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Mendelian Mendelian ExceptionsExceptions
Chapter 12Chapter 12
Section 4Section 4
Mendel’s Principles Revisited
Inheritance of biological _____________ is determined by individual units known as ______.
During sexual reproduction, genes are passed from parents to _________.
Two or more forms of the gene for a single _____ exist, some forms of the gene may be _________ and others may be recessive.
characteristicscharacteristics
offspringoffspring
genesgenes
traittraitdominantdominant
Mendel’s Principles Revisited
Organisms typically have ____copies of each gene, (one from each _______)
An organism’s _____ of genes (2 alleles) are segregated from each other when ________ are formed.
Alleles for different ______ usually segregate _____________ of one another. (through meiosis)
(Law of Independent Assortment)(Law of Independent Assortment)
independentlindependentlyy
parentparenttwotwo
gametesgametesgenesgenes
pairpair
Independent Assortment in Peas
__ Round yellow__ Round green__ Wrinkled yellow__ Wrinkled green
99333311
1.Incomplete Dominance
In incomplete dominance, neither allele is __________ so there is a blending of ______ when two different alleles for the same trait occur together.
Colors blendblend together (______________
individuals = 3rd phenotype)
dominantdominanttraitstraits
heterozygousheterozygous
red whitepink
Incomplete Dominance
In Four O’ Clocks, if you cross a red _____(which is always pure) with a white _____ (that is also always pure) , you get apink _____ (whichis always hybrid /heterozygous
RRRRWWWW
RWRW
RWRW
RW RW
Incomplete Dominance
In another flower, if red ____ and blue ____ flowers are crossed, they produce a 3rd purple ____ flower
What would be the genotype ratio and phenotype ratio if you crossed two purple flowers?
RRRRBBBB
RBRB
2.Codominance Both _______ contribute to the
phenotype of the organism by showing up simultaneously (at the same time) in heterozygous individuals.
In cattle and horses, if you cross a pure ____ (RR) with a pure ______ (WW), you get (RW) which produces the color _____.
allelesalleles
redredwhitewhite
roanroan
Codominance
These cattle or horses actually have both red and white hairs intermixed, or are spotted. Roan is a third ___________.
If you cross a roan with a white…
W
W
R W
WWRW
RW WW
phenotypephenotype
roan
roan
white
white
Codominance Andalusian chickens also show this
pattern of inheritance. If you cross a black (BB) chicken With a white (WW) chicken You get black+white speckled (BW)
chicken
3.Multiple Alleles
In this pattern of inheritance, the genes have more than _____ alleles controlling them and are therefore said to have multiple alleles. No individual has more than _____ alleles, but there are more than _____ possible alleles in a population, so a ______ will be expressed in more than two forms.
twotwo
twotwotwotwo
traittrait
Multiple Alleles
Blood type in humans is an example of this inheritance pattern.
The ______ different blood groups:
A, B, O, and AB Are produced
by ______ different alleles:
A, B, and O
fourfour
threethree
Phenotype Genotype
A AA or AO
B BB or BO
AB AB only
O OO only
Multiple Alleles Examples of Blood type crosses
Phenotype(Blood Type
Multiple Alleles
Genotype
Blood Groups
Antigen on Red Blood Cell
Safe Transfusions
To From
Multiple Alleles
The example of _______ hair color, which has at least four different alleles, is seen in these different Rex rabbits.
rabbitrabbit
4. Polygenic Traits
Traits controlled by two or more genes Show a wide range of phenotypes The phenotype
is produced by the interaction of more than ________ of genes.1 pair1 pair
Polygenic Traits These are called ___________ traits,
which means “having _______ genes”. In humans, _____ color, _____ color,
polygenicpolygenicmanymany
skinskineyeeye
Polygenic Traits These are called ___________ traits,
which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color
polygenicpolygenicmanymany
skinskineyeeye
hairhair
Polygenic Traits These are called ___________ traits,
which means “having _______ genes”. In humans, _____ color, _____ color, and _____ color are just a few of
the many traits __________ by many genes.
polygenicpolygenicmanymany
skinskin
controlledcontrolled
eyeeye
hairhair
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