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)

5

6

7

8

9

10 A Wild Strawberry Flower Anther Filament Pistil Female Reproduction organ Male Reproduction organ 1 2 3

11 na.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 (Bee on flower) (Importance of Honey Bees in pollination) The Pollination Song l

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 owers/pollin ators/images /selfpollinati on.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 s/wildflowers/polli nators/images/xpol lination_ani.gif

17

18 Cross-pollination

19 Cross-Pollination by man cs.montana.edu/h ome/documents/m ethods1.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 reappeared in 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