DIHYBRID CROSSES We’re still thinking MENDELIAN genetics (2 possible phenotypes) (Upper case and lower case letters)

How many different genotypes can you get when you cross a wrinkled seed pea plant with a smooth seed pea plant? (W=wrinkled, w=smooth)

How many different genotypes can you get when you cross a green seeded pea plant with a yellow seeded pea plant? Does it matter if they’re wrinkled or smooth?

(W=wrinkled, w=smooth) (G=green seed, g=yellow seed) What if you cross a wrinkled, green seeded plant with a smooth yellow seeded plant?

Mendel’s Law of Independent Assortment says… Two (or more) traits on different chromosomes are inherited independently of each other That means the offspring can be green or yellow, wrinkled or round

What are the possible gamete combinations we could have with 2 heterozygous parents? GgWw GgWw ? ?

Use the FOIL method to find gametes! (write this in your handout) F – First allele of each trait O – Outside of both traits I – Inside of both traits L – Last allele of each trait GgWw GW Gw gW gw

Practice setting up the crosses for number 2 Mendel’s Law of Independent Assortment states that gene pairs separate independently of each other. That means two traits don’t have to be inherited together. Practice setting up the crosses for number 2 R R D D R r d d R r D D r r d d r r D d R r D d

Plugging it into a Punnett Square: RD Rd rD rd

Tips for filling in a dihybrid cross Always keep the traits in the same order Keep letters from the same trait together Write dominant letter first… ONLY IF YOU CAN Try #3

Check your work on #3 P RD Rd rD rd RRDD RRDd RrDD RrDd RRdd Rrdd rrDD rrDd rrdd Red with Diamonds White with Diamonds Red without diamonds White without diamonds

Practice on your puppy sheet: Two parents are heterozygous for floppy ears and long hair: F f H h Find the gametes

Practice on your Puppy Genetics sheet: Show the cross for two parents that are heterozygous for floppy ears and long hair F = floppy ear H = long hair f = pointy ear h = short hair Cross _______ _______ ___ ___ ___ ___ ___ ___ ___ ___ P

___ ___ ___ ___ ___ ___ ___ ___ More practice Cross _______ _______ ___ ___ ___ ___ ___ ___ ___ ___ P

Polygenic Traits – pg 216 Same setup – different phenotypes Cross _______ _______ ___ ___ ___ ___ ___ ___ ___ ___ Really short Short Medium Tall Really Tall