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Mendelian Genetics
12/5/2018
Mendelelian Genetics
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2. Responsible for the Laws governing Inheritance of Traits
Mendelian Genetics
12/5/2018
Gregor Mendel ( )
Responsible for the Laws governing Inheritance of Traits
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Mendelian Genetics
12/5/2018
Gregor Johann Mendel
Austrian monk
Studied the inheritance of traits in pea plants
Developed the laws of inheritance
Mendel's work was not recognized until the turn of the 20th century
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Mendelian Genetics
12/5/2018
Gregor Johann Mendel
Between 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants
He found that the plants' offspring retained traits of the parents
Called the “Father of Genetics"
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5. Site of Gregor Mendel’s experimental garden in the Czech Republic
Mendelian Genetics
12/5/2018
Site of Gregor Mendel’s experimental garden in the Czech Republic
Fig. 5.co
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Mendelian Genetics
12/5/2018
Genetic Terminology
Trait - any characteristic that can be passed from parent to offspring
Heredity - passing of traits from parent to offspring
Genetics - study of heredity
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7. Particulate Inheritance
Mendelian Genetics
12/5/2018
Particulate Inheritance
Mendel stated that physical traits are inherited as “particles”
Mendel did not know that the “particles” were actually Chromosomes & DNA
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Traits are created by genes, which are small sections of DNA that code for a protein. Traits result from proteins!
Genes are found on chromosomes.
Each chromosome can have thousands of genes
Sexual organisms have 2 sets ofchromosomes—one set from each parent.
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Mendelian Genetics
12/5/2018
Genotypes
Alleles – different forms of a gene (some dominant & some recessive)
Homozygous genotype - gene combination involving 2 dominant or 2 recessive alleles (e.g. RR or rr); also called pure 
Heterozygous genotype - gene combination of one dominant & one recessive allele    (e.g. Rr); also called hybrid
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Mendelian Genetics
12/5/2018
Designer “Genes”
Dominant - stronger of two genes expressed in the hybrid; represented by a capital letter (R)
Recessive - gene that shows up less often in a cross; represented by a lowercase letter (r)
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Mendelian Genetics
12/5/2018
More Terminology
Genotype - allele combination for a trait (e.g. RR, Rr, rr)
Phenotype - the physical feature resulting from a genotype (e.g. red, white)
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13. Mendelian Inheritance
Each person has 2 copies of every gene—one copy from mom and a second copy from dad. These copies may come in different variations, known as alleles, that express different versions of a trait.
For example, 2 alleles in the gene for freckles are inherited from mom and dad:
allele from mom = has freckles (F)
allele from dad = no freckles (f)
child has the inherited gene pair of alleles, Ff (F allele from mom and f allele from dad).
Review with students the term “allele” (a variant form of a gene) and help students understand that each gene has a pair or two alleles—one allele from mom and the other from dad.

14. Mendel’s Laws
Law of Segregation- During meiosis, the alleles for each gene separate from each other so that each gamete carries only one allele.
Law of Independent Assortment- Genes for different traits are inherited separately (unless located near each other on the same chromosome)
Law of Dominance- Some alleles are dominant while others are recessive; the dominant effect will be shown over recessive
Review key concepts of Mendelian Inheritance with students. For #3, ask students what situations may call for an unobservable trait to be passed from parents to children. Students may be able to apply their understanding of dominant and recessive traits where parents with both dominant and recessive traits only show dominant traits while being able to pass their recessive traits to the next generation.