Genetics - Midterm

• Genetics


  The study of biologically variation and traits
• Gregor Johann Mendel


  Father of Genetics
• Gregor Johann Mendel's lifespan


  July 22, 1822 - January 6, 1884
• Trait


  Depends on the passing-on of units/genes
• Dominant trait


  The visible form
• Recessive trait


  The hidden form
• William Harvey's treatise on reproduction and development


  Proposed the theory of epigenesis - structures such as body organs are not initially present in the early embryo but instead are formed de novo (anew)
• Alleles


  The alternate forms of genes
• Cell theory


  All organisms are composed of basic units called cells, which are derived from similar preexisting structures
• Homozygous


  When the two alleles that form the pair for a trait are identical (AA, aa)
• Charles Darwin's Origin of Species

  • Existing species arose by descent with modification from other ancestral species
  • Slight but advantageous variations will accumulate over a long period of time
  • If a population bearing these inherited variations becomes reproductively isolated, a new species may result
• Darwin lacked an understanding of the genetic basis of variation and inheritance
• Heterozygous


  When the two genes are different (Aa, aA)
• Genotype


  The pair of alleles in an individual that are responsible for the expression of a certain trait
• Phenotype


  The observable characteristics of an individual
• Genetic variation


  • Discovery of a white-eyed fruit fly in a bottle containing normal (wild-type) red-eyed flies
  • Mutation in one of the genes controlling eye color
• Probability


  A mathematical measure of likelihood or a likelihood that a particular event will occur
• Monohybrid crosses


  Observes the inheritance pattern of one character
• Empirical probability


  Calculated by dividing the number of times the event occurs by the total number of opportunities for the event
• Mutation


  Any heritable change and are the source of all genetic variation
• Dihybrid crosses


  Mendel crossed varieties of peas that differed in two characteristics
• Genetic event


  • Round seed produced by a pea plant
• Mendel demonstrated that the probability that the event "round seed" was guaranteed to occur in the F1 offspring of true-breeding parents, one of which has round seeds and one of which has wrinkled seeds
• By the 1920s, scientists were aware that proteins and DNA were the major chemical components of chromosomes
• When the F1 plants were subsequently self-crossed, the probability of any given F2 offspring having round seed was now three out of four
• Law of Dominance


  When mating occurs between two organisms of different traits, each offspring exhibits the trait of one parent only. If the dominant allele is present in an individual, the dominant trait will result. The recessive trait will only if both alleles are recessive.
• Avery, MacLeod, and McCarty's experiments

  • Showed that DNA was the carrier of genetic information in bacteria
• In large population of F2 offspring chosen at random, 75% were expected to have round seed, whereas 25% were expected to have wrinkled seeds
• DNA


  Carries genetic information
• Mendel was able to calculate probabilities and use these to predict outcomes of other crosses
• Punnett square


  Developed by Reginald Punnett in 1917, it provides a simple and convenient method for tracking the kinds of gametes produced as well as all possible combinations that might occur at fertilization
• Development of DNA cloning

  1. Restriction enzymes cut any organism's DNA at specific nucleotide sequences, producing a reproducible set of fragments

  2. Allows making large numbers of copies of DNA sequences
• Product rule


  The probability of two independent events occurring together can be calculated by multiplying the individual probabilities of each event occurring alone
• Law of Segregation


  Both alleles of a given gene-- one inherited from the mother, the other from the father-- are expressed equally in each offspring. The two alleles for each trait separate (segregate) during gamete formation, and then unite at random, one from each parent, at fertilization.
• Sum rule


  The probability of the occurrence of one event or the other of two mutually-exclusive events, is the sum of their individual probabilities
• Biotechnology


  The use of modified organisms or their products
• Phenotypic ratios


  • 3:1
  • 1:1
  • Uniform progeny
• Probability of one coin coming up heads and one coming up tails

  • (1/2) x (1/2) + (1/2) x (1/2) = 1/2
• Mendel examined large quantities of pea plants to calculate the probabilities of the traits appearing in his F2 generation
• Chromosome


  Thread-like structures located inside the nucleus of animal and plant cells, made of protein and a single molecule of DNA