1. A cross is one that involves two parents who differ in one way with respect to a particular characteristic.
2. One member of a pair of alleles of a gene exhibits dominance if it completely the expression of the other allele in the phenotype resulting from the heterozygote.
3. The members of a pair of alleles show dominance if the heterozygote results in a phenotype between those of the two homozygotes.
4. The members of a pair of alleles show if the heterozygote produces a phenotype where both alleles are expressed.
5. It three or more alleles of a gene exist, it is said to have alleles.
6. Human females posses a pair of homologous sex chromosomes called X chromosomes; human males have one X and a Y chromosome which is to part of the X chromosome.
7. Genes present on an X chromosome but not on a Y chromosome are said to be .
8. A characteristic which shows variation is controlled by alleles of more than one gene and is said to show inheritance.
9. Mutations are changes in the which involve an alteration of type or sequence in DNA or a change in of chromosomes.
10. Substitution and bring about minor changes and are called point mutations; insertion and lead to major changes and are called frameshift mutations.
11. Mutations occur rarely and at . Their frequency can be increased by agents.
12. occurs when a spindle fibre fails during meiosis and the members of a pair of homologous chromosomes fail to separate. This results in some gametes receiving one chromosome too many or one chromosome too few and leads to the formation of individuals suffering chromosome .
13. A pattern of inheritance amongst the members of a family can be established constructing a . Analysis of a family tree relating to a genetic disorder enables a genetic to help people make decisions about parenthood based on assessment of .
14. A is a display of a complement of chromosomes showing their form, size and number.
15. and chorionic villus sampling enable material to be karyotyped and inspected for chromosomal abnormalities.
16. Risk evaluation in cases of polygenic inheritance is usually .
17. Post natal is done to identify babies suffering phenylketonuria.