2 Gregor MendelYoung priest that worked in the garden at a monastery in Vienna.Considered the “Father of Genetics”
3 Mendel’s Work - Vocabulary TraitsA physical characteristic that an organism can pass on to its offspring through its genes.HeredityPassing of traits from parent to offspringGeneticsScientific study of heredity
4 Mendel’s ExperimentsWhat type of plant did Gregor Mendel use for most of his studies?The Pea Plant
5 Mendel’s Peas Peas are good plants to use for genetic studies because: Many traits exist only in two forms (i.e. tall and short) And….Peas produce many offspring in one generation making it is easy to collect and analyze large amounts of data.
6 How did Mendel make his crosses? – Basics First.. Pea plants reproduce by the same method as most plants. The pollen (male reproductive part of a plant) is transferred to the pistil (female reproductive part of a plant) and the ovary is fertilized producing a fruit (baby plant). Pollen can be transferred by many methods such as wind, water and bees.Pollen
7 How did Mendel make his crosses? Mendel transferred the pollen from one plant to the pistil of another plant. For example, pollen from a tall plant was used to fertilize the pistil of a short plant essentially making the father plant tall, and the mother plant short.In order to prevent self pollination, Mendel removed the pollen producing parts of the short plantTall PlantShort Plant
8 Mendel’s Experiments Purebred Plant One that always produces offspring with the same form of a trait as the parentFor example….
9 Purebred pink plants will always produce pink plants XIf a white flower is produced by two pink flowers, the parents CANNOT be purebredX
10 Mendel’s ExperimentsHow did Mendel make sure he had purebred plants to make his crosses?By allowing pea plants of one particular trait self pollinate for several generations.
11 Mendel’s ExperimentsIn Mendel’s first experiment he crossed PUREBRED TALL plants with PUREBRED SHORT plants.These plants were called the parental generation or the P generationThe offspring of this cross was called the first filial generation or the F1 generation.After the F1 plants self pollinated they produced the second filial generation or the F2 generation
12 Mendel’s ExperimentsWhat types of plants (Short/Tall) did Mendel observe in the F1 generation?All Tall plantsWhat types of plants (Short/Tall) did Mendel observe in the F2 generation?A mix of short and tall plants.The ratio of tall to short was 3 to 1 or 75% tall and 25% short.
13 Mendel’s ExperimentsWhat conclusions did Mendel arrive at from his experiments with peas?Some sort of “factor” controls the inheritance of traits in pea plants.These “factors” exist in pairs with the female contributing one factor and the male contributing the other.One factor can “mask” the presence of the other.
14 Mendel’s ExperimentsWhat modern words do we now use for Mendel’s discoveries.Mendel said “factors.” Today scientist call these factors that control traits genes.Mendel concluded that these genetic factors exist in pairs. Today we call these two forms of a gene alleles.Mendel realized that one factor in the pair can mask the other. Today we know these as dominant alleles and recessive alleles.
15 Mendel’s Work - Vocabulary Dominant AlleleOne whose trait always shows up in the organism when the allele is present.Recessive AlleleOne that is masked or covered up when the dominant allele is present. Recessive traits only show up when two recessive alleles are present.HybridAn organism that has two different alleles for a trait.
16 Mendel’s ExperimentsOther “opposite” traits that Mendel studied (Figure 3 on page 83).Seed Shape – round (dominant) wrinkled (recessive)Seed Color – yellow (dominant) green (recessive)Seed Coat Color – gray (dominant) white (recessive)Pod Shape – smooth (dominant) pinched (recessive)Pod Color– green (dominant) yellow (recessive)Flower Position– side (dominant) end (recessive)
17 Dominant and Recessive Alleles In modern genetics scientist represent the dominant allele with a capitol letter and the recessive allele with the lower case version of the same letter.The same letter is used for the dominant and the recessive allele. For example….Tall plants would be represented by TShort plants would be represented by t
18 Dominant and Recessive Alleles Assigning the letter to the allele is random. However scientist often use the dominant trait. Examples…Seed color: Yellow Y Green ySeed coat color: Gray G White gSeed shape: Round R Wrinkled r
19 Dominant and Recessive Alleles Genes exist in pairs and are made up of two alleles. One allele comes from mom and the other allele comes from dad. Assign the following allele combinations.A plant that inherits two alleles for Yellow seed color YYA plant that inherits one allele for Yellow seed color and one allele green seed color YyA plant that inherits two alleles for wrinkled seeds rrA plant that inherits one allele for round seed shape and one allele wrinkled seed shape RrA plant that inherits two alleles gray seed coat color GG
20 Phenotypes and Genotypes Physical appearance or visible traitExample is flower color, stem height etc.GenotypeThe genetic makeup or allele combinationExamples are TT or TtGenotypes determine phenotypes
21 Phenotypes and Genotypes Figure 9 on the top of page 92Phenotypes are Tall and ShortGenotypes for tall plants are TT and TtOnly genotype that can produce a short plant is tt
22 Homozygous and Heterozygous An organism that has two identical alleles for a traitTT – homozygous dominanttt – homozygous recessiveHeterozygousAn organism that has two different alleles for a traitTt – heterozygous – will show the dominant trait
23 Homozygous and Heterozygous What term did Mendel use that means the same thing as heterozygous?Hybrid