HEREDITY AND EVOLUTION 1
• Theinheritanceofcharacteristicsthroughgenerationsiscalledheredity.• Theinheritablecharacteristicsmaybemorphological/anatomical/physiological/reproductiveandareknownastraits.
• GregorJohannmendelcarriedoutseveralexperimentsonheredity.• Mendelconcludedthatoutofanypairofcontrastingcharacters,oneisdominantandtheotherisrecessive.• The homozygous dominant trait is denoted by two capital letters whereas the homozygous recessive trait isdenotedbytwosmallletters.
• Theexpressionofmorphologicalcharactersiscalledphenotype.• Theexpressionofgeneofanindividualforaparticulartraitiscalledgenotype.• The genotype of a character is influenced by genes. Genes are the factors which form the physical basis forinheritanceofcharacters.
• Thealternateexpressionofthesamegenearecalledalleles.• Thecontrastingpairofallelesmakeupanallelomorph.• Organismsdifferinexpressingphenotypewhichleadstovariation.• ChangesoccurringintheDNAofgermcellsareheritablewhereaschangestakingplaceinthenon-reproductivetissuesarenotinherited.
• CharlesDarwinproposedthatevolutionofspecies is influencedbynaturalselection,buthedidnotknowtheunderlyingmechanism.
• Evolutionisaslowprocessandhasoccurredovermillionsofyears,asrevealedbyfossilevidences.• Theageoffossilscanbedeterminedbyusingtherelativemethodortheisotopedatingmethod.• Evolutionhasresultedinthediversityoforganisms.• Allhumanbeings,whetherfairskinnedordarkskinned,belongtothesamespeciesi.e.,Homo sapiensthatoriginatedinAfrica.
• The human ancestors gradually migrated from Africa to various parts of the world such as Asia, Europe,AustraliaandAmerica.Thustheyspreadtodifferentpartsoftheearthandadaptedasbestastheycouldtotheirenvironmentalconditions.
• GeneticengineeringisthemodificationofthegeneticinformationoflivingorganismsbymanipulationofDNAbyadding,removingorrepairingpartofgeneticmaterial(DNA)andchangingthephenotypeoftheorganism.ItisalsoknownasgenemanipulationorrecombinantDNATechnology(r-DNATechnology)
• Bio-technology has contributed towards exploitation of biological organisms or biological processes throughmoderntechniqueswhichcouldbeprofitablyusedinmedicine,agriculture,animalhusbandryandenvironmentalcleaning.
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