AIIMS: Revision Terminology Part 9

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  • Light Dark forms (Both belong to one sp. Now as 2 forms – typical & carbonaria of B. betularia)

  • Hybrid breakdown – when offspring of hybrids are infertile

  • Cell anemia – glutamic acid is replaced by valine in the 6 Beta position of autosomal recessive lethal gene = 0.4 frequency of carrier in population of 200 individual is p2 + 2pq +q2 = 1 die due to lethal So 2pq = 2 x 0.6 x 0.4 = 0.48 and N = 200, So freq. of carrier = 0.48 x 200 = 96

  • Hot spots – sites which are more mutable then other sites (Benzer) e.g. smethyl Cytosine residues

  • More closely related sexual partners less are variations in their off springs.

  • Classical / forward genetics – study of phenotype, analysis & isolation of concerned genes & study of DNA sequence comprising genes.

  • Reverse genetics – if we start DNA Seq. study from phenotypic effect of which we do not know & then introduce in some animal to study its phenotypic effect.

  • Blending of inheritable chromosome is the intermingling of heredity material of both offspring’s.

  • Mendel’s success – pea easy to cultivate, naturally self-pollinated, artificially cross-pollinate.

  • Mendel’s success – sharply defined inherited differences in difference varieties, only one variable at a time

  • In rr seeds in small DNA Fragment interferes with SBE – 1 so starch in not formed and it accumulates as sugar – causer high osmotic pressure lead to shrinkage & wrinkling.

  • Dihydric cross - inheritance of seed color is independent of seed shape.

  • Homozygous - condition in which only one allele is present of a pair

  • Mendel used element for factor -> gene

Understanding the F1, F2 and F3 generations

Mendel's Cross

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  • Genotype exhibiting difference phenotype under difference environmental conditions – Individual norm of reaction

  • Same environment & genotype but phenotype differ due to difference in internal environment = Developmental noise

  • 2 different genotype produce same phenotype due to different environment & have difference genotype = phenocopies of each other

  • If a dwarf plant introduced tall by gibberellin acid then too it would behave as dwarf genetically.

  • In haploid organism – chromosome are governed only by one allele then law of dominance & Segregation do not apply.

  • Locus = position of allele on chromosome

  • Back cross Tt X any parent

  • Test cross Tt X recessive (tt) Phenotype = 1 : 1 : 1 : 1

  • Hugo – de Vries (Dutch) cosrrens(Germany) Tschermark (Austrian) -> Mendel’s work as principles & coined term factor

  • Bateson – 1st announced Mendel’s work in England (poultry, rabbit, sweet pea)

  • Bateson coined homozygous, heterozygous, allomorphs – “ Mendel’s principle of heredity”

  • Nageli advised Mendel to work on Hieracium (But he failed) seeds produced without pollination

  • Mendel = 1st genetic surgeon

Genotype and Phenotype

No Of gene pair












  • Genetic markers => Alleles.

  • Albinism = autosomal recessive mutation. If 1st child of a normal pair in albino what is the is the probability of 2nd child for albino = 25% (due to recessive chromosome so only homozygous condition will show albinism)

  • Tt x Tt -> tt(25%) = answer

  • 1st child is independent of the 2nd child

  • What would be proportion of Tt Yy Ss Dd Ee from a cross

  • Tt Yy Ss Dd Ee X Tt Yy Ss Cc Dd Ee

  • Answer: of progeny will be

  • TT, yy, Ss, Cc, dd, Ee.

  • x x x x x = answer