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Mendel and the Gene Idea

Mendel and the Gene Idea. Marie Černá. 1. Uniformity of F1 generation identity of reciprocal crosses During formation of gametes: 2. Principle of segregation two alleles of one gene separate from each other into two gametes 3. Principle of combination - independent assortment

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Mendel and the Gene Idea

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  1. Mendel and the Gene Idea Marie Černá

  2. 1. Uniformity of F1 generation identity of reciprocal crosses During formation of gametes: 2. Principle of segregation two alleles of one gene separate from each other into two gametes 3. Principle of combination - independent assortment alleles of two or more allelic pairs (genes) assort independently of one another there are as many types of gametes as possible random combinations of paternal and maternal chromosomes (genes on different chromosomes behave independently) MENDEL’S LAWS

  3. Dihybrid cross 2 allelic pairs (genes) carried by different pairs of homologous chromosomes – segregate independently two types of parental crosses P: AABB x aabb AAbb x aaBB F1: AaBbdoubleheterozygote genotypes of gametes: AB Ab aB ab 1 : 1 : 1 : 1

  4. F2 Punnett square: Genotypes of gametes

  5. F2 Genotypes: AABB AABb AAbb AaBB AaBb Aabb aaBB aaBb aabb 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1 = (1 : 2 : 1)(1 : 2 : 1) Phenotypes: A-B- A-bb aaB- aabb 9 : 3 : 3 : 1 = (3 : 1)(3 : 1)

  6. Trihybrid cross 3 allelic pairs (genes) four types of parental crosses P: 1) AABBCC x aabbcc 2) AABBcc x aabbCC 3) AAbbcc x aaBBCC 4) AAbbCC x aaBBcc F1: AaBbCc 8 types of gamets: ABC ABc AbC Abc aBC aBc abC abc 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1 F2: 64 of zygotic combinations

  7. Calculations of ratios: by combinatory square (Punnett square) by combination of monohybrid ratios (1AA:2Aa:1aa)(1BB:2Bb:1bb)(1CC:2Cc:1cc) by the calculation of probabilities

  8. Polyhybrid cross n – number of followed genes number of gametes 2n number of zygotes 4n genotype ratio: ( 1 : 2 : 1 )n phenotype ratio: ( 3 : 1 )n

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