PEDIGREES aa Aa AA or Aa

RECESSIVE PEDIGREE

MULTIPLE GENE INHERITANCE With a fancy background

WARMUP  What are the odds of rolling a 6 on a die and pulling an Ace out of a standard deck of 52 cards?  What are the odds of rolling a 6 on a die OR pulling an Ace out of a standard deck of 52 cards?  What are the odds of rolling two die and having a total of 12?  What are the odds of rolling two die and having a total of 11?

WHEN MULTIPLE GENES ARE INHERITED  They are inherited independently of each other* *with one major exception  So we can muse multiplication and addition rules the same way you did on the warmups

PRACTICE  What are the odds that two parents with the genotype AaBb mate and have children that express the dominant phenotype in both traits?

MORE PRACTICE  If an AaBbDd parent mates with an AAbbDd parent, what are the odds the offspring will have the genotype AABbdd?

SLIGHTLY HARDER PRACTICE  An 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  Draw a cross of all the possible sperm x all the possible eggs  Draw a cross for AaBb x AaBb

EXAMPLE – BLOOD TYPES  I A, I B dominant to I  + dominant to – (++ or +- will exhibit + blood)  If 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 COLOR  For the most part, eye color is controlled by 2 genes on separate chromosomes  In gene 1 brown is dominant to not brown. If the offspring has the brown allele the second gene is irrelevant  In gene 2 green is dominant to blue. This only matters if the individual is bb in the first gene

EYE COLOR PRACTICE  Two BbGg parents mate. What are the odds their offspring have each of the possible eye colors?

*NOTE ON EYE COLOR  This explains the majority of eye inheritance but it is an incomplete explanation  For 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  Probably another gene affects eye color a bit – (e.g. hazel eyes, blueish greenish eyes, how dark/light the color is etc.)

EPISTASIS  Often times one gene acts as a switch for whether or not another gene can get expressed or not  Simplest example:  In mice, black fur color is dominant to agouti (brown)  BUT this color gene only gets expressed if another gene (the color gene) is active. Color (C) is dominant to no color (c)

EPISTASIS PRACTICE  If 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?  Many genes are involved, some directly, some via epistasis  So it’s trying to figure out a gene that affects a gene that affects another gene that affects another gene  The environment has a huge effect on activating or deactivating expression of some genes