Mendel and His Peas

1. Mendel and His Peas

2. Objectives • Explain the difference between cross and self pollination • Explain the relationship between traits and heredity • Describe the experiments of Gregor Mendel • Explain the difference between dominant and recessive traits

3. Heredity is… • The passing of traits from parent to offspring,and it is very complicated • Different people have different traits, such as eye color, hair color, and ear lobes that do not attach directly to their head • Where do people get these different traits? • Many traits are inherited from parents and passed from parents to offspring through genes, which are a set of instructions for an inherited trait

4. Gregor Mendel • Born in 1882 on a farm in Austria • Studied science at a monastery • He discovered the principles of heredity in the monastery garden. Known as the Father of Genetics • His research was mostly on plants • He noticed that often a trait appeared in one generation (parents) and not present in the next generation (offspring)

10. 1 Anther 2 Filament 3 Pistil Female Reproduction organ A Wild Strawberry Flower Male Reproduction organ http://www.countrysideinfo.co.uk/flower.htm

11. http://hordeum.oscs.montana.edu/home/documents/bb.jpg

12. Pollination • Transfer of pollen from the anthers of the stamen to the stigma of the pistil. Fertilization • The union of one egg cell and one sperm cell.

13. Pollination Video Clips • http://www.fotosearch.com/DGV741/620009/ (Bee on flower) • http://video.google.com/videoplay?docid=5294323989667289565 (Importance of Honey Bees in pollination) • The Pollination Song http://www.mbgnet.net/bioplants/pollination.html

14. Self-Pollinating Peas • Mendel wanted to find out more about patterns that traits take on from generation to generation • To keep it simple, he focused on only one kind of organism – peas • Peas are self-pollinating, which means they have both male and female reproductive structures • These are true breeding plants Animation of self-pollination http://www.fs.fed.us/wildflowers/pollinators/images/selfpollination.gif

15. True Breeding • All offspring have the same traits • Examples: • True breeding plants with purple flowers will always produce purple flowers • True breeding plants with long stems will always produce plants with long stems

16. Cross-Pollination • Peas can also cross-pollinate • In cross-pollination pollen from one plant fertilizes the ovule of a flower on a different plant • This can occur from insect travel or by wind Cross-Pollination Animation http://www.fs.fed.us/wildflowers/pollinators/images/xpollination_ani.gif

18. Cross-pollination http://cache.eb.com/eb/image?id=95388&rendTypeId=34

19. Cross-Pollination by man http://hordeum.oscs.montana.edu/home/documents/methods1.htm

20. Mendel Studied Characteristics • A characteristic is a feature that has different forms in a population. Examples: hair color, eye color • The different forms of a characteristic is called a trait. Examples: red hair, blue eyes • Mendel used peas to mix and match traits of different characteristics.

21. Mendel’s First Experiments • Mendel crossed true breeding pea plants to study 7 characteristics • The offspring from the cross of 2 true breeding plants are called the first generation plants • In his experiment, one trait was always present and one trait seemed to disappear

22. Dominant and Recessive Traits • Dominant Trait – the trait that was always present in the first generation • Recessive Trait - all other traits seem to fade into the background, and are not shown in the first generation • Dominant and Recessive traits appear in all organisms

23. Mendel’s Second Experiment • Mendel allowed first generation plants to self-pollinate • The recessive trait reappearedin the second generation. • He did the same with each of the other 6 characteristics, in each case the recessive trait reappeared.

24. Ratio’s in Mendel’s Experiments • Mendel tried to figure out the ratio of dominant traits to recessive traits • A ratio is a relationship between 2 numbers that is often expressed as a fraction (not always – 3:1 or 3 to 1)

25. Mendel - Gone But Not Forgotten • Each pea plant has 2 sets of instructions for each characteristic • Each parent would donate 1 set of instructions • Mendel published his results but it was 30 years after his death before he was recognized for his work.

26. Traits and Inheritance • Gene: a set of instructions for a trait. • Gene is made up of 2 or more parts called alleles. One comes from the biological mother and one from the biological father. • Allele: different forms of a gene. • Dominant alleles are written with a capital letter. • Recessive alleles are written with a lower case letter.

27. Genes • Chromosomes are in the nucleus of the cell. • Chromosomes are made up of DNA. • Genes are a section of DNA • Alleles are part of a gene given to an organism from each parent.

28. Human Chromosomes

29. Female Chromosomes Matched

30. Male Chromosomes Matched

31. Alleles

32. Phenotype • Is an organism’s appearance • Written in words • Example: purple or white flowers • Example: brown eyes, blue eyes, hazel eyes. Green eyes

33. Genotype • Letters that represent the alleles for each trait. • Dominant traits are written with capital letters • Recessive traits are written with lower case letters. • Homozygous: an organism with either 2 Dominant or 2 Recessive allele. True breed. • Example: TT (Tall plant) tt (short plant) • Heterozygous: an organism with one Dominant allele and one Recessive allele. • Example: Tt (Tall plants)

34. Punnett Square • Used to calculate the possible outcomes of a genetic cross. • The alleles from both parents are placed