Mendelian Genetics

• Gregor Mendel


  Monk who joined a monastery to pursue his scientific interests, ended up becoming the father of genetics, experimented using peas
• Model system


  Organism that makes it easy for researchers to answer a specific scientific question, so they can then apply the answer to other, harder to study organisms like humans
• Dominant trait


  When one feature conceals others in offspring, so it's the visible one
• Recessive trait


  When a feature is not visible when mixed with another trait in offspring
• Blending inheritance


  Pre-mendelian way of seeing genetics, assumed that parents genetics are permanently mixed and given to their children, because that's what it looked like
• Pea


  Plant Mendel used to conduct his experiments
• True breeding


  Breeding a plant with itself and selecting offspring to continue with until all offspring are identical to the parent
• P generation


  Crossing one true breeding plant with another, creating the first crossover in Mendel's experiment
• F1 generation


  Plants made directly from the seeds of the P generation, filial generation
• F2 generation


  2 generations down from the P generation, product of filial generation
• Allele


  Version of a gene that codes for a trait
• Law of segregation


  A gamete will only receive one copy of of a gene, which is selected randomly
• Genotype


  Set of alleles carried by an organism
• Phenotype


  Set of an organism's observable features
• Homozygous


  When an organism has two copies of the same allele
• Heterozygous


  When an organism has two different copies of a gene, or two different alleles
• Test cross


  When Mendel would mix a plant with a dominant characteristic and a recessive one to see if it had one or two dominant genes. If it had two, all offspring would have the dominant trait. It it had one, half would have the recessive trait because 50% of its offspring would have 2 recessive genes and the other 50% would have one of each
• Law of independent assortment


  That the alleles for two or more different genes that a gamete receives are sorted independently of each other (so the allele for one gene doesn't influence the allele for another gene)
• Dihybrids


  When a genotype is heterzygous for two genes being looked at
• Phenotypic categories for dihybrids are in ratios of approximately 9 : 3 : 3: 1
• Phenotypic categories for heterozygous genes fall in the approximate ratio of 3 : 1
• Linked


  When genes are close together on the same chromosome, the alleles on the chromosome tend to be inherited as a unit more frequently than not
• Punnett square


  Tabular grid summary of possible maternal alleles with paternal alleles, to determine how many of each genotype would occur
• Probability


  Mathematical way of measuring likelihood
• Empirical probability


  Probability determined by dividing the number of times something happened by how many times it could've happened (20 plants out of 50 had blue flowers, so 2/5 is the probability)
• Theoretical probability


  Probability determined by the information about the rules and circumstances that produce an event. Reflect how many times something is expected to happen relative to the number of times it could possibly occur (you have 1 blue marble and 5 marbles overall, so 1/5)
• Product rule 


  Helps you calculate the theoretical probability of two independent events occurring by multiplying out their probabilities (and rule)
• Sum rule 


  Helps you calculate the theoretical probability of two mutually exclusive events happening by adding their probabilities together (or rule)