Week of March 17th and Beyond!

Gregor Mendel - Father of Genetics

Links

Mendel's Experiments Interactive

Punnett Square Interactive

Example of Incomplete Dominance - notice how the white and red/brown parent pig colors blended to make the pink pig

This Apaloosa Horse is an example of Codominance.  Black and white alleles were neither dominant or recessive so both color are seen in the horse

The image above is a visual representation of typical human chromosomes.  Notice the various sizes and shapes!  There is an estimated 25,000 genes on these chromosomes that control all of the various human traits.  

The diagram below illustrates the relationship between genes and DNA.  Genes are segments of DNA found in chromosomes that give the instructions for producing specific traits. 

What about alleles?

Gene vs Allele

A gene is a part of the DNA. Alleles on the other hand refer to different versions of the same gene. 

• Genes are the different parts of the DNA that decide the genetic traits a person is going to have. Alleles are the different sequences on the DNA-they determine a single characteristic in an individual.

Week of March 3rd

Natural Selection At Work

Consider the following:

Tardigrade in moss

Is this an alien lifeform? Probably not, but of all the living things that inhabit Planet Earth, this might be the best candidate!  The Tardigrade is an extremophile.  This means that this organism can survive in very hostile conditions...like

• Can live for decades without food and water
• Survive temperatures from above -273 degrees F to 212 degrees F
• Survive pressures from 0 to the bottom of the ocean
• Survive exposure to extreme radiation
• These waterbears are so versatile because they are able to repair their own DNA 

Talk about some extreme natural selection!

African Elephants

African elephants have been hunted for the ivory tusks for many years.  By 1930, 1% of African elephants began to never develop tusks.  Hunters would not kill these elephants without tusks, so the genetic code for "no tusks" was passed along and populations of these elephants with no tusks has grown to about 40 %!  Elephants use their tusks for digging and defense, so life for these tusk-less elephants is quite challenging.  

How will the process of natural selection continue in this situation?

Links for the week:

Us - in 1 minute

K-T Event (Nye)

Asteroid Impact

100 Greatest Discoveries Natural Selection

Darwin's Finches Matching