PEDIGREES aa aa aa aa aa aa Aa Aa Aa Aa AA or Aa
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