2 Genetics- the field of biology devoted to understanding how characteristics are transmitted from parents to offspringGenetics was founded with the work of Gregor Johann Mendel
3 Gregor Johann Mendel Austrian monk who experimented with garden peas 1842- age 21; entered a monastery in Brunn1851- entered the University of ViennaHeredity- the transmission of characteristics from parents to offspring
4 Mendel’s garden peasMendel observed 7 characteristics of pea plants, each occurring in 2 contrasting traits.Traits- plant height (long or short stems), flower position along stem (axial or terminal), pod color (green or yellow) pod appearance (inflated or constricted), seed texture (smooth or wrinkled), & flower color (purple or white)
5 Mendel collected seeds from his pea plants He observed that both purple-flower and white-flower plants grew from the seeds of purple-flower plants
6 He also observed that both tall and short plants grew from seeds obtained from tall plants Mendel wanted to find an explanation for the variations
7 Mendel’s methodsMendel documented the traits of each generation’s parents by controlling how much the plants were pollinatedPollination- occurs when pollen grains produced in the male reproductive parts of the flower (anthers) are transferred to the female reproductive part of the flower (stigma)
8 Self-pollination- occurs when pollen is transferred from the anthers of a flower to either the stigma of the same flower or a flower on the same plantCross-pollination- involves flowers of 2 separate plants
9 Self-pollination can be interrupted (and cross-pollination performed) by removing the anthers from a flower and manually transferring the anther to the stigma of another plantBy doing this, Mendel was able to protect his flowers from receiving pollen that might be transferred by wind or insects, giving him more control over the pollination of his pea plants
10 Mendel’s experimentsPlants that are pure for a trait always produce offspring with that traitstrain- denotes plants that are pure for a traitP1 generation- each parental generation
11 F1 generation- the first filial generation F2 generation- the second filial generation
12 Mendel’s Crosses & Results P cross F1 generation F2 generation Actual ratio Probability ratioAxial X Terminal = Axial axial : :1207 terminalTall X Short = tall tall : :1277 shortInflated X inflated inflated : :1Constricted = cons.Green X yellow = green green : :1(pods) yellowSmooth X smooth ,474 sm : :1Wrinkled = ,850 wrink.Yellow X Green = yellow ,022 yellow : :1(seeds) ,001 greenPurple X White = purple purple : :1224 white
13 Recessive & Dominant traits Dominant factor- dominates the other factor of a specific characteristicRecessive factor- the trait that did not appear in the F1 generation but reappeared in the F2 generation
14 Law of segregationStates that a pair of factors is segregated, or separated, during the formation of gametes.
15 Law of independent assortment States that factors for different characteristics are distributed to gametes independently.
16 Chromosomes & GenesMolecular genetics- the study of the structure and function of chromosomes and genesAllele- each of several alternatives of a gene (Mendel's factors are now called alleles.)