Answer:
Alleles refer to the alternative form of the same gene. These are mainly of two types: dominant and recessive allele.
The dominant allele is the which mask the effect of another allele in a heterozygous condition. The allele which is masked or which is not able to express itself in a heterozygous condition is termed as a recessive allele.
For example, T (codes for tallness of a plant) is dominant over t which codes for a dwarf trait.
The organisms that contain the same allele for a particular trait is said to be homozygous for that trait. For example, TT and tt.
In contrast, if the organism contains different alleles for a particular trait, it is termed as heterozygous for that particular trait. For example, Tt.
Thus, the first, second, third and fourth blank can be correctly filled with dominant, recessive, homozygous, and heterozygous respectively.
Dominant, recessive, purebred and heterozygous are the correct blanks.
Alleles are the various form of the gene that codes for the various forms of the attribute for the same trait. It can be located in the same position of the gene loci and is passed from both the parent.
The type of allele that overpowers and masks another allele for the same trait is called a dominant allele while the allele that gets masked in the presence of the dominant is called a recessive allele.
The allele carrying the same genetic trait in a pure form is called purebred while the allele that has different forms for the specific attribute is called heterozygous.
Therefore, first, second, third and fourth are the correct options.
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