1. Two-Trait Punnett Problems
TTPp
Ttpp
Two-Trait Punnett Problems
TtPp
ttPp
TTPP
ttpp
TTpp

2. Two Traits at Once!
Every organism has many traits, and we can solve Punnetts for multiple traits at a time
Every trait must be represented by a DIFFERENT letter (like T for tail shape and P for pupil size)
Every trait can be either dominant or recessive (like T for long tail and t for short tail, along with P for wide pupils and p for narrow pupils)

3. Phenotypes describe both traits
Adults and offspring have both traits described in their phenotypes
Examples:
Long tail with wide pupils
Long tail, narrow pupils
Short tail and wide pupils
Short tail with narrow pupils

4. Genotypes have pairs of letters!!!
Adults and offspring have four letters in their genotypes (2 traits X 2 genes for each trait = 4)
Examples:
TTPP (homozygous dominant for both traits)
TTpp (homo dom for one trait, homo rec for the other)
TtPP (hybrid for one trait, homo dom for the other)
TtPp (hybrid for both traits – called a DIHYBRID, or double hybrid)

5. Gametes only get one letter for each trait!!!!
Since sperm and egg cells only get one copy of each gene from each parent, they only have one of each letter – but they get both letters
Examples:
TP (both dominant)
tP (one dom, one rec)
Tp (one dom, one rec)
tp (both recessive)

6. Let’s give it a try!!!
Leopards can have long tails which are dominant over short tails, and they can have wide pupils which are recessive to narrow pupils.
A short-tailed male that is heterozygous for pupil size mates with a female that is hybrid for tail shape and has wide pupils.
Find the phenotype percentages of their offspring (you can skip the genotype percents in your final answer).

7. Step One: Define the alleles
Leopards can have long tails which are dominant over short tails, and they can have wide pupils which are recessive to narrow pupils.
T = long tail t = short tail
P = narrow pupils p = wide pupils

8. Step Two: The Chart (Start with what the problem gives you)
A short-tailed male that is heterozygous for pupil size mates with a female that is hybrid for tail shape and has wide pupils.
Male
Female
Phenotype
Genotype
Gametes
Short tail, Narrow pupils
Long tail, Wide pupils
Ttpp
ttPp
tP or tp
Use these in your Punnett!!!
Tp or tp

9. Step Three: The Punnett Square
Use the gametes from the chart to set up you Punnett. This one is a two-by-two Punnett. You could also have a 2X4, a 1X4, or a 4X4!! tP tp Tp
Ttpp
TtPp tp
ttPp
ttpp

10. Step Four: Final Answer
Find the phenotype percentages of the offspring.
T = long tail t = short tail
P = narrow pupils p = wide pupils tP tp Tp
TtPp
Ttpp
ttPp
ttpp
1 Long tail with wide pupils (25%)
1 Long tail, narrow pupils (25%)
1 Short tail and wide pupils (25%)
1 Short tail with narrow pupils (25%)

11. Another one for practice!
(Do this on the back of your paper)
Lynx can have ear tassles that are either brown (which is the recessive trait) or black. They also have short tails that can either be straight, which is dominant, or their tails can be curled. Find the phenotype percents of offspring from a dihybrid male and a female with brown ear tassles and a hybrid tail.

12. Lynx Problem Hint 1 Always start by defining the alleles:
E = black ear tassles
e = brown ear tassles
T = Straight tail
t = Curly tail

13. Lynx Problem Hint 2
You should have made a chart like this, and started by filling in the parts given in the problem.
Male
Female
Phenotype
Brown Ears &…..
Genotype
EeTt
___ ___ Tt
Gametes

14. Lynx Problem Hint 3
Then work forwards and backwards to get the rest of the geno & pheno.
Male
Female
Phenotype
Black Ears & Straight Tail
Brown Ears & Straight Tail
Genotype
EeTt
eeTt
Gametes

15. Lynx Problem Hint 4
Next figure out the gametes. This is the hardest and MOST IMPORTANT part!!!
Male
Female
Phenotype
Black Ears & Straight Tail
Brown Ears & Straight Tail
Genotype
EeTt
eeTt
Gametes
ET, Et, eT, et
eT, et
Notice that every gamete says “ET” – the question is whether they are big or little Es and Ts!
Make sure to include EVERY possible combo of E & T!

16. Lynx Problem Hint 5
Now you can make a 2X4 Punnett: ET Et eT et

17. Lynx Problem Hint 6 Completed Punnett: ET Et eT et EeTT EeTt eeTT eeTt

18. Lynx Problem Hint 7a Figure out the phenotypes: ET Et eT et EeTT EeTt
E = black ear tassles
e = brown ear tassles
T = Straight tail
t = Curly tail
Black Ears & Straight Tail
Black Ears & Curly Tail
Brown Ears & Straight Tail
Brown Ears & Curly Tail
Count how many of each

19. Lynx Problem Hint 7b Another way to figure out the phenotypes: ET Et
EeTT
EeTt
eeTT
eeTt
Eett
eett
E = black ear tassles
e = brown ear tassles
T = Straight tail
t = Curly tail
I like to draw a shape in each box of the Punnett, and then count them up….
Black Ears & Straight Tail
Black Ears & Curly Tail
Brown Ears & Straight Tail
Brown Ears & Curly Tail

20. Lynx Problem Hint 7c Another way to figure out the phenotypes: ET Et
EeTT
EeTt
eeTT
eeTt
Eett
eett
E = black ear tassles
e = brown ear tassles
T = Straight tail
t = Curly tail
3 Black Ears & Straight Tail
1 Black Ears & Curly Tail
3 Brown Ears & Straight Tail
1 Brown Ears & Curly Tail

21. Lynx Problem Hint 8
Convert the numbers to percentages for your FINAL ANSWER:
3 Black Ears & Straight Tail 3/8 = 37.5%
1 Black Ears & Curly Tail 1/8 = 12.5%
3 Brown Ears & Straight Tail 3/8 = 37.5%
1 Brown Ears & Curly Tail 1/8 = 12.5%
8 Total