2Gregor MendelYoung priest that worked in the garden at a monastery in Vienna.Considered the “Father of Genetics”Observed traits in hundreds of pea plants.
3Mendel’s Work - Vocabulary TraitsPhysical characteristics of organisimsHeredityPassing of traits from parent to offspringGeneticsScientific study of heredity
4Mendel’s Peas Why was Gregor Mendel lucky he chose peas to study? Many traits exist only in two formsPeas produce many offspring in one generation.
5How did Mendel make his crosses? White PlantPurple Plant
6True Breeding (Purebred) Plant Mendel’s ExperimentsTrue Breeding (Purebred) PlantOne that always produces offspring with the same form of a trait as the parenti.e. purebred short plants will only produce short offspring.
7Purebred purple plants will only produce purple plants X
8White flower would mean the parents are not purebred X
9Mendel’s ExperimentsMendel crossed plants with opposite forms of a traiti.e. purple flowers crossed with white flowersLook at Figure 3 on page 152Explain why all offspring are purple in the first generation (F1)What happens in the second generation (F2)
10Mendel’s ExperimentsMendel studied flower color followed by six other “opposite” traits.Look at table 1 on page 154.What do you notice about the ratio of traits in the second generation (F2)
12Genes and Alleles Genes Alleles Factors that control traits Different forms of a geneOne allele is inherited from each parent.Alleles can be dominant or recessive
13Dominant and Recessive Alleles Dominant alleleAlways seen if presentIndicated by a capitol letter (T)Recessive alleleMasked or hidden if dominant allele is presentIndicated by a lower case letter (t)
14Hybrid vs Purebred Hybrid Purebred Organism has two different alleles for the trait – one dominant and one recessive.PurebredOrganism has two identical alleles for a trait – two recessive OR two dominant.
15Alleles are represented with capitol and lower case letters. T = Tall allele (dominant)t = Short allele (recessive)PurebredsTT – two dominant alleles – plants will be talltt – two recessive alleles – plants will be shortHybridTt – one dominat allele and one recessive allele – plants will be tall.
16Phenotypes 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
17Homozygous 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
18Probability Probability Example: coin toss The likelihood that a particular event will occurExample: coin toss
19Punnett Squares Punnett Squares chart that shows all possible combinations of alleles that can result from a genetic cross. Used to determine the probability of a particular outcome.
20Using a punnett square Tt t T T Tt t TT Tt Tt tt Tall Tall Tall Short
21CodominanceCodominance – alleles are neither dominant or recessive therefore both alleles are expressed in the offspring
22CodominanceThe heterozygous offspring will express (show) both phenotypes
23What is the rabbit’s phenotype for fur color? _________ Consider a rabbit with black fur and the allele combination (Bb).What is the rabbit’s phenotype for fur color? _________What is the rabbit’s genotype for fur color? __________Is the rabbit heterozygous or homozygous for the fur color trait? _______________If black is dominant over white, what genotype would produce a white rabbit? _______If fur color in rabbits was a codominant trait instead of dominant/recessive trait, what color fur would the (Bb) rabbit have? ________________Black(Bb)heterozygous(bb)White and black23