Equations

Question 1

Coefficient of coincidence

Answer 1

CoC = # double crosses / # expected double crosses

Question 2

Recombination frequency (st - ss - e)
Rf (st - ss) =
Rf (ss - e) =
This is the distance between genes

Answer 2

Rf (st - ss) = [ (Sum double cross) + (Sum single st-ss) / (total progeny) ] *100

Rf (ss - e) = [ (Sum double cross) + (Sum single ss-e) / (total progeny) ] *100

Question 3

Recombination frequency (st - ss - e) meaning

Answer 3

This is the distance between genes

Question 4

Recombination frequency (st - ss - e) 
Rf (st - e) =

Answer 4

Rf (st - e) = Rf (st - ss) + Rf (ss - e)

Question 5

What is the probability that 2 girls and 2 boys will be born?

Answer 5

P = { n! / (s! t!) } x (p^s) (q^t)

Now using this equation, calculate the probability (P) that in 4 delivery rooms (n=4), two boys and two girls will be born (s=2 and t=2). Remember, p= 1⁄2 boys and q= 1⁄2 girls .

P = (24/4) x (1/4) (1/4) = 24/64 = 0.375

Question 6

Two carriers of the recessive allele for cystic fibrosis have six children. What is the probability that:
Two will be normal and four will have the disease?_

Answer 6

P = { n! / (s! t!) } x (p^s) (q^t)

n = 6, s = 2, t = 4
p(normal) = 3/4
q (CF) = 1/4

P = 0.03

Question 7

Interference equation

Answer 7

I = 1 - CoC (CoC coefficient of coincidence)

Question 8

Coefficient of coincidence CoC =

Answer 8

CoC = Observed DCO / Expected DCO

Question 9

Expected DCO =

Answer 9

Expected DCO = RF seg1 x RF seg2 x Total # progeny

Expected DCO = distance seg1 x distance seg2 x Total # progeny

Question 10

Ex. Expected DCO = ?
CoC = ?
Interference = ?
distance seg1 = 21.3 cM
distance seg2 = 17.5 cM
Total # progeny = 1000
Observed DCO = 28

Answer 10

Expected DCO = 0.213 x 0.175 x 1000 = 37.3

CoC = Observed DCO / Expected DCO = 28 / 37.3 = 0.75

I = 1 - CoC = 1 - 0.75 = 0.25