The White Tiger

The Story:

People love white tigers. They have long been rumored to exist in the jungles of the Rewa in central India for a very long time, but has never been confirmed. If captured alive, people could prove they existed. In 1959 someone finally caught a live white tiger cub.

The first thing that they had to do was determine if it was a new species of tiger, or if it was an white Bengal Tiger (Panthera tigris tigris) which is also common in the area.

Today, we are going to take the position of the two individuals that found and captured the first white tiger. Our goal is to determine if the white tiger is a new species or if they are just albino Bengal Tigers?

DNA Gel Electrophoresis We got a blood sample from the captured

white tiger cub (named Mohan) and a sample from a Bengal Tiger. We are now ready to run a DNA gel.1. If we are going to run a DNA gel, what 3

things must we do before we can put the DNA in the gel?

2. You try using paper gels!

–Extract the DNA–Cut the DNA with an Enzyme–Add a dye to the DNA sample

Results of the DNA electrophoresis:

Known DNA sizes

Bengal Tiger

White Tiger Cub

So we don’t have a new species…

Bummer, right?

What would have to happen for Mohan, the first white Bengal tiger, to be born like this?

DNA analysis results

We sent in a DNA sample to the West Bengal University of Animal and Fisheries Sciences in Calcutta, West Bengal and had them analyze it.

They found that a different amino acid sequence caused a different protein to be made, which added a new allele to the population.– Normal Bengal tigers are TT for color– Mohan is tt for color

Thought Question

How would we make another white Bengal Tiger?

(Remember, we know that it is tt for the pigment gene.)

Mate Mohan with his offspring

Mohan (tt) vs Offspring (Tt)

½ of the offspring will be heterozygous– Carriers

½ will be homozygous recessive– White tigers

T t

t Tt tt

t Tt tt

And so they did…

What if we wanted to create a tame, white Bengal Tiger?

Wild Bengal Tigers are BB and tame Bengal Tigers are bb.

What would you have to do in order to get a tame, white Bengal Tiger?

Assume we cross bbtt with BbTt

bt bt bt bt

BT BbTt BbTt BbTt BbTt

Bt Bbtt Bbtt Bbtt Bbtt

bT bbTt bbTt bbTt bbTt

bt bbtt bbtt bbtt bbtt

•So what are the odds of getting a well behaved (bb) white (tt) tiger?