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Genetics
Inquiry activity: page 262
Gregor Mendel
 Father of modern genetics
 Worked with garden peas
Some basic processes
 Fertilization – during sexual reproduction
the fusion of male and female
reproductive cells (two haploid cells
combine to create a new diploid cell)
 True-breeding – pea plants that when self
pollinated would create offspring identical
to themselves (these where the key
elements in his experiments)
Genes and Dominance
 Mendel studied seven different traits
 He crossed various plants with a variety
of these traits
 Results on page 264
Genes and dominance
 Genes – sections of DNA that determine
certain traits (seed shape)
 Alleles – different forms of a gene
(smooth or constricted)
 Some alleles are dominate (capital letter)
and some are recessive (lower case)
 The dominate alleles mask the recessive
ones
Segregation
 Did the recessive traits dissappear?
 No!
 When Mendel crossed two of the F1
generation (first generation) the
recessive alleles reappeared in the F2
generation (second generation)
Segregation
 Mendel concluded that alleles separate
from each other during the formation of
gametes (sex cells)
 During gamete production the two alleles
segregate from each other so that each
gamete carries only a single copy of each
gene
Probability
 The likelihood that a particular event will
occur
 Coin toss (independent events)
 Probability can be used to predict the
outcome of genetic crosses
Punnett Squares
 Shows gene combinations that might
result from a genetic cross
 Homozygous – organisms that have two
identical alleles for a trait (true breeding)
 Heterozygous – organisms that have two
different alleles for a trait (carriers)
 Phenotype – physical appearance (tall)
 Genotype – genetic make-up