive. Indeed, this Court, recognizing the reliability of such tests, has said: “ . . . Blood-grouping tests which show that a man cannot be the father of a child are perhaps the most dependable evidence we have known. See Note, 50 N.C. L. Rev. 163 (1971).” Wright v. Wright, 281 N.C. 159, 172, 188 S.E. 2d 317, 326 (1972). Perhaps the General Assembly should provide that the results of such tests showing nonpaternity should be conclusive. However, when public policy requires a change in a eonstitutionally-valid statute, it is the duty of the Legislature and not the courts to make that change. 2 Strong, N. C. Index 2d, Constitutional Law § 10 (1967) ; Clark’s v. West, 268 N.C. 527, 151 S.E. 2d 5 (1966) ; Insurance Co. v. Bynum, 267 N.C. 289, 148 S.E. 2d 114 (1966) ; Fisher v. Motor Co., 249 N.C. 617, 107 S.E. 2d 94 (1959). “ ... As long as [the legislative body] does not exceed its powers, the courts are not concerned with the motives, wisdom, or expediency which prompt its actions. These are not questions for the court but for the legislative branch of the government. State v. Warren, 252 N.C. 690, 114 S.E. 2d 660; Ferguson v. Riddle, 233 N.C. 54, 62 S.E. 2d 525; State v. Harris, 216 N.C. 746, 6 S.E. 2d 854.” Clark’s v. West, supra. “The legislative, executive, and supreme judicial powers of State government shall be forever separate and distinct from each other.” Article I, section 6, North Carolina Constitution.
For the above reasons, we adhere to the interpretation of the statute as set out in State v. Fowler, supra, and leave to the General Assembly the question of the weight to be given such blood-grouping tests.
*154The cause is returned to the Court of Appeals for remand to the Superior Court with direction that the judgment entered by Judge Friday be affirmed. The decision of the Court of Appeals is reversed.
Chief Justice Bobbitt not sitting.