pedigree analysis (NEET) 12th NCERT biology

Pedigree analysis

one should remember three points to define pedigree analysis
  • it is the the study of a persons' family genetic history or family tree
  • it is made up of symbols and lines 
  • and used to trace Mendelian disorders in a family 
let us understand the above statement of pedigree analysis. one, as compare to the other animal and plants human has a very long life span. it is nearly impossible to make controlled breeding experiments on humans as Mendel had performed on pea plant (pisum sativum). Therefore pedigree analysis becomes most advantageous to learn the pattern of inheritance of a trait or character in a family. it helps us to trace and find the probability of occurrence of Mendelian disorder as these disorders follow Mendelian pattern of inheritance. 

symbols and lines

NCERT Class XII Biology Chapter 5 : Principles of Inheritance and ...

Pedigree can be performed for all the Mendelian disorder such as-

1- autosomal or autosome linked recessive
2- autosomal or autosome linked dominant
3- sex-linked (X-linked) recessive
4- sex-linked (X-linked) dominant

Autosome linked recessive inheritance

  • it always appears in homozygous (in case of identical allele) condition i.e., (aa)
  • it often skips the generation
  • male and female are equally affected or affects both the sexes 

in pedigree analysis how do we decide it is dominant or recessive ...
in this pedigree the parents are unaffected but their progeny are affected, this suggests that parents are carrier (heterozygous- Aa) hence look normal but able to transmit mutation to the next generation.
for the male of third generation of this pedigree comes from unaffected parent and unaffected grand parent i.e., the mutation skips generation and at last the we can see that male and female are affected which suggests that the mutation is linked with autosome.

Autosome linked dominant
  • it appears in both homozygous (in case of identical allele i.e., AA and heterozygous (in case of non-identical allele i.e., Aa) conditions
  • it do not skip the generation
  • male and female are equally affected or affects both the sexes 
in pedigree analysis how do we decide it is dominant or recessive ...

plz follow the youtube link here for NEET problems on pedigree analysis

https://www.youtube.com/watch?v=dlbFUGPKs8o&list=LLcIuvYeMTY5bpc2Olubr7Rg&index=8&t=103s

https://www.youtube.com/watch?v=348-W7Pb7Zg&t=258s

https://www.youtube.com/watch?v=RZ75JWVewmY


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