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Answer» 1. Homozygous and Heterozygous: - There are two genes for every character. If the two genes for a particular character are identical, is said to be homozygous (G homos ⇒ same; zygotes ⇒ a pair). For example, tall plants (TT) & dwarf plant (tt) are homozygous.
- If the two genes for a particular character are unlike, it is said to be heterozygous (G. heteros ⇒ other, zygotes ⇒ a pair). For example, Tt is heterozygous tall.
| Homozygous | Heterozygous | | Formation of only one type of gametes | Formation of 2 types of gametes | | Breed true to the particular character | Do not breed true to a particular character | | It possesses two alleles of a gene | It possesses two identical alleles of a contrasting gene |
2. Dominant and Recessive trait: Dominant character: - Amongst two alleles of a character, the character express in a heterozygous condition is called Dominant character. The incidence is known as Dominance and the gene responsible for it is dominant allele.
- For Example, Tt containing pea plant has T for tallness and t for dwarfness and T is the dominant character.
Recessive character: - Amongst Alleles of a character in the F1 generation, which is not expressed is called recessive character. It expresses only in the homozygous condition of character.
- For Example, tt condition express dwarfness of a plant.
3. Genotype and Phenotype: Genotype: - Genetic expression of a feature, which obtained from parents.
- For Example Pure round seed producing parent plants has genotype R R.
Phenotype: - The visible expression of the hereditary character possessed by an organism.
- For example, around or wrinkled shape of seed is its phenotype.
4. Monohybrid Cross and Dihybrid Cross: Monohybrid cross: - Across in which inheritance of only one pair of contrasting character is studied.
- Dihybrid cross
- Across in which inheritance of two pairs of contrasting characters is studied simultaneously.
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