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Mendelian Genetics
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Iowa State University
What were two original theories on heredity?
a. Blending - genetic material from parents mix together in offspring. Many
generations of sexual reproduction will result in a uniform population of individuals (white
and red, all pink eventually)
b. Particulate - genetic material from parents are passed to offspring as discrete units.
cna be sorted and passed along in undiluted form generation after generation.
What is a character and a trait? How would this be related to a gene and an allele?
character - heritable feature, trait a specific variant of a character
gene - allele two or more forms of a gene
What is phenotype and genotype?
pheno - physical, geno- DNA ‘phenotype is not genotype!’
Describe Medel’s experiment (what he did)?
True breeding, cross pollinated, self bred F1s and determined and counted traits
What were 3 important choices he made to structure his study?
1. True breeding - self fertilized
2. Work with discrete, categocial characters - either/or
3. Tracked for 3 generations
What results did he find?
Offspring traits were not blended, genes act as particles. one from each parents one trait was
dominate but the recessive would show up again in distinct ratios. particles segragate during
sexual reproduction (gametes) and combine at fertilization
alternative versions of genes account for variation in inherited characters, organisms get two
alleles for each character - alleles are dom or rec relative to other alleles (no one allele to rule
them all) and the two alleles segregate during gamete formation
What is the Law of Segregation? Vs Law of Independent Assortment
alleles are segregated during gamete produciton, each gamete has only 1 allele - 4 equally
likely combo PUNNETT SQUARES
each pair of alleles segregates separately of other alleles paris during gamete formation for
characters on diff chromosomes
What is phenotype and genotype? What is hetero and homozygous genotype? How can you
determine genotype?
pheno - physical, geno- DNA ‘phenotype is not genotype!’ -- Pp and PP -- Test cross Test cross - breed with homo recessive
How was Mendel luck with his experiments?
1. Traits exhibit complete dominance
2. two alleles per characteristic
3. single gene controls character
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