4: Chromosomes & linkage

Question 1

Why are drosophila an ideal model organism for genetics experiments ?

Answer 1

Easy to rear
Rapid gen time
Smaller genome (sequenced before humans)

Question 2

Describe the fly room experiments

Answer 2

T.H. Morgan (early 1900s)
Crossing red-eyed and white-eyed flies
Red = W+ (dominant)
White = w (recessive)

Eye colour gene must lie on the x chromosome

= first demonstration that genes are on chromosomes

Question 3

What does recombination mean for the distance between genes?

Answer 3

More recombination = further apart the genes are

Question 4

Recombination fractions are ________

Answer 4

additive

Question 5

What is a recombination fraction?

Answer 5

measure of the distance between 2 genes

Question 6

What units does a recombination fraction use?

Answer 6

centiMorgans (cM)

Question 7

What is the evolutionary significance of recombination?

Answer 7

Recombination can produce new, fitter genotypes
Recombinant can also break up co-adaptive gene combinations
Recombination can speed up rate of evolution in sexual organisms
Reminder: asexual organisms do not recombine