Genetics The study of inherited characteristics www. sliderbase.

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sveta_slayd.ppt

  • Размер: 253.0 Кб
  • Автор: Ботакоз Дели
  • Количество слайдов: 6

Описание презентации Genetics The study of inherited characteristics www. sliderbase. по слайдам

Genetics The study of inherited characteristics www. sliderbase. com Genetics The study of inherited characteristics www. sliderbase. com

Monohybrid inheritance Let the allele for round seeds be:  R (dominant allele) LetMonohybrid inheritance Let the allele for round seeds be: R (dominant allele) Let the allele for wrinkled seeds be: r (recessive allele) Parents phenotype round seeds x wrinkled seeds genotype RR rr Gametes F 1 generation R R r r F 1 phenotypes 100% plants producing round seeds F 1 genotypes 100% heterozygotes Rrgametes. RR r. Rr. Rr gametes www. sliderbase. com

Does the observed ratio match theoretical ratio?  • The theoretical or expected ratioDoes the observed ratio match theoretical ratio? • The theoretical or expected ratio of plants producing round or wrinkled seeds is 3 round : 1 wrinkled • Mendel’s observed ratio was 2. 96: 1 • The discrepancy is due to statistical error • The observed ratio is very rarely the same as the expected ratio • The larger the sample the more nearly the results approximate to theoretical ratio • Statistical tests such as the chi-squared test can be used to test the closeness of fit of the observed and theoretical ratios www. sliderbase. com

 • F 1 intercross • Parents phenotype   round seeds x round • F 1 intercross • Parents phenotype round seeds x round seeds genotype Rr • Gametes • F 2 generation R r r. R Phenotype 75% plants producing round seeds 25% plants producing wrinkled seeds Genotype 25% RR 50% Rr 25% rr Ratio 3: 1 Round seeds: wrinkled seedsgametes. Rr RRRRr r. Rrrr www. sliderbase. com

 • The use of the term F 1 generation is limited to the • The use of the term F 1 generation is limited to the offspring of two homozygous parents • The use of the term F 2 is limited to the offspring of intercrossing the F 1 generation • In all other cases the terms offspring (1) and offspring (2) should be used • The complete set of headings will be: Parents phenotypes Parents genotypes Gametes Offspring (1) genotypes Offspring (1) phenotypes Gametes Offspring (2) phenotypes Offspring (2) genotypes. What if the parents are not homozygous? www. sliderbase. com

Backcross To test whether a plant producing round seeds is homozygous RR  orBackcross To test whether a plant producing round seeds is homozygous RR or heterozygous Rr it can be crossed with a homozygous rr plant If plant is homozygous dominant RR Parents phenotype round x wrinkled genotype RR rr gametes Offspring If plant is heterozygous Rr Parents phenotype round x wrinkled genotype Rr rr gametes Offspring. R R r r rgametes. RR r. Rr. Rr gametes. Rr r. Rrrr Offspring phenotype 100% round Genotype 100% Rr Offspring phenotype 50% round 50% wrinkled genotype 50% Rr 50% rr www. sliderbase. com