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Important Vocabulary Heredity Allele Genetics Hybrid Dominant Recessive Punnett square Genotype Phenotype Homozygous Heterozygous
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Inheriting Traits Heredity: the passing of traits to offspring An organism is a collection of traits inherited from its parent or parents
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What is genetics? Alleles: different forms of a trait that make up a gene pair When a pair of chromosomes separate during meiosis, the alleles of a gene pair also separate into different sex cells As a result, every sex cell has one allele for each trait Genetics: the study of how traits are inherited through the interactions of alleles http://glencoe.mcgraw- hill.com/sites/0078693918/student_view0/concepts_in_motion.ht ml# (Click on Meiosis and Fertilization)
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Mendel- The Father of Genetics Gregor Mendel Austrian monk who studied math and science Became the gardener at a monastery Predicted the types of flowers and fruits that would result from crossbreeding two plants Began experimenting with peas in 1856 Shared results 8 years later with other scientists http://science.discovery.com/tv- shows/greatest-discoveries/videos/100- greatest-discoveries-shorts-genetics.htm
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Mendel- The Father of Genetics Mendel was the first scientist to trace one trait through several generations
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Genetics in a Garden Each time Mendel studied a plant, he crossed two plants with different expressions of the trait He found that the new plants all looked like one of the two parents These new plants were called “hybrids” Hybrid: receives different genetic information, or different alleles, for a trait from each parent Purebred: organism that always produces the same traits generation after generation
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Dominant and Recessive Factors Mendel found that tall plants that were crossed with short plants produced seeds that were all tall plants Mendel called the tall form the “dominant” factor Dominant: dominates, or covers up, another allele Dominant alleles are written in capital letters Ex. B = purple flower Recessive: allele that seems to “disappear” or is covered up Recessive alleles are written in lower case letters Ex. b = white flower
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Using Probability to Make Predictions Mendel dealt with probabilities His results were more accurate because he worked with many plants– about 30,000 pea plants! This increased Mendel’s chances of seeing a repeatable pattern Punnett square: tool used to predict the results in Mendelian genetics
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Punnett Squares In Punnett squares, letters symbolize alleles Remember, capital letters represent dominant alleles and lowercase letters represent recessive alleles The letters form a code for the genetic makeup an organism Genotype: genetic make up of an organism (BB, Bb, bb) Phenotype: the way an organism looks and behaves based on their genotype (purple flower or white flower)
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Alleles Determine Traits Most cells in your body have at least two alleles for every trait Located on chromosomes within each cell’s nucleus Homozygous: an organism that has two alleles that are the same Example: BB or bb Heterozygous: an organism that has two different alleles Example: Bb
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Making a Punnett Square Make a grid like this one: One parent’s alleles are placed on the top, second parent’s alleles place along the side like this (one letter per column/row): Each square is filled in with one allele donated by each parent. Make sure the capital (or dominant) allele is placed before the lowercase (or recessive) allele. In this Punnett square, the probability of each genotype is: BB: 25% or ¼ Bb: 50% or ½ bb: 25% or 1/4 Bb B b Bb BBbBbB bbBbBb Bb BBBbBb bBbBbb
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Principles of Heredity It took Mendel years of detailed observation, careful analysis, and repeated experimentation to conclude his ideas of heredity. The following tables sums them up in three principles:
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Video Links http://www.youtube.com/watch?v=xc2wbIDfO7E http://www.youtube.com/watch?v=xc2wbIDfO7E http://learn.genetics.utah.edu/content/begin/traits/tour_t rait.html http://learn.genetics.utah.edu/content/begin/traits/tour_t rait.html http://learn.genetics.utah.edu/content/begin/traits/tour_ heredity.html http://learn.genetics.utah.edu/content/begin/traits/tour_ heredity.html
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Resources Florida Science Grade 8 Glencoe Science & McGraw Hill Publishing Google Images
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