What determines who we are?

Genesand

Chromosomes

Evolution

• Evolution is the process by which species change over time.

• This is done by natural selection: random changes to an animal are passed on if those changes help the animal survive and reproduce.

• These random changes are called mutations. How do they happen?

Mutations

• Mutations are random changes to the genetic information of a plant or an animal and can cause the animal to grow in a new and different way.

• Most mutations are neutral – they do not affect an animal’s fitness positively or negatively.

• Some mutations are negative – such as deformed limbs or malfunctioning organs.

• Some mutations are positive – such as larger brains, webbed feet, or better camouflage.

Genes

• Genes hold yourpersonal information

• They control hereditarytraits like eye colourand body function

• Genes are segmentsof DNA

• DNA makes up yourchromosomes

• Each human cell has23 pairs of chromosomes

Chromosomes

• There are 22autosome pairsand one pair ofsex chromosomes

• Sex chromosomescontrol gender

• Females have 2 X chromosomes and males have an X and a Y chromosome

• Autosomes determine other traits

So what does this have to do with mutation?

• Mutation happens at the genetic level

• This happens when the information in the genes gets mixed up

• We know certain syndromes come from mutations in specific chromosomes:-for example Down’s Syndrome comes from having an extra chromosome 21

• One possible mutation:

Recap (1)

• Cells contain chromosomes

• Each chromosome is made up of DNA

• A segment of DNA which controls a trait or body function is called a gene

• When the information in genes is mixed up it is called mutation

• Mutations may or may not change an individual for better or for worse

Recap (2)

• When the mutation helps, the individual is more likely to reproduce and pass on the mutation to future generations.

• When the mutation is harmful, the individual is less likely to reproduce.

• This process is called evolution by natural selection and allows species to change over long periods of time.

Dominant vs. Recessive Genes

• We get one set of 23 chromosomes from each parent

• When the genefrom one set overrules the gene from the other set, that gene is called “dominant”.

• The other gene is called “recessive”.

• The gene for brown eyes is dominant.

Bibliography of images

• http://www.oncolink.org/library/images/id818-1.gif

• http://ghr.nlm.nih.gov/handbook/illustrations/chromosomes.jpg

• http://www.biology-online.org/images/gene_inversion.gif

• http://www.ashg.org/images/dominant.jpg• http://www.detectingdesign.com/images/

DefiningEvolution/defini8.jpg• http://evolution.berkeley.edu/evosite/evo101/

images/drosophila_experiment.gif