Transcript Gregor Mendel

History of Genetics
 Greeks: Theory of Pangenes (particles are passed to
next generation)
 Before 1860: ‘Blending Inheritance’ Red father, and
white mother will have pink offspring
 1860’s: Mendel
Gregor Johann Mendel
 Austrian Monk
 born in 1822 -1884
 His work became recognised
after 1900
Mendel
 Mendel did the first experiments to find out
how different traits are inherited by new
generations
 He used pea plants
Mendel’s work
 Different features of
pea plants
 Flower colour
 Height
 Shape of pea
Genetic crosses
 To cross 2 varieties of
pea plants, Mendel
used a brush.
Tracking heritable characteristics
 Mendel tracked features
for 3 generations.
 P (parents)
 F1 (first generation)
 F2 (second generation)
 Features found in P would
disappear in F1 and come
back in F2
 Always a ratio of 3:1
Mendel’s law of segregation
 He discovered features
can have different
varieties
Mendel’s Conclusions
 There are 2 copies of each gene
 There can be different varieties of these genes
(alleles).
 The variety that you see is Dominant
 The variety that you don’t see is Recessive.
Mendel’s terminology (cont’d)
 Allele = different variety of a gene
 Dominant = The Allele that will be expressed
 Recessive = The allele that is not expressed
 Homozygote = Both alleles are the same
 Heterozygote = Both alleles are different
Mendel’s impact
 Mendel’s theories are equally valid for figs, flies, fish,
birds and human beings.
 Mendel’s impact endures, not only on genetics, but on
all of science, as a case study of the power of
hypothesis/deductive thinking.
Eye colour
 What if…. You would one day meet
or
 Could your children have Blue eyes?
Eye colour
 Brown colour is dominant over Blue
 So your Brown gene will be dominant over the blue gene
 So all children will have brown eyes
 But maybe your grandchildren will have blue eyes
What do you see here
 Do you see a number?
 How many people see
only dots?
 How is that possible?
Colour Blindness
More Examples
 Earlobe attached or not
 Widows peak
 Curled tongue