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Chapter 10.1
Mendelian Genetics
Gregor Mendel
 Austrian Monk
 Studied patterns of _____________ (passing on of
characteristics from parent to offspring)
 Used the common garden pea in experiments.
Why Mendel used peas
 Sexually reproducing: able to isolate both male and
female ___________.
 Easy to identify ____________ (characteristics that
are inherited).
 Short life cycle: grow quickly.
Hybrid
 Any offspring of parents with different traits (ex: tall
plant x short plant).
 ___________________ cross: cross-pollination
(breeding) between two parents with only one variation
difference (ex: tall plant x short plant).
 ___________________ cross: cross-pollination
(breeding) between two parents with two variation
differences (ex: tall, green plant x short, yellow plant).
Pea Cross-Pollination Experiment
Parent Generation (P1)
Tall true breed x short true breed
Filial Generation (F1)
All tall hybrids
Filial Generation (F2)
75 % tall hybrids, 25 % short hybrids
What did Mendel Observe?
When a true-breeding tall
plant is crossed with a
true-breeding short plant
in the P generation, the F1
height trait is always
predictable. _____ are
tall plants.
What happens when the F1
generation are crossed
together?
Mendel observed that in
the F2 generation, the
offspring of F1 plants, are
always in a fixed ratio of
_____; tall:short
Pea Traits that Mendel Identified
Through multiple crosses, Mendel determined that all these
traits displayed a mathematical predictability for ___________.
Seed
Shape
Seed
Color
Seed Coat
Color
Pod
Shape
Pod
Color
Flower
Position
round
round
grey
smooth
green
axial
wrinkled smooth
round
yellow
white
constricted
grey
smooth
yellow
green
terminal
axial
Plant
Height
tall
short
tall
Mendel’s Conclusions
 There must be two variations for every trait, where each
variation is called an ___________.
 Each offspring inherits only _______ allele from each
parent.
 The alleles are either ________________ or
_________________
 To show the recessive trait, ______ recessive alleles
must be inherited.
Dominant and Recessive Traits
 The traits that seem to mask other traits when present
are called _______________ traits.
 The traits that seem to be hidden in the presence of
dominant traits are called _________________ traits.
BB – Homozygous Dominant purple
Bb – Heterozygous purple
Bb – Homozygous Recessive white
Homozygous vs. Heterozygous
 ___________: inherits two
similar alleles from the
parents for a particular gene.
Ex. tall allele and tall allele,
written as _____.
Ex. short allele and short allele, written as _____.
 ________________: inherits two different alleles
from the parents for a particular gene.
Ex. tall allele and short allele, written as _____.
Law of Segregation
 Mendel concluded only ______ allele is passes from
parent to offspring for each trait.
 F1 plants must be __________________ because the P
generation only passed on one tall allele and one short
allele.
 The F1 plant will then pass on to its offspring either a tall
or a short allele, never both.
Using a Punnett Square
 AA x aa = 100% Aa
 Each of the four squares
represents 25% chance of
inheritance for one offspring.
A
A
a
a
Phenotype vs. Genotype
 ______________: physical appearance of the trait.
Ex.: purple flowers.
 ______________: homozygous or heterozygous
inheritance.
Ex. PP, Pp, pp
Law of Independent Assortment
 Because organisms are made up of more than one trait,
Mendel concluded that the inheritance of one trait does
not influence the inheritance of a second trait.
 Example: ____________ of the pea plant doesn’t
influence the __________ of the peas.
* Height is independently assorted from color.
Dihybrid cross to show independent assortment.
 A smooth, yellow pea (______) can pass
on these combinations of genes to its
offspring: ___, ___, ___, or ___.
Modernizing Mendelian Genetics
Gene for hairline Allele: A
 DNA is the basis for inheritance.
Genotype: Aa
 DNA are coiled into ___________________.
 Parts of the DNA that code for a trait are called Gene for hairline Allele: a
_________.
 Some genes have only two alleles and others have more.
Variations on Mendel
 _________________ dominance: the heterozygous
genotype shows a blend of the two parents and not the
dominant allele.
 _________________: the heterozygous genotype
shows both inherited alleles.
Ex. a roan horse coat: AA (dark red) x aa (white) = Aa
(dark red and white)
 Multiple ____________: when there are more than two
alleles that code for a trait.
Ex. ABO blood type
A type = AA or Ao
B type = BB or Bo
O type = oo
AB type = AB
 _______________ trait: when more than one gene
codes for a particular trait.
Ex. fur color, human height, human skin color, eye color.
 Linked genes: Mendel concluded that traits are assorted
independently, but some traits are ____________.
o This means that two genes are almost always
inherited together (red hair, green eyes)
Now let’s practice!!