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?

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 TYPESI

A, IB 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 COLORF

or 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.)

EPISTASISO

ften 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