Principles of Inheritance and Variation Terminologies
Learn about key genetic terminologies such as factor, locus, allele, dihybrid cross, and test cross in principles of inheritance and variation. Understand Mendel's second law, dihybrid crosses, phenotypic ratios, and test cross outcomes through informative images.
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Presentation Transcript
CHAPTER - 5 PRINCIPLES OF INHERITANCE AND VARIATION DIHYBRID CROSS, TEST CROSS 1
Terminologies in Genetics: Factor or Gene: Functional unit of heredity responsible for the expression of character in the progeny. Locus: The position of the gene on the chromosomes. Allele: The alternative form of a gene for a contrasting character present on identical locus of homologous chromosomes.
Inheritance of two gene: Mendel s 2nd law or Law of independent assortment: It states that, factors for different pairs of contrasting characters in a hybrid assorted (distributed) independently during gamete formation. Dihybrid cross: The cross between two parents, which differs in two pairs of contrasting characters.
Dihybrid cross: Parents Round Yellow Wrinkled Green phenotype genotype rryy ry RRYY gametes RY F1 generation RrYy Round Yellow
Dihybrid test cross. F1 hybrid is crossed with recessive green wrinkled pea plant. Recessive green wrinkled rryy, Gamet ry F1 hybrid : round yellow- RrYy, Gamets: RY, Ry, rY, ry. Gam ets RY Ry rY ry ry RrYy Rryy rryY rryy Phenotypic ratio 1 : 1 : 1 :1
TEST CROSS Crossing of F1 individual having dominant phenotype with its homozygous recessive parent is called test cross. The test cross is used to determine whether the individuals exhibiting dominant character are homozygous or heterozygous. 8
TEST CROSS 4:0 ratio Unknown is homozygous dominant TT X tt T Tt T Tt t Tt t Tt 9
Test cross T t 2:2 ration Unknown is heterozygous t Tt tt Tt X tt t Tt tt 10
BACK CROSS 11
10/10 INTRODUCTION (SCD) / SKILL AND CAREER DEVELOPMENT/ SARASWATHI.R/ENG/SNS ACADEMY 15/6/2020
