Assisted reproductive technologies (ART) are special medical techniques used to help infertile couples have a child. In IVF (in vitro fertilisation), the ovum and sperms are collected and fertilisation is carried out outside the body in the laboratory (in a culture dish); the resulting early embryo is then transferred into the uterus (embryo transfer). A baby born by such a technique is commonly (though misleadingly) called a test-tube baby. Other ART methods include GIFT, ZIFT and ICSI.

Law of dominance: characters are controlled by discrete units called factors (genes) which occur in pairs; in a dissimilar pair (heterozygous) of factors, one factor is dominant and expresses itself while the other is recessive and remains masked. Law of segregation: during the formation of gametes, the two factors (alleles) of a pair separate (segregate) so that each gamete receives only one factor of the pair; the factors do not blend and are passed on unchanged.

Mendel's law of independent assortment states that when two pairs of contrasting characters (traits) are considered together, the alleles of one pair of characters segregate (assort) independently of the alleles of the other pair during the formation of gametes. In other words, the inheritance of one character is not affected by the inheritance of another. This law is based on the results of a dihybrid cross, which gives a phenotypic ratio of 9 : 3 : 3 : 1 in the F2 generation.