HOW DO CHANGES IN DNA AFFECT PROTEIN SYNTHESIS? W H Y I S I T I M P O R T A N T T H AT GENE EXPRESSION IS R E G U L AT E D ? ALL OUR DNA IS FOUND INSIDE THE NUCLEUS OF EVERY SINGLE CELL IN OUR BODY! (MINUS YOUR REPRODUCTIVE CELLS) The DNA inside these blood cells is exactly the same as the DNA in these nerve cells! SO, IF WE HAVE THE SAME DNA IN ALL OUR CELLS… WHY DON’T WE HAVE ARMS GROWING OUT OF OUR HEAD?! OR EYEBALL PROTEINS BEING MADE IN OUR HEART??!! GENE EXPRESSION: the processes by which the information in a gene is put to work. When a gene is “expressed”, it is being actively coded into mRNA and amino acid sequences (protein synthesis). Not all of an organism’s DNA is expressed all of the time. For example, a heart cell does not and cannot express the DNA that an eyeball expresses. Both of these cells have the same DNA but are expressing different parts of the DNA. Gene expression can be compared to a light switch… Heart proteins will NOT be created if the DNA strand is NOT being transcribed in the heart cells themselves! Eyeball proteins will be created if the DNA strand is being transcribed in the eyeball cells! WHAT VARIES IN OUR DNA? Mutations occur by changing the sequence of the nitrogen bases in DNA, resulting in different proteins. Differences between organisms occur because the sequence of the nitrogen bases is different in each organism (mixture of both parents) DNA MUTATIONS: Mutation - Change in a DNA sequence that affects genetic information; error or mistake in copying DNA. POLYDACTYL BABY WITH MASSIVE AMOUNTS OF MUSCLE ANIMALS WITH PIGMENT (COLOR) MUTATIONS 2 TYPES OF MUTATIONS: 1. Point Mutations - Mutation that only affects a single nucleotide at one point. Substitution – one nucleotide base is changed, or substituted for another. This example of a substitution would Original: AUGUAC → Met – Tyr cause the amino acid Mutated: AUGUAG → Met – Stop chain to stop protein production too early! 2 TYPES OF MUTATIONS: 2. Frameshift Mutations - Mutation that shifts the reading frame of the entire genetic code by inserting or deleting a nucleotide. Insertions – A base is added into the DNA sequence. Deletions - A base is removed from the DNA sequence. Original: The fat cat ate the wee rat. Frame Shift: The fat caa tet hew eer at. deletion Frameshift mutations affect all subsequent amino acids after the mutation takes place! SIGNIFICANCE OF MUTATIONS Many mutations have little or no effect on the expression of genes. Mutations may be harmful and may be the cause of many genetic disorders and cancer. Mutations may be a source of genetic variability in a species (may be highly beneficial for the ecosystem).