Funky PigeonsRevealing the biology of inheritance and selection

Lesson 1

Artificial Selection and Genetics

Picture courtesy John Ross: darwinspigeons.com

Charles Darwin (1809-1882)

“Although man does not cause variability and cannot even prevent it, he can select, preserve, and accumulate the variations given to him by the hand of nature in any way which he chooses; and thus he can certainly produce a great result.”

Charles DarwinThe variation of animals and plants

under domestication, 1868

Amassing evidence of variation from a common ancestor

The Rock Dove

English Fantail

African Owl

English Barb

English Pouter

English Carrier

The power of selection: change is possible

5000 yrs

Picture courtesy John Ross: darwinspigeons.com© Mair Shepherd

Amassing evidence of variation from a common ancestor

Natural versus Artificial Selection

Natural Selection Artificial Selection

CauseEnvironment Humans

Speed of changeSlow Fast

Reason for selection occurring

The selected trait improvesthe organism’s chances of surviving and reproducing

The trait is desirable to human breeders

Effect on fitness

Improves fitness (although only for the circumstances in which it is selected. If conditions change, the selected trait may no longer be advantageous)

Often causes decrease in fitness

The wild pigeon

Picture by Christine Matthews (commons.wikimedia.org)

Blue is recessive

s+s+

Allele for pigeon colour

The allele - Black S, Blue s+

Black is dominant

SS or S s+

Darwin on genetics

“...but it will now be seen that when two birds belonging to distinct races are crossed, neither of which have, nor probably have had during many generations, a trace of blue in their plumage...they very frequently produce mongrel offspring of a blue colour...”

Charles Darwin The variation of animals and plants under domestication, 1868

Pigeon feather colour

Pigeon colour/pattern phenotypes

Solid black

Chequered

Barred

Barless

© Genetics Society of America. From Genetics September 1, 1922 vol. 7 no. 5 466-507 STUDIES ON INHERITANCE IN PIGEONS. IV. CHECKS AND BARS AND OTHER MODIFICATIONS OF BLACK by Sarah Van Hoosen Jones.

Epistasis

• Dominant alleles mask the action of recessive alleles

• Epistasis is an interaction between genes: the action of one gene masks the action of another

• The epistatic gene masks the action of thehypostatic gene