Assessment - The Hairy Tree Rat
You may wish to open the assessment now so you can see the questions you need to answer as you work through the next few pages. The assessment can be found in CMB1005 on Canvas in the Strand D under Genetics Practical 3:
gene
Linkage. If you cannot see your assessment please email
Dr Jeremy Brown.
You decide to set up some crosses.
You cross a Rusty coated with a Tan coated rat = all Rusty coated rats (litter 1)
You cross one of the Rusty coated rats from litter 1 with another Tan coated rat and get litter 2 of 50% Rusty coated and 50% Tan coated rats (litter 2).
Knowledge point: What do these crosses tell you about the relationship between Rusty and Tan coat colours?
You cross a Rusty coated rat with a Brown coated rat and get all Rusty coated rats (litter 3)
You cross one of the Rusty coated rats from litter 3 with another Brown coated rat and get 50% Rusty coated and 50% Brown coated rats (litter 4)
Knowledge point: What do these crosses tell you about the relationship between Rusty and Brown coat colors?
You cross a Brown rat and a Tan rat and get all Rusty coloured rats (litter 5)
Knowledge point: What do these crosses tell you about the relationship between Brown and Tan colour?
Knowledge point: Usually you would assign the letter as the
recessive trait (and designate the
dominant version as uppercase or with a + (e.g white eye fly is w, brown eye is w+)), however as we do not know the
recessive trait then for ease of use the letter of the colour could be used (e.g. B/b for brown and T/t for tan etc.).?
Hint: while the relationships are not the same, you may want to consider the coat colours of Labrador retrievers if you are struggling to figure out the number of
genes and the relationship between them.
You cross two rats from litter 5 and expect to get which result?
Knowledge point: What do you notice about the ratios and the expected results?