BIOL SCI 215 Lecture Notes - Lecture 2: Quantitative Trait Locus, Chromosome, Haploinsufficiency
28 Jun 2018
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Blended inheritance idea
Traits could blend together in a fluid fashion
Idea pre-dated Mendel, traits blend in each generation
Why was Mendel successful?
1. Used a good model organism
1. Pea plants grown and analyzed in large numbers and several varieties had
been found
2. Have good offsprings
3. Easy to grow
4. Plants can cross-fertilize or self-fertilize
1.1. Plant gametes: Pollen (Male) + ovule (female)
1.2. Self: Can occur with a brush or a bag - transfer pollen to
stigma which leads to progeny and plant grows into an adult
1.3. Cross: Transfer pollen from one plant to another by removing
anthers of the other plant → progeny → adults
2. Examined “discontinuous character traits”
1. Two distinct phenotypes: appearance/characteristic or trait that can be
measured
2. True-breeding strains / Pure-breeding strains/lines
1. Cross it with itself and same population and the generations would be the
same
2. Wrinkliness or roundness of a pea
2. Quantified the data
1. First breeding: F0/P(parental generation) - Pure breeding of round and pure
breeding of wrinkly leading to the first generation (F1) being round peas
2. These round peas self fertilize and this leads to F2 being round:wrinkly (3:1)
Mendel builds a model by:
1. Defining players: Round pea gene having 2 alleles: R and r - round = R and wrinkly =
r
1. Homozygous - same allele such as rr and RR
2. Heterozygous - different allele = Rr
1.1. Only one of the alleles is typically “expressed” ==
shown/displayed
1.2. This is denoted by dominant and recessive
1.3. [taken as an assumption till later chapters]
2. Need an experiment to determine whether alleles are dominant or recessive
3. You can only know by looking at the phenotype of heterozygotes
F0 or P: RR x rr
P gametes: 100% R, 100% r
F1: Rr x Rr
Mendel’s first law
Adults have two versions of each gene (allele)
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Traits could blend together in a fluid fashion. Idea pre-dated mendel, traits blend in each generation. Why was mendel successful: used a good model organism, pea plants grown and analyzed in large numbers and several varieties had been found, have good offsprings, easy to grow, plants can cross-fertilize or self-fertilize. Self: can occur with a brush or a bag - transfer pollen to stigma which leads to progeny and plant grows into an adult. Only one of the alleles is typically expressed == shown/displayed. [taken as an assumption till later chapters: need an experiment to determine whether alleles are dominant or recessive, you can only know by looking at the phenotype of heterozygotes. Adults have two versions of each gene (allele) Gametes receive one allele for each gene and process of choosing which allele transmits is governed by the laws of chance.
