chromosome mapping

Question 1

map units

Answer 1

• the distance between genes on the same chromosome
• (number of recombinants/number of total offspring) x 100
• can be translated to a % recombination
• the larger the map units, the more likely recombination of the genes will take place

Question 2

Possible crossover scenarios for a dihybrid cross

Answer 2

1) genes A and B are independently assorting - 4 classes of offspring with a 9:3:3:1 ratio
2) genes A and B are tightly linked so that crossing over does not happen - 2 classes of offspring with a 3:1 ratio
3) genes A and B are linked and crossing-over occurs with variation in 3:1 ratio (ex 24:1:1:7)

Question 3

what is the cap % of recombination and why

Answer 3

50% (50 map units)
- if more than 50 % then you are independently assorted

Question 4

cis and trans alleles in a dihybrid cross

Answer 4

cis = AB || ab
trans = Ab || aB

Question 5

tracking linked genes ex: ABO blood type and nail-patella syndrome

Answer 5

often nail patella syndrome is inherited with BO blood, however due to recombination some individuals who have OO blood might appear affected and some with BO may not appear affected