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a. Explanation of heredity most widely in favor= __
blending hypothesis
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Explain the blending hypothesis
- i. Genetic material contributed by two parents mixes in manner similar to paint
- 1. Predicts that freely mating population will give rise to uniform population of individuals
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particulate hypothesis
- i. Gene idea
- ii. Parents pass on discrete heritable units—genes—that retain their separate identities in offspring
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a. __ documented __mechanism for inheritance
b. Use of Garden Peas
i. Encouraged by strong professors to become scientists
1. Christian Doppler: experimentation/ trained Mendel to use math to help explain natural phenomena
2. Franz Unger: aroused Mendel’s interest in causes of variation in plants
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i. Began breeding garden peas to study __
Why peas?
- inheritance
- 1. Large variety
- 2. Short generation time and large number of offspring from each mating
- 3. Strict control of mating
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1. Large variety
a. Hereditable feature that varies among individuals= __
b. Variant of character= __
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Strict control of __
a. Reproductive organs of pea plant in flowers, and each pea flower has both __ and __
b. Usually __
i. To __, he removed immature stamens before pollination could occur and dusted pollen from another plant onto altered flowers
1. Resulting zygote: developed into plant embryo encased in seed (pea)
- mating
- pollen-producing organs (stamens) and egg-bearing organs (carpels)
- self-fertilize
- cross-fertilize
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i. Mendel only tracked characters that occurred in __ different forms
1. Ex: purple or white flowers, no intermediate
ii. Also, used __ plants
1. What are they?
- two
- true-breeding
- varieties that, over many generations of self-pollination, produced same variety as parent cell
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i. Typical breeding Experiment
1. Cross-pollinated two contrasting, __pea varieties
a. __, or crossing, of two true-breeding parents is __
i. Parents: __ generation
1. Hybrid offspring:__
a. Their hybrid offspring
i. __
- true-breeding
- Mating
- hybridization
- P
- F1
- F2
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ii. Mendel’s quantitative analysis of the F2 plants from thousands of genetic crosses allowed him to deduce two fundamental principles of heredity:
1. __ and __
Law of segregation and law of independent assortment
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b. Law of Segregation
i. All F1 offspring had what color flowers?
1. White appeared in __generation
2. __ ratio in F2 ratio
ii. Heritable factor for white flowers did not disappear in F1 plants, but was __, when purple-flower factor present
1. Purple flower: __
2. White: __
- second, F2,
- 3:1
- just as purple as purple-flowered parents
- hidden or masked
- dominant
- recessive
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iii. Mendel’s model
1. __related concepts making up his model, the fourth which is the__
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What are his related concepts?
- a. Alternative versions of genes account for variations in inherited characters
- i. Alternative versions= alleles
- b. For each character, an organism inherits two copies of a gene, one from each parent
- c. If two alleles at locus differ, the dominant allele determines the organism’s appearance; the recessive has no noticeable effect on the organism’s appearance
- d. Law of Segregation: two alleles for a heritable character segregate during gamete formation and end up in different gametes
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i. Genetic __represented __in diploid cell, once on each __of a specific pair of chromosomes
1. Two __at locus may be identical or different
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iv. __: handy diagrammatic device for predicting allele composition of offspring form a cross between individuals of known genetic makeup
1. Capital letter: __
2. Lowercase: __
- Punnett Square
- dominant
- recessive
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1. Organism with pair of identical alleles for character: __
a. Parental generation, the purple plea plant was __for dominant (PP) allele, while white is __for recessive (pp) allele
- homozygous
- homozygous
- homozygous
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2. Organism with two different alleles for gene is __
a. Produce gametes with different alleles, so not __
3. Because of this, organism’s traits don’t always reveal genetic composition
a. Appearance and physiological traits: __
b. Genetic makeup: __
- heterozygous
- true-breeders
- phenotype
- genotype
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i. Test Cross
- i. Test Cross
- 1. If we have a mystery pea plant with purple flowers and want to know whether it is homo or heterozygous, we cross it with a white plant, which will make only gametes with recessive allele
- a. Allele in gamete contributed by mystery plant will determine appearance
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Results of Test Cross
- i. If homozygous dominant, it will result in an all-purple F1 generation
- ii. If heterozygous, the offspring will be 1:1 ratio, both purple and white
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1. All F1 progeny produced in crosses of true-breeding parents were __, meaning they were heterozygous for one particular character being followed= __
2. Mendel followed two characters at same time= __= __
- monohybrids
- monohybrid cross
- dihydrbids
- dihybrid cross
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3. Will separate characters stay together?
4. In F2 offspring, the hybrids do not transmit alleles in same combinations in which the alleles were inherited from P generation
a. If this did occur, what would it result in?
- not always
- This would result in the F1 hybrids producing only two classes of gametes= dependent assortment= rejected
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5. Two pairs of alleles segregate __of each other
a. Genes packaged into gametes in all possible allelic combinations
i. __ ratio for dihybrid cross
1. 16 probable ways to combine
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Law of Independent Assortment
each pair of alleles segregates independently of each other pair of alleles during gamete formation
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The Law of Independent Assortment applies only to __
genes on different chromosomes—on nonhomologous chromosomes—or very far apart on same chromosome
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