Download Mendelian Genetics

Mendelian Genetics What is Genetics? •
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It is the ____________________________________________________ in organisms. _______________________________________ of a living thing by controlling the formation of an organism's proteins. Each cell contains ____________________________________, one on the maternal chromosome and one on the paternal chromosome. o Remember: all cells (except gametes) are diploid, meaning they exist as a pair Genes: •
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The 2 genes may be of the same form or they may be of different forms. o These _______________________________________________________________of each trait. § For example: A gene for plant height might occur in a tall form or a short form. o The __________________________________________________________________. o The ______________________________________________________during the process of gamete formation (meiosis II) Since organisms receive one gene for a chromosome pair from each parent, organisms Who was Gregor Mendel? •
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Johann Mendel was born in 1822 in an area of Austria that is now part of the Czech Republic. In 1843, he became a monk and took the name “Gregor”. While at the monastery, he was the caretaker of the garden. In 1851, he went to the University of Vienna to study biology and math. He ______________________________________________________________________________ in pea plants. What did Mendel Study? •
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The popular theory of inheritance before Mendel came along was “Blending”, which stated that offspring are a mix of their parents’ traits (i.e. tall x short = medium) Mendel’s observations went against this theory. His pea plants were either identical to their parents, or completely different, not in-­‐between. He studied seven characteristics of pea plants: flower color & position, pod shape & color, stem length, and seed shape & color. Mendel’s Methods: •
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Mendel started his experiment with true-­‐breeding pea plants o Plants that always produced offspring identical to themselves Pea plants are self-­‐pollinating, meaning the pollen from a flower can fertilize itself. •
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Mendel controlled the pollination of the plants by removing the anthers (male) from the flower. Then, he carefully transferred pollen from other flowers on the stigma (female part) of the “neutered” flowers to cause cross-­‐pollination. Mendel’s First Experiment: •
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Mendel called the true-­‐breeding parent ___________________________________________________. He crossed true-­‐breeding purple flowered pea plants with true-­‐breeding white flowered plants. All of the offspring had purple flowers! He called these ______________________________________ (for first filial). These plants were hybrids. When he let the F1 offspring self-­‐pollinate, about 75% of the offspring had purple flowers, but 25% had white flowers. He called these offspring the _________________________________. Mendel’s Results & Analysis: •
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Mendel proposed that _________________________________________________________that was passed from parents to offspring. o Today we call that heritable factor a __________________ Mendel wanted to know why the white flowered plants “disappeared” in the F1 generation, but then reappeared in the F2 generation. He also wondered why he always observed a 3:1 ratio in the F2 generation of purple:white flowers. _________________________________________________________for pod shape & color; seed shape & color; always observing the same results and ratios. Mendel’s Law of Dominance: •
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Law states that there are _____________________________________________________________ ____________________________________. States that __________________________________________________________________ o An organism with a dominant allele for a particular trait will always have that trait expressed in the organisms. o An organisms with a recessive allele for a particular trait will only have that trait expressed when the dominant allele is not present. Homozygous: •
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When an organism has _______________________________________for a particular trait that organisms is said to be ________________________for that trait o The paternal chromosome and the maternal chromosome have the same form of the gene. o They are ______________________________________________________ Examples: (For blue color, B = blue and b = pink) o BB o bb Heterozygous: •
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When an organism has __________________________________________for a particular trait that organism is said to be heterozygous for that trait o The paternal chromosome and the maternal chromosome have different forms of the gene; ___________________________________________________ Example: (color, B = blue and b=pink) o Bb (blue) Genotype: •
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Genotype: o The genetic make-­‐up of an organism reveals the ____________________________________ _____________________for a particular trait. The genotype for a particular trait is ___________________________________________________. o The ___________________________representing the dominant gene. o The _________________________________representing the recessive gene. Examples: o TT – represents a homozygous dominant genotype o tt – represents a homozygous recessive genotype o Tt – represents a heterozygous genotype Phenotype: •
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Phenotype: o The _______________________________________of an organism is a description of the way that a trait is expressed in the organism Organism with the genotype of BB or Bb would have a phenotype of black. Organism with the genotype of bb would have a phenotype of white. Law of Segregation: •
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The law of segregation ________________________________________________________________ Each gamete receives one of the two alleles that the parent carries for each trait. o Each gamete has the same chance of receiving either one of the alleles for each trait. During fertilization (when the egg and sperm unite), _________________________________________ ________________________________________________. Law of Independent Assortment: •
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The law of independent assortment states that the __________________________________________ ___________________________________________________________________________ o Genes on separate chromosomes separate independently during meiosis This law ________________________________________________ unless the genes are linked. o In this case, the genes that do not independently segregate during gamete formation, usually because they are in close proximity on the same chromosome. Punnett Squares: •
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The principles of Mendelian genetics can be used to _________________________________________ ____________________________________. A punnett square can be used to ______________________________________________________ that result from different parental allele combinations that are independently assorted. A monohybrid cross examines the __________________________________________. The cross could be any of the following: o homozygous-­‐homozygous o heterozygous – heterozygous o Heterozygous -­‐ homozygous Example: o Represent the probable outcome of two heterozygous parents with the trait for height: T = dominant (tall) and t = recessive (short) Tt x Tt o The _______________________________________and the _____________________________ o The square shows the following possible ________________________: § _________ratio (______%) for two dominant alleles § _________ ration (______%) for two recessive alleles § _________or 1:2 ratio (______%) for one dominant and one recessive allele o The square shows the following _____________________are possible: § ______ratio (______%) to express the tall trait § ______ratio (______%) to express the short trait Remember that only ________________________________________________for the offspring o Not all 4 options are made into one offspring o A punnett square just gives you ____________________________________for the offspring Practice problem: o What are the potential genotypic and phenotypic outcomes if two heterozygous parents for body color are crossed? § Male parent = blue o Female parent = red o Blue is dominant over red A ___________________________examines the inheritance of ________________________________ Example: o Homozygous parents for shape and color are crossed o R = dominant round; r = recessive wrinkled; Y = dominant yellow; y = recessive green o rryy x RRYY o The parents are the F1 generation and the offspring are the F2 generation Dihybrid Example Continued… All of the offspring for this generation would predictably have the same genotype, heterozygous for both traits (RrYy) •
All of the offspring for this generation would predictably have the same phenotype, round and yellow (16/16 will be round and yellow