Table of Contents

• Prequiz...
• When linked genes stay linked...
• 1: Punnett Square Redux
• 2: Here's Smiley
• 3: Smiley's First Punnett Square
• 4: But what if the genes are linked?
• 5: Some notation
• 6: Since the linked genes don't separate...
• 7: Here's another one to try
• 7a: Here's another one to try
• ...And when they don't
• 8: But life is not so easy
• 9: Here's how the Punnett Square gets more complicated...
• 10: An easy Question
• 11: How about a general rule?
• The math of crossing over
• 12: But how often does cross-over occur?
• 13: Fun with map units...
• 14: The farther apart the genes are, the more they act like they're unlinked
• Getting an earful
• 15: Putting it all together
• 16: Spock's Ears
• 17: Yoda's Ears
• 18: Recomb - Review

An easy Question

 

Assume both parents are ET/et, and the recombination frequency is 10%, so the chance of a gamete having the eT genotype is 5%.

What is the chance of a child having the eT/eT genotype? (You may or may not want to use the Punnett square below).

ET 45% et 45% Et 5% eT 5% ET 45% ET/ET et/ET Et/ET eT/ET et 45% ET/et et/et Et/et eT/et Et 5% ET/Et et/Et Et/Et eT/Et eT 5% ET/eT et/eT ET/eT eT/eT   There is only one cell in this table with the genotype eT/eT, and you just calculated this occurs with a probability of 0.0025, or 0.25% of the time. However, there are other ways for a child to get wild-type teeth and bug eyes: eT/et or et/eT. Are either of these represented in the Punnett square?

So now for a harder question:

What is the total probability that a child will have wild-type teeth (TT or Tt) but bug eyes (ee)?