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What was Hippocrates explanation of inheritance?
Pangenesis: particles called pangenes travel from each part of an organism's body to the eggs or sperm and then are passed to the next generation.
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Heredity
The transmission of traits from one generation to the next.
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Genetics
- The scientific study of heredity.
- Began in the 1860's.
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What did Mendel call genes?
"Heritable factors"
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Character
A heritable factor "gene" that varies among individuals, such as flower color.
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Trait
Each variant for a character, such as purple or white flowers.
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Self-fertilize
Sperm-carrying pollen grains released from the stamens land on the egg-containing carpel of the same flower.
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Cross-fertilization
Fertilization of one plant by pollen from a different plant.
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True-breeding
Varieties for which self-fertilization produced offspring all identical to the parent.
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Hybrids
- The offspring of two different varieties.
- The cross-fertilization itself is referred to as hybridization or simply a genetic cross.
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P Generation
- The true-breeding parental plants.
- "P" for parental.
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F1 Generation
- The hybrid offspring.
- "F" for filial, from the Latin word for "son".
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F2 Generation
When F1 plants self-fertilize or fertilize each other.
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Monohybrid cross
The parent plants differ in only one character - flower color.
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Alleles
- The alternative versions of a gene.
- Example: the gene for flower color in pea plants exists in two versions: one for purple and the other for white.
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Homozygous
- Two indentical allels for a gene.
- Example: BB, PP
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Heterozygous
- Two different allels for a gene.
- Example: Bb, Pp
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Dominant
- When one allele determines the organism's appearance.
- We use uppercase letters to represent dominant alleles.
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Recessive
- An allele that has no noticeable effect on the organism's appearance.
- We use lowercase letters to represent recessive alleles.
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Mendel's Law of Segregation
- A sperm or egg carries only one allele for each inherited character because allele pairs seperate (segregate) from each other during the production of gametes.
- When sperm and egg unite at fertilization, each contributes its allele, restoring the paired condition in the offspring.
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Punnett Square
A table that shows the four possible combinations of alleles that could occur when gametes combine.
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Phenotype
The expressed (physical) traits of an organism.
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Genotype
The genetic makeup of an organism.
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