Patterns of Inheritance - Patterns of Inheritance Heredity...

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Patterns of Inheritance: Heredity is the transmission of traits from one generation to the next. Genetics is the scientific study of heredity. Gregor Mendel ~ father of genetics A heritable feature that varies among individuals, such as flower color, is called a characteristic . Each variant for a characteristic, such as purple or white flowers, is a trait . True-breeding varieties result when self-fertilization produces offspring all identical to the parent. The offspring of two different varieties are hybrids . The cross-fertilization is a hybridization, or genetic cross . True-breeding parental plants are the P generation . Hybrid offspring are the F 1 generation . A cross of F 1 plants produces an F 2 generation . A cross between two individuals differing in a single character is a monohybrid cross . Mendel performed a monohybrid cross between a plant with purple flowers and a plant with white flowers. The F 1 generation produced all plants with purple flowers. A cross of F 1 plants with each other produced an F 2 generation with ¾ purple and ¼ white flowers. Mendel developed four hypotheses, described below using modern terminology. 1. Alleles are alternative versions of genes that account for variations in inherited characters. 2. For each characteristic, an organism inherits two alleles, one from each parent. The alleles can be the same or different. A homozygous genotype has identical alleles. A heterozygous genotype has two different alleles. 3. If the alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele. The other has no noticeable effect on the organism’s appearance and is called the recessive allele. The phenotype is the appearance or expression of a trait. The genotype is the genetic makeup of a trait. The same phenotype may be determined by more than one genotype.
4. A sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes. This statement is called the

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