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heterozygote
individual organism posessing 2 different alleles at a locus.
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mendel experiment
- parents: PP and pp
- F1, all Pp
- F2: 25% pp, 75% P_ ( 50 % Pp, 25 % PP)
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Probability rules:
- 1. when want TWO events to occur (that are indep.), use MULTIPLICATION
- 2. if cool with either OR, use SUM
- 3. DEPENDENT situations:
- subtract from total, ex/ marbles in bag
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chromosome theory of heredity
chromosomes as carriers of genetic material
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sex X-linked characteristics:
male patterned baldness, eye color of fruit flies, cat coat color
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penetrance
- 1. allele does not always penetrate into phenotype of individual
- 2. polydactyl, high expressivity if lots of digits, only one skin tag = low expressivity
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recessive lethal
- if one allele of lethal one is present, doesnt effect organism. effects organism with both of that allele.
- ex/ if Y lethal, YY , NOT yy or Yy
- ex/ if y lethal, yy, NOT YY or Yy
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How genes can interact
- 1. novel phenotype: 2 genes can combine to affect a single trait
- ex/ fruit color of pepper
- 2. epistasis: effects of 1 gene pair masking another gene pair
- a. "allelic" between 2 different genes
- b. masking gene: epistatic
- c. hidden gene: hypostatic
- ex/ bombay phenotype
- squash coloration
- 3. complemetation: crossing mutant genes to see if you can restore a wild type
- (see if (more than) one recessive allele is on same locus, )
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incomplete dominance vs. co-d
- 1. in: somewhere in middle of rec. and dom.
- 2. co-d : hetero is rec + dom. only!
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cytoplasmic DNA
- 1. extranuclear genes found in organelles in cytoplasm
- 2. Mitochondrial genome:
- a. circular DNA
- b. 37 genes
- c. circular dsDNA
- d. 2-10 copies of mtDNA molecule in each mitochondrian
- e. high mutation rate
- 3. usually inherited maternally
- 4. exhibits extensive phenotypic generation ( no meiosis /mitosis, so like blue eyes in one cell and naturally crabby behavior in another... not really but get the gist of the analogy?
- 5.
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cytoplasmic inheritance
- 1. equal no. of mitochondria w/wild and mutant type genes
- 2. progeny have variety of wild and mutant in each cell
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mechanism in differences in severity
- 1. mother, normal to 20% mutant genes
- 2. bottleneck effect: number of mitochondria increases in a cell, some mutated mitochondria selected and therefore magnified in multiplication
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Genetic Maternal Effect:
- 1. genes are inherited from both parents but... P1: S+
- M1: S
- 2. kid1: S+S, offspring G: Dextral, P:SINISTRAL (mother's phenotype, DOESNT matter what papa is)
- 3. now kids 2: (mom is S+S, so P:S+S), but Genotype: (1/4)S+S+ 1/2 S+S 1/4SS
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genomic imprinting
- silencing of one inherited gene
- b. reversible: male getting silenced gened from mom will pass on (possibly) an unsilenced gene
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pleiotropy
- one gene effects multiple characteristics
- ex/ recessive lethal
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Models of transmission I, II, III
- I. Independent Assortment: 2 genes on 2 different homologous pairs of chromes.
- a. 4 dif. types of gametes
- II. Complete Linkage: 2 genes on a single pair of homologs: no exchange occur
- b. two dif. types of gametes
- III. Recombination: 2 genes on a single pair of homologs: exchange occurs between 2 nonsister chromatids
- a. 4 dif. types of
- a.
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completely linked
(no cross over), so same as parents
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incompletely linked
- assort independently,
- 1/2 of progeny are recombinant and half the progeny are not
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