Mono Hybrid Cross
MONOHYBRID CROSS - DEFINITION
A cross made to study the inheritance of one character or two contrasting forms or two different alleles is known as monohybrid cross.
Crossing of pure tall (TT) and dwarf (tt) to observe the inheritance of height character or two contrasting forms (Tall, Dwarf) or two different alleles (T t). Such crossing is called mono hybridisation and resultant ‘F1’ progeny is called monohybrids.
PHENOTYPIC EXPLANATION OF MONO HYBRID CROSS
Mendel crossed pure tall plant with pure dwarf plant. To do this, he transferred pollen grains of tall plant (male parent) to the stigma of dwarf plant (female parent or emasculated parent). It is called normal cross.
In another cross, Mendel transferred the pollen grains of dwarf plant (male parent) to the stigma of tall plant (female parent or emasculated parent). It is called reciprocal cross.
In both the above crosses, Mendel got all ‘F1’ monohybrid tall plants. Why ‘F1’ progeny is tall? This resulted him to propose the principle of dominance.
B. Law of Dominance - Definition:
Mendel proposed this principle by observing ‘F1’ progeny.
Law of dominance states that when a pair of contrasting forms (Tall, Dwarf) were crossed, the contrasting form that expressed (Tall) in ‘F1’ generation is called dominant contrasting form. The contrasting form that did not express in ‘F1’ generation is called recessive contrasting form (Dwarf).
In the above experiment tall is dominant over dwarf. What happened to the recessive allele, dwarf in ‘F1’?
To find out the answer for above Question, Mendel continued the experiment. 2. Dominance/Recessiveness When two unlike unit factors responsible for a single character are present in a single individual, one unit factor is dominant to the other, which is said to be recessive. In each monohybrid cross, the trait expressed in the F1 generation is controlled by the dominant unit factor. The trait not expressed is controlled...