Introduction to Genetics Ch. 11

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Genetics The scientific study of heredity

Gregor Mendel Father of modern genetics Combined plant breeding, statistics, careful record keeping

Mendel studied pea plants traits (characteristics)

Genetic Information Gene – basic unit of genetic information Allele – one form of a gene

Principle of Dominance Some alleles are dominant and others are recessive

Dominant vs. Recessive Dominant alleles express a trait. (capital letter) Recessive alleles are only visible when paired with another recessive allele. (lower case letter)

Segregation Gamete Separation of alleles during gamete formation Sex cells

Punnett Square Diagram used to predict and compare variations resulting from a genetic cross

Homozygous vs. Heterozygous Homozygous - having two dominant or two recessive alleles. (BB or bb) Heterozygous - having both a dominant and recessive allele. (Bb)

Genotypes Phenotypes Genotype - genetic make up Phenotype – physical characteristics

Genotypes Phenotypes (example) genotypes phenotypes

Hybrid Offspring of crosses between parents with different traits

Principle of Independent Assortment Genes for different traits can segregate independently during the formation of gametes. Example: genes for seed shape segregate independently of those for seed color

Incomplete Dominance One allele is not completely dominant over another

Incomplete Dominance A flower has genes for white petals (w) and red petals (r). When you mix white flowers with red flowers you get pink flowers. How is this possible? The w gene does not dominate over the r gene and vice versa. Both genes express themselves equally so you get a pink color in the petals. ww rwr r

Codominance Both alleles contribute to the phenotype

Polygenetic Traits Traits controlled by two or more genes

Meiosis reproduction of gametes (Similar to mitosis, but there are 2 divisions, ending with ½ the number of chromosomes of the parent cell.)

Diploid vs. Haploid Diploid – contains both sets of homologous chromosomes Haploid – contains a single set of chromosomes

Crossing-over is the process in which homologous chromosomes exchange portions of their chromatids during meiosis.

Gene Map Diagram showing the relative locations of each known gene on a particular chromosome