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Mendelian Genetics

Mendelian Genetics. Genetics Vocabulary. Genetics Vocabulary. Characteristic – something observable that can appear in more than one form. (like eye colour) Trait – a variation that can exist for a characteristic (either brown or blue eyes)

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Mendelian Genetics

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  1. Mendelian Genetics

  2. Genetics Vocabulary

  3. Genetics Vocabulary • Characteristic – something observable that can appear in more than one form. (like eye colour) • Trait – a variation that can exist for a characteristic (either brown or blue eyes) • Allele – one of the possible versions of a gene (you have either the allele for blue eyes, or brown eyes, or both)

  4. Genetics Vocabulary • Phenotype – the appearance of a particular characteristic (if you have blue or brown eyes) • Genotype – the particular genes an organism has. (do you have genes for blue or brown eyes)

  5. Q:What is the relationship between genes (genotype) and observable characteristics (phenotype)?

  6. Q:What is the relationship between genes (genotype) and observable characteristics (phenotype)? A: Phenotype = Genotype + Environment.

  7. For example...

  8. For example... Genetically identical hydrangeas growing in soils of different acidity (different environments).

  9. What did Mendel do?

  10. What did Mendel do? • Mendel saw that all the flowers in the F1 generation were purple. Mendel called the purple trait dominant and the white trait recessive.

  11. What did Mendel do? • Then, Mendel crossed the plants of the F1 generation with each other. Mendel was amazed to see that about ¾ of the F2 generation were purple, and about ¼ were white.

  12. What is up with this???

  13. Mendel figured it out

  14. Mendel figured it out • An organism always has two genes present for each characteristic – one from each parent

  15. Mendel figured it out • An organism always has two genes present for each characteristic – one from each parent

  16. Mendel figured it out • If the alleles on both genes are the same (both express purple or both express white) then the organism is purebred. Organisms with matching alleles are called homozygous.

  17. Mendel figured it out • If the alleles are different then the organism is called a hybrid. One trait (purple) will be dominant, the other one (white) will be recessive. Organisms with different alleles are called heterozygous.

  18. So how does all this explain how we got 75% purple flowers and 25% white flowers in the F2 generation?

  19. PP pp

  20. PP pp Pp

  21. PP pp Pp Pp

  22. PP pp Pp Pp Pp

  23. PP pp Pp Pp Pp Pp

  24. What happens when we cross the F1 generation?

  25. What happens when we cross the F1 generation? • All the F1 generation are Pp • This means they are all heterozygous

  26. What happens when we cross the F1 generation? • All the F1 generation are Pp • This means they are all heterozygous • How do we explain 75% purple and 25% white?

  27. A Punnett Square

  28. A Punnett Square p P

  29. A Punnett Square p P P p

  30. A Punnett Square p P P p

  31. A Punnett Square p P P p

  32. A Punnett Square p P P p

  33. A Punnett Square p P P p

  34. A Punnett Square p P P p

  35. The End

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