Which one of the following symbols and its representation, used in human pedigree analysis is correct?
Correct answer: A. Mating between relatives
- A. Mating between relatives
- B. Unaffected male
- C. Unaffected female
- D. Male affected
Explanation
A record of inheritance of certain genetic traits for two or more generations presented in the form of a diagram or family tree is called a pedigree. In a pedigree, a square represents the male, a circle the female, solid (blackened) symbol shows the trait under study or affected individual; unaffected or normal individual by an open or clear symbol and a cross or shade (of any type) in the symbol signifies the carrier of a recessive allele. Words can also be used in place of symbols. Parents are shown by a horizontal line while their offspring are connected to it by a vertical line. The offspring are then shown in the form of a horizontal line below the parents and numbered with Arabic numerals.
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About Inheritance
Mendel's laws explain segregation, independent assortment and the prediction of genetic ratios using alleles, genotypes and phenotypes. The chapter also covers linked genes, recombination and crossing over during meiosis, then applies pedigree reasoning to X-linked recessive traits, which show different inheritance patterns in males and females.
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