BIO 213-F09 - Lecture 3 & 4 - Mendelian Genetics & Punnett Square

BIO 213-F09 - Lecture 3 & 4 - Mendelian Genetics & Punnett Square

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Genetics
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Genotype & Phenotype
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Mendel’s Pea Plants & Their Traits
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Punnett Square Example:
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Punnett Square Problems In rabbits, black fur is dominant over white fur. A rabbit breeder who wants all black furred rabbits on his farm has a black furred male rabbit of unknown genotype. How could this farmer determine the rabbits genotype by breeding him with his female rabbits of known genotypes?
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OK How About Two Traits??
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Dihybrid Punnett Square Say we took a couple of Mendel pea plant traits. Purple flowers are dominant over white and Tall pea plants are dominant over short. What is the phenotypic ratios when two heterozygous pea plants for both traits are crossed? Hint: this requires 16 total squares!!
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Dihybred Cross Chin fissure (butt chin) is dominant over smooth chin Let the letter C represent this trait Dimples are dominant over no dimples The letter D represents this trait A man and woman, both heterozygous for both traits, marry and have a child What is the probability this child will have no dimples or a butt chin?
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NonMendelian Genetics
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Codominance Heterozygous displays both phenotypes both alleles are expressed Example Human Blood Types
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Antigens and RBC Homozygous for I A have blood type A & antigen A on surface of rbc Homozygous for I B have blood Heterozygous, I A I B , have both Homozygous ii, blood type O doesn’t produce any antigens
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Multiple Alleles More than 2 forms at a given locus = multiple alleles In diploid organisms only 2 alleles can be present at one time Human blood type is determined by I A , I B and the allele i Heterozygous I A i - do not exhibit codominance like I A I B individuals, but the I A is completely dominant over the i
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Population A B AB O US Whites 39.7 10.7 3.4 46.3 African-American 26.5 20.1 4.3 49.1 Africans 25.0 19.7 3.7 51.7 US Amerindian (Naaho) 30.6 0.2 0.0 69.1 Japanese 38.4 21.9 9.7 30.1 Russians 34.6 24.2 7.2 34.0
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Ok, so back to mistakes… What about when the DNA is copied incorrectly or chromosomes get messed up in cell division?
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Gene Mutations Base-Pair Substitutions Insertions Deletions
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