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What determines who we are?. Genes and 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. - PowerPoint PPT Presentation
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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