Dihybrid Problems

1
Dihybrid Problems

• Definition Genetics Problems with two traits
  tracked at the same time
• Try This
• Given B brown hair, b blond hair AND T Tall
  while t short.
•  
• BbTt ______________ phenotype
• Bbtt ______________ phenotype
• bbTT ______________ phenotype
• bbtt ______________ phenotype
•  
•  

Brown, Tall
Brown, Short
Blond, Tall
Blond, Short
2
Arrow Rule

• When drawing your sperm and egg for the 7 steps
  in this type of problem each
• Sperm contains __________ genes?
• Egg contains __________ genes?
• Predict the sperm or eggs possible for a critter
  of BbTt.
• Arrow Rule

2
2
BT, Bt, bT, bt
3
Dihybrid gamete formation

• What sex cells could be obtained from the
  genotypes below?
•  
• Bbtt ___________, ___________, ___________,
  ___________
• bbtt ___________, ___________, ___________,
  ___________
• BBTT ___________, ___________, ___________,
  ___________
• BbTt ___________, ___________, ___________,
  ___________
• Hint repeated sperm or eggs can be crossed out.

Bt Bt bt bt
bt bt bt bt
BT BT BT BT
BT Bt bT bt
4
DihybridCross a totally heterozygous brown eyed
tall girl with a heterozygous brown eyed
homozygous tall guy.
Do together on board