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22 Cards in this Set
- Front
- Back
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Blended Inheritance Model |
hereditary material mixed in offspring.once mixed, it can’t be separated.
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Inheritance of acquired characteristicsc |
parents modify their traits based on usemodified traits passed on to offspring
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Particulate theory of heredity |
-Created by Gregor Mendel -parents transmit heritable factors ("genes") that remaindistinct from one generation to the next. |
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Mendel's experimentation |
-Crossed plants that differed from all but one trait in order to witness change in that one trait/control genotypes |
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Mendel's Principles of Segregation |
Traits of diploid organisms determined by combination ofgenes on homologous chromosomesThe two alleles for each character are separated (segregated)during gamete production
-Alleles reunited by fertilization.Segregation occurs during meiosis (anaphase of meiosis 1 |
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Mendel's Data |
>when crossing one true-breeding homozygous dom. with one true-breeding homozygous recessive, mendel got : 3:1 phenotypic ratio, 3 dominant : 1 recessive >In 2nd generation, got 1:2:1 genotypic ratio: 1 homozygous dominant, 2 heterozygous, 1 homozygous recessive |
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Test Cross |
Performed if trying to decide if a person is homozygous dominant or heterozygous: cross the individual with a homo-recessive and see what you get. IF all dominant, then homo-dom. |
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Di-hybrid Cross |
>examines combinations of two traits at the same time; ex: YYrr X yyrr >This creates a dihybrid: someone who is heterozygous for both traits >alleles for one trait are distributed independently from alleles foranother trait in gametes of a dihybrid plant >After crossing YYRR with yyrr, got a 9:3:3:1 ratio |
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Principle of Independent Assortment |
> Founded from data from dihybrid cross >The segregation of alleles into gametes for one trait isindependent of the segregation of alleles for a second trait. > Due to random alignment of tetrads on the metaphase Iplate. > True only for genes on different chromosomes! > In otherwords, the y's and r's of one plant are unlinked, so the single r or y by itself can be transfered to offspring without other counterpart |
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Mendel's Laws of Genetics |
1. The two alleles for each character separate(segregate) during gamete production: arereunited by fertilization.
2. The segregation of alleles into gametes for onetrait is independent of the segregation of allelesfor a second trait |
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Sutton and Boveri |
recognized striking parallels between the behavior of c’somesduring meiosis and Mendel’s genes.CHROMOSOMAL THEORY OF INHERITANCE:Mendelian genes are carried on chromosomes:chromosomes (and therefore genes) undergo segregationand independent assortment during meiosis.Proof of this theory was provided by THOMAS HUNT MORGANand his colleagues during the early 1900’s.
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Principle of Segregation |
Meiosis I segregates alleles into different cells.Segregation occurs during anaphase I of meiosis I.Meiosis II separates sister chromatids into gametes.Two classes of gametes produced by monohybrid organism (R and r)
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Principle of Independent Assortment |
Gamete production by RrYy dihybridIndependent assortmentduring metaphase I ofmeiosis I.Due to random alignment ofhomologous c’somes atmetaphase I plate.Four classes of gametesproduced (RY, Ry, rY, ry)
REMEMBER: for genes carried on differentchromosomes (unlinked genes), all possible gameteswill be produced in equal numbers via meiosis. AaBbCc individual produces ABC, ABc, aBC, AbC, abC,Abc, aBc, and abc gametes in equal numbers. |
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Alternative Patterns of Inheritance |
Situations leading to deviation from standard >“Mendelian” patterns ofinheritance:
linkage: different genes carried on same c’some >sex-linkage: unusual patterns of inheritance of genes on X c’some >incomplete dominancemultiple alleles >environmental effects |
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How Linkage works |
See slide 13 |
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Frequency of Recombination |
Frequency of recombination is proportional to thedistance between two genes.1% frequency of recombination = 1 map unit.Recombination frequencies can be used to map therelative positions of genes on a chromosome
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Sex-Linkage |
>Consider humans: 23 pairs of homologous chromosomes
>1-22 = autosomes >23rd pair = sex chromosomes (X and Y)human >females = XX, human males = XY. >X and Y c’somes do not have homologous sets of genes! >the Y c’some has few genes: none are essential for survival. >Females produce only gametes with X chromosome. >Males produce gametes with X or Y chromosome in equal numbers. >man determines sex of child |
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Turner's Syndrome |
XO; its a girl |
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Klinefelters’s syndrome (male)
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XXY
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Sex-Linked genes |
Females have 2 X’s; can be homozygous or heterozygousMales have 1 X; can’t be heterozygous for X-linked alleles
>Differences between the phenotypic ratios of male and female progenysuggests that a trait is sex-linked |
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Incomplete dominance |
>heterozygote hasintermediatephenotype
>Phenotypic ratios in F2do not fit expected 3:1ratio! >One good copy of a gene is usually enough >Some gene products present in limiting quantities >Single functional gene does not allow production of sufficient protein. >R allele encodes an enzyme that makes red flower pigment >r allele is a mutant form of the gene that does not produce enzyme >RR Rr rrlots of enzyme ,intermediate level of enzyme, no enzyme :red flowers pink flowers white flowers |
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Polygenic Inheritance |
>Many traits are determined by the combined action of multiplegenes = polygenic inheritance. >Example: human skin color: extremely dark to extremely light.Many genes involved..
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