Question

Distinguish between homozygous and heterozygous plants.

Answer 1

Hint: Mendel proposed that in a true-breeding, tall or dwarf pea variety the allelic pair of the gene for the height are identical, TT and tt, respectively. An individual having two different alleles (Tt) will be called hybrid. Bateson and Saunders termed these conditions as homozygous and heterozygous respectively.

Complete answer:
Following are the differences between homozygous plants and heterozygous plants.

Homozygous Plant	Heterozygous Plant
The homozygous plant will be having identical alleles for a single trait. An allele represents one particular form of a gene.	In the heterozygous plant, heterozygous refers to an individual having two different alleles for a specific trait. It contains two different copies of alleles coding for a particular trait.
Homozygous alleles may be dominant or recessive. A homozygous dominant allele combination contains two dominant alleles and expresses the dominant phenotype (expressed physical trait). A homozygous recessive allele combination contains two recessive alleles and expresses the recessive phenotype.	Contains different alleles for a trait. Both dominant and recessive. Although homologous chromosomes have the same genes, they may have different alleles for those genes. Alleles determine how particular traits are expressed or observed.
In the homologous plant, repetition of the same trait can be observed after self-fertilization	In the heterozygous plant, self-fertilization results in different combination of traits over the next generations
Only one type of gamete is produced	Two types of gametes are produced
It can be either homozygous dominant or homozygous recessive	Heterozygous alleles can show complete dominance, codominance or incomplete dominance

Additional information:
Complete dominance: Incomplete dominance inheritance, one allele is dominant and the other is recessive. The dominant trait is observed and the recessive trait is masked.
Incomplete dominance: One of the heterozygous alleles does not completely mask the other. Instead, a different phenotype is seen that is a combination of the phenotypes of the two alleles.
Codominance: Both of the heterozygous alleles are fully expressed in the phenotype. An example of codominance is AB blood type inheritance.

Note: Mendel was able to propose that when two dissimilar factors are present in a single individual, only one can express and other is not. The one that expresses itself is called the dominant factor while the one that fails to express is termed as the recessive factor.