Question

Differentiate between the following -
(a) Dominance and Recessive 
(b) Homozygous and Heterozygous 
(c) Monohybrid and Dihybrid.

Answer 1

(a) Dominance and Recessive

-	Dominance	Recessive
1.	A dominant factor or allele expresses itself in the presence or absence of a recessive trait.	A recessive trait is able to express itself only in the absence of a dominant trait.
2.	For example: tall plant round seed violet flowers etc. are dominant characters in a pea plant.	For example: dwarf plant wrinkled seed white flower etc. are recessive traits in a pea plant.

(b) Homozygous and Heterozygous

-	Homozygous	Heterozygous
1.	It contains two similar alleles for a particular trait	It contains two different alleles for a particular trait.
2.	Genotype for homozygous possess either dominant or recessive but never both alleles. For example RR or rr	Genotypes for heterozygous possess both dominant and recessive alleles. For example Rr
3.	It produces only one type of gamete.	It produces two different kinds of gametes.

(c) Monohybrid and Dihybrid

-	Monohybrid	Dihybrid
1.	Monohybrid involves a cross between parents which differs in only one pair of contrasting characters.	IDihybrid involves a cross between parents which differs in two pairs of contrasting characters.
2.	For example, the cross between tall and dwarf pea plant is a monohybrid cross.	For example, the cross between pea plants having yellow wrinkled seeds with those having green round seeds is a dihybrid cross.