Genetics 3.4 Inheritance. Mendel and the principles of inheritance Gregor Mendel!/people/gregor- mendel-39282!/people/gregor-

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Genetics3.4 InheritanceMendel and the principles of inheritanceGregor Mendel!/people/gregor-mendel-39282Worked with pea plants.Carefully crossed varieties of peas by transferring pollen. Grew the resulting pea seeds.Repeated with many plants.Examined 7 different pairs of characters.

Mendel and the principles of inheritancePioneer of research methods in biology

Nature of science:What aspects of his research were good science?Model organism: clear characteristics that can be easily followed. And multiple characteristics allowed the conclusion that his results were not isolated to one characteristic.Quantitative: permits statistical tests of significanceLarge number of replicatesMultiple samples during individual experimentsAnd whole experiments


Blended inheritanceMany early theories involved blended inheritance:See page text 170 for Mendels results

Mendel's Laws of InheritanceLaw of Segregation: During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.Law of Independent Assortment: Genes for different traits can segregate independently during the formation of gametes.Law of Dominance: Some alleles are dominant while others are recessive; an organism with at least one dominant allele will display the effect of the dominant allele.Segregation of AllelesDuring meiosis, a diploid nucleus divides twice to produce 4 haploid nuclei.Segregation: The separation of alleles into different nuclei.If 2 copies of one allele of a gene were present (ie PP), each haploid nuclei will receive a copy of this gene. Every gamete gets a P.If two different alleles were present (ie Pp), each haploid nucleus will receive either one of the alleles or the other.50% of the haploid cells will receive P & 50% will receive pDominant, recessive and co-dominantDominant vs recessive: one allele is expressed over the other at the same locus.Co-dominant: pairs of alleles both have an effect.

Genotype vs PhenotypeGenotype: the genetic makeup of a cell, an organism, or an individual usually with reference to a specific characteristic under consideration. Phenotype: The outward appearance of an organism; the expression of a genotype. Depends on which genes are dominant and on the interaction between genes and environment., such as hair or eye color.

Homozygous vs HeterozygousHomozygous: describes a genotype consisting of two identical alleles at a given locusHeterozygous: describes a genotype consisting of two different alleles at a locus

Punnett Grids