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EE, , _ NAVAS CHEEMADAN, 03, PRINCIPLES OF INHERITANCE, AND VARIATION, , Mendel’s Laws on Inheritance, Principles of inheritance!, , Based on Mendel's observations on, monohybrid crosses, Mendel proposed two, Beneral rules to consolidate his understanding of, inheritance inmonohybrid crosses. Today these, rules are called the Principles or Laws of, Inheritance:, , +, , ist Law or Law of Dominance, , 2- Second Law or Law of Segreg, , 1. Law Of Dominance (1* law), The main points are, |. The controlled by, discrete units called factors., Il, Factors occur in pair., Min pairs, (Heterozygous), one member of ‘pairs, the othef. (The, dominated one is called Doftinant,, and, other character is called Recessive), , characters are, , a dissimilar of factors, , 1, , dominates over, , , , , , This law is used to explain the expression of, only one of the parental character in the F1 of, ‘monohybrid cross., This law explains the proportion of 3:1, obtained at the F2, , , , , , 2. Law of segregation, (24 law/law of purity of gamete), , This law is based on the fact that the alleles, do not show any blending and that both the, characters are recovered as such in the F2, generation though one of these is not seen at, the Fi stage, This aw states that,, , “During gamete formation 2 factors for a, , character present in an individual will, , SOHSS AREEKODE VIDEO LESSON, , NAVAS CHEEMADAN, , , , , , Bar, , gare, , een ant satelite eared, , navas885@zmeilcom, separate from each other and enter into, each gamete, such that a gamete receives, only one of the two factors.”, , goate OY, , % Thus, a homozygous parent produces all, , gametes that are similar., While @ Heterozygous one produces two kinds, ‘of gametes each having one allele with equal, Proportion., , Both 1* and 2™ law of Mendel obtained from, monohybrid cross, , DEVIATION FROM MENDELIAN PRINCIPLE/., NON MENDELIAN INHERITANCE, »/Non-Mendelian inheritance is any pattern, ‘of inheritance in which traits do not, Segregate in accordance with Mendel's, laws, In, t inheritance in which the, heterozygous offspring show intermediate, character between 2 parents., ymple-1, > Inheritance of flower colourin the dog, flower (snapdragon or Antirrhinum sp.) and, Mirabilis jalopa (4 o' clock plant) is a good, example to understand incomplete, dominance. It was studied by Carl Correns, of Germany, , AR, (Red), , R), , > it is the in, , xe, (oi te), , OP) >, , Fl RY pink, , GENETICS FOCUS AREA/2022, , , , navass885@gmailcom, , , , , , , , , , , , a, &,, 2 co, cates WAGON cmc, ©, > When Correns crossed a true-breeding red- commen TT, flowered (RR) Antirrhinum and true Example-2, breeding white-flowered Antirrhinum plants Starch grai Pea seed, , (0), the F2.(Re) was pink, > When the F1 was self-pollinated the F2, resulted in the following ratio, , (RR) Red: 2 (Rr) Pink: 1 (er) White., , Here the genotype ratios were exaetly as, we would expect in any/“mendelian, monohybrid cross, but the phenotype, ratios had changed from.thé’3:1 dominant:, , > Starch synthesis in pea seeds is controlled, By One'Bene. It has two alleles (B and b), > BB-—-->starch synthesized effectively, (Large sized starch grains), bb-——-> lesser efficiency in starch, synthesis (Small sized starch grains), >» Bb——+ Intermediate sized starch grains, , 2. Co Dominance, , > Here both alleles of gene are expressed in, bateremennee cnmdition,
