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true-breeding
flower produce same color byself-pollination in successive generations
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hybridization
mating, or crossing, of two true-breeding varieties
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P generation (parental generation)
true-breeding parents
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F1 generation (first filial generation)
hybrid offspring
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F2 generation ((second filial generation)
F1hybrids to self-pollinate (or to cross-pollinate with other F1 hybrids)
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Mendel experiment
- F1 all purple but F2 3:1 ration of white -> concludes that purple is not destroyed but its dominant and white is recessive
- Conclusion:
- -alternative versions of genes account for variations in inherited characters
- -for each character, an organism inherits two copies of a gene, one from each parent
- -one is dominant allele, the other, the recessive allele
- -law of segregation - two alleles seperate into different gamate
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Locus & alleles
- locus: a spot on chromosome that hold the characters of the traits
- allele: in locus that hold the trait of that character
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homozygous
- has a pair of identical alleles for a character Ex: PP or pp
- - true breeding
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heterozygous
- different alleles Ex: Pp
- not true breed cuz it produde 3:1 (white and purple)
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phenotype & genotype
- phenotype : traits( colors) 1st allele
- genotype : genetic makeup (PP, Pp), 2nd allele
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testcross
Breeding an organism of unknown genotype so it can revealthe genotype of that organism
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monohybrid cross.
- cross between such heterozygotes
- dihybrids: (YyRr) 2 traits
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law of independent assortment
- Mendel’s dihybrid experiments
- each pair of alleles segregates independently of each other pair of allelesduring gamete formation. Ex: color doesnt affect shape
- -dependent (3:1) , independent (9:3:3:1)
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Punnete sqaure
- Rr&Rr = 1/2 Rr, 1/4 RR, 1/4 rr
- Rr&RR = 1/2 Rr, 1/2 RR
find all possible possibilities then add up the products
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codominance
- two alleleseach affect the phenotype in separate
- dominant has enzyme synthesize adequate amounts of branched starch
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Tay-Sachs disease
- inherit two copies of the Tay-Sachs allele(homozygotes)
- qualifies as recessive
- heterozygote condition does not lead to diseasesymptoms
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pleiotropy
Most genes, however,have multiple phenotypic effects
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epistasis
phenotypic expression of a gene at one locus alters that of a geneat a second locus
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quantitative characters
- characters vary in the population in gradations along a continuum
- indicates polygenic inheritance, an additive effect of two or more genes on a single phenotypic character
- AABccc = AaBbCc
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norm of reaction
- arange of phenotypic possibilities due to environmental influences.
- multifactorial - many factors, both geneticand environmental, collectively influence phenotype
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cystic fibrosis,
- European descent, one out of 25 (4%) carries
- chloride transport channels are defective or absent inthe plasma membranes
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