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Chapter 14 (Useful Genetic Vocabulary (An organism that has a pair of…
Chapter 14
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character
A heritable feature that varies among individuals, such as flower color.
trait
Each variant for a character, such as purple or white color for flowers
Mendel chose to track only those characters that occurred in two distinct, alternative forms, such as purple or white flower color.
true-breeding: he also made sure that he started his experiments with varieties that were true-breeding ----that is, over many generations of self-pollination, these plants had produced only the same variety as the parent plant
for example: a plant with purple flowers is true-breeding if the seeds produced by self-pollination in successive generations all give rise to plants that also have purple flowers
Hybridization
In a typical breeding experiment, Mendel cross-pollinated toe contrasting, true-breeding pea varieties- for example, purple-flowered plants and white-flowered plants. This mating, or crossing, of two true-breeding varieties
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Around 1857, Mendel began breeding garden peas in the abbey garden to study inheritance
For example, one variety has purple flowers, while another variety has white flowers.
Mendel's Model
Mendel developed a model to explain the 3:1 inheritance pattern that he consistently observed among the F2 offspring in his pea experiments.
alleles
The gene for flower color in pea plants, for example, exists in two versions, one for purple flowers and the other for white flowers. These alternative versions of a gene
dominant allele
If the two alleles at a local differ, then it determines the organism's appearance
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law of segregation
The fourth and final part of Mendel's model, the law of segregation , states that the two alleles for a heritable character segregate during gamete formation and end up in different gametes.
Punnett square
a handy diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup
Physicist Christian Doppler was one who encouraged his students learn science through experimentation and trained Mendel to use mathematics to help explain natural phenomena
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Polygenic Inheritance
multifactorial
meaning that many factors, both genetic and environmental, collectively influence phenotype
quantitative characters
many characters, such as human skin color and height, are not one of two discrete characters, but instead vary in the population in gradations along a continuum.
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Mendel studied characters that could be classified on an either-or basis, such as purple versus white flower color
fetal testing
amniocentesis
one of the tests that can be done to determine whether the developing fetus has Tay-sachs disease, which can be performed starting at the 15th week of pregnancy
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medical scientist have also developed methods for isolating fetal cells, or even fetal DNA, that have escaped into the mother's blood