Download Chapter 11 introduction to Genetics

Chapter 11
introduction to
Genetics
Essential Question:
How are chemical
elements arranged in
living things to allow
them to carry on life
processes?
Objectives:
 Describe how
Mendel studied
inheritance in peas
 Summarize
Mendel’s conclusion
about inheritance
 Explain the
principle of
dominance
 Describe what
happens during
segregation
 Explain how
geneticists use the
principles of heredity
 Describe how
geneticists use
Punnett squares
Work of Gregor Mendel
– Austrian botanist
1860s
Biological inheritance –
set of characteristics
inherited from parents
Mendel solved the
mystery to inheritance
 Work as a botanist
 Male reproductive
part of
plants(stamen(anther
+ filament)
 Female
reproductive parts of
plants(carpal aka
pistil(stigma, style,
ovary)
 Fertilization –
pollen(male) and
ova(female) join
 New cell = embryo
of seed
 Peas have both
male and female
reproductive organs –
self pollinate
 Offspring of self
pollinating plants
have “one “ parent –
identical offspring
 True –breeding =
self pollinators
 Mendel’s seed
stock
o Tall plants only
o Short plants only
o Green seeds only
o Yellow seeds only
 Mendel – cross
pollinated his
plants(removed the
stamen) from the
plants
GENES AND
DOMINANCE
 Mendel studied 7
different pea plant
traits
 Trait = a specific
characteristic that
varies from one
individual to
another(seed color,
height, etc)
 Cross pollinated
the two contrasting
characteristics(gree
n and yellow seeds)
 P = parental
generation
 F1 = first filial
generation
(offspring)
 Hybrid = offspring
of parents with
different traits
 Results = no
blending
 All offspring had
trait of only ONE
parent
 One trait
“disappeared
 2 conclusions
o #1 biological
inheritance is
determined by
factors that are
passed from one
generation to the
next – chemical
factors that
determine traits
are called GENES
– each trait is
controlled by ONE
gene that occurs
in 2 contrasting
forms – Example:
o Gene for height
– Tall form/short
form
o Different forms
= alleles
PRINCIPLE OF
DOMINANCE
 Principle of
dominance states
that some alleles
are dominant and
others are recessive
 If the dominant
allele is present the
organism will
ALWAYS exhibit
that form of the
trait
 A recessive form
of the trait will only
be exhibited if the
DOMINANT form is
NOT present
 Tall =
dominant/short
recessive
 Yellow seed color
dominant/green
recessive
SEGREGATION
 What happened
to the recessive
trait
 Mendel allowed
the hybrid
offspring(F1) to selfpollinate for F2
generation
 Result of F1 cross
¼ of the F2 showed
the recessive trait!
 Mendel’s
assumptions – the
allele for shortness
“separated” from
the allele for
tallness
 During the F1
formation of sex
cells (gametes) the
alleles segregated
 When each F1
plant produces
gametes, 2 alleles
separate, so each
gamete carries only
ONE copy of the
gene – those will
Tall gene – some
with short
 Tt X Tt  T,t,T,t
(gametes)  TT, Tt,
Tt, tt(F2)
PROBABILITY AND
PUNNETT SQUARES