Mendelian Genetics An Introduction to Mendelian Genetics: Humans are diploid where they have a copy of each allele (23 chromosomes from dad and 23 chromosomes from mom, making a total of 46) Allele: a specific section on a chromosome that codes for a specific gene (usually two copies for every allele) Homozygous: 2 alleles that are the same (AA or aa) Heterozygous: each allele is different (Aa) In blood type, the O allele is the recessive one Genotypes specifically looked at the genome while phenotypes look for physical traits/characteristics Co-Dominance & Incomplete Dominance: Complete Dominance: when the dominant allele completely masks the recessive allele Co-Dominance: when both alleles show individually in the phenotype (red pedals and blue pedals) meaning both alleles are dominant together Incomplete Dominance: when a heterozygous genotypes shows a mixture of the two alleles (red/blue making purple flowers) Worked Example: Punnett Squares: Law of Independent Assortment (Mendel’s 2nd Law): assumes that if traits are located on independent chromosomes, then the alleles will assort into gametes independently of one another (crossing over can occur if they are far apart from one another) If two alleles are on the same chromosome, then they are what we call linked traits (where they assort together into gametes) Type B or Type A blood means that it could either be BB/AA or even BO/AO respectively Autosome: any chromosome that is not sex-linked Hardy-Weinberg Equation: Hardy-Weinberg Principle: allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences (MUST OCCUR DUE TO RANDOM MATING) Makes some assumptions made in order to generate these stable allele frequencies: no natural selection is occurring that would change allele frequencies, no mutations present, and large populations p = frequency of the dominant trait | q = frequency of the recessive trait | (p + q)2 = (1)2 → p2 + 2pq + q2 = 1 p2 is simply the probability of someone being homozygous dominant q2 is simply the probability of someone being homozygous recessive 2pq is simply the probability of someone being heterozygous Applying the Hardy-Weinberg Equation: 9% has the recessive allele → plug in 0.09 for q2 and take the square root in order to find the frequency of that genotype VERY USEFUL VIDEO, A LOT OF INSIGHT <3