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PEDIGREES
aa
aa aa aa
aa
aaAa Aa
Aa
Aa
AA or Aa
RECESSIVE PEDIGREE
MULTIPLE GENE INHERITANCE
With a fancy background
WARMUPW
hat are the odds of rolling a 6 on a die and pulling an Ace out of a standard deck of 52 cards?
W
hat are the odds of rolling a 6 on a die OR pulling an Ace out of a standard deck of 52 cards?
W
hat are the odds of rolling two die and having a total of 12?
W
hat are the odds of rolling two die and having a total of 11?
WHEN MULTIPLE GENES ARE INHERITED
T
hey are inherited independently of each other*• *with one major exception
S
o we can muse multiplication and addition rules
the same way you did on the warmups
PRACTICE
W
hat are the odds that two parents with the genotype
AaBb mate and have children that express the
dominant phenotype in both traits?
MORE PRACTICE
I
f an AaBbDd parent mates with an AAbbDd parent,
what are the odds the offspring will have the
genotype AABbdd?
SLIGHTLY HARDER PRACTICE
A
n AabbDd man and a aaBbDd woman mate. What are
the odds they have a child with the same genotype
as either one of them?
OTHER WAY TO SOLVE
D
raw a cross of all the possible sperm x all the
possible eggs
D
raw a cross for AaBb x AaBb
EXAMPLE – BLOOD TYPES
I
A, IB dominant to I
+
dominant to – (++ or +- will exhibit + blood)
I
f an individual with AB- blood mates with someone with
BO+- blood, what are the odds they have a child with A+
blood
WHAT 2 PARENTS COULD PRODUCE A CHILD WITH EVERY POSSIBLE BLOOD TYPE? SHOW THE
CROSS
EXAMPLE – EYE COLORF
or the most part, eye color is controlled
by 2 genes on separate chromosomes
I
n gene 1 brown is dominant to not brown.
If the offspring has the brown allele the
second gene is irrelevant
I
n gene 2 green is dominant to blue. This
only matters if the individual is bb in the
first gene
EYE COLOR PRACTICE
T
wo BbGg parents mate. What are the odds their
offspring have each of the possible eye colors?
*NOTE ON EYE COLOR
T
his explains the majority of eye inheritance but it is an incomplete
explanation
F
or some reason that geneticists haven’t figured out sometimes two blue
eyed parents have offspring with other color in the eyes – IT DOESN’T
MEAN YOU WERE ADOPTED OR YOUR MOM CHEATED ON YOUR
DAD
P
robably another gene affects eye color a bit – (e.g. hazel eyes, blueish
greenish eyes, how dark/light the color is etc.)
EPISTASIS
O
ften times one gene acts as a switch for whether or not another gene
can get expressed or not
S
implest example:
I
n mice, black fur color is dominant to agouti (brown)
B
UT this color gene only gets expressed if another gene (the color gene)
is active. Color (C) is dominant to no color (c)
EPISTASIS PRACTICE
I
f two BbCc mice mate, what are the odds of having a
child that is agouti?
SO WHY IS IT HARD TO TRACK MANY TRAITS LIKE HEART DISEASE OR CANCER?
M
any genes are involved, some directly, some via epistasis
S
o it’s trying to figure out a gene that affects a gene that
affects another gene that affects another gene
T
he environment has a huge effect on activating or
deactivating expression of some genes