DEFINITIONS OF IMPORTANT TERMS OF GENETICS
1. Alleles – Alleles are the different alternate form of a particular gene. (OR) Alleles are the genes that govern variations of the same characteristic and that occupy corresponding loci on homologous chromosomes.
2. Back Cross – When a plant is crossed with any of its parents, it is known as Back Cross.
3. Cross – Cross is the mating between two individuals leading to the fusion of gametes.
4. Dihybrid Cross – Cross in which two pairs of contrasting or alternative trait is involved is known as Dihybrid Cross. Example: Tall plant with wrinkled seeds and Short plant with Round seeds (TTrr and ttRR) etc.
5. Dominant Alleles – Dominant alleles are the alleles which express themselves in both homozygous as well heterozygous condition.
6. F1/ First Filial Generation – The progeny (offspring) produced by the mating of individuals in the parental generation is known as F1 generation.
7. F2/ Second Filial Generation – The progeny (offspring) produced by the mating of individuals of F1 generation is termed as F2 generation. (OR) The subsequent generation produced by breeding of F1 offspring is termed as F2 generation.
8. Genes – Genes are the hereditary units. It is present on chromosomes.
9. Genetics – Genetics is a study of heredity.
10. Genotype – Genotype is the term used for Genetic constitution of plants. Example: TT, Tt, RR, rr etc.
11. Heterozygous – An individual that carries two different alleles for a given locus is said to be homozygous for that locus. Example: Aa, Tt, Rr etc.
12. Homozygous – An individual that carries two identical alleles for a given locus is said to be homozygous for that locus. Example: AA, aa, TT, tt, RR, rr etc.
13. Locus – It refers to the site a gene occupies in a chromosomes.
14. Monohybrid Cross – Cross in which only one pair of contrasting or alternative trait is involved is known as Monohybrid Cross. Example: Round and wrinkled (RR and rr); Tall and Short (TT and tt)
15. Phenotype – Phenotype is termed for the physical appearance of plants. Example: Tall, Dwarf etc.
16. Recessive Alleles – Recessive alleles are the alleles which are expressed only in the homozygous condition. Example: tt, rr, ss, aa etc.
17. Test Cross – When a plant is crossed with specifically recessive parents, it is called as test cross.
18. True breeding lines – True breeding lines are those plants which produces progeny exactly like themselves when allowed to self-pollinate.