Mutations
Mutation Changes in sequences (DNA or RNA) Can be caused by an outside factor ( , , or chemicals) or inside factors (during , replication, or synthesis) Can result in changes in DNA or RNA sequences which may have no effect on the final , the of the , or the from properly or . Beneficial mutations: Genetic (change in populations genetic material due to random mutations) increases diversity In rare cases, mutations can cause disease Harmful mutations: Can cause Can have
Types of mutations – deletion of one or more base(s) – one base is replaced by a different base – duplication of a base or a section of bases on the same chromosome – a sequence of bases has its order reversed (eg. TTC to CTT) on the same chromosome – a sequence of bases is deleted from one chromosome and inserted into a different chromosome
Effects of Mutation in Protein Synthesis Frameshift mutation – caused be or by a number of nucleotides not evenly by three. Due to the nature of codons, this type of mutation can disrupt the during protein (affects the amino acids to be incorporated into the polypeptide chain) Nonsense mutation – point mutation that can cause a stop codon in the mRNA. This will result in the early of the chain. Missense mutation – single mutation causes an amino acid to change in the chain. This change results in the change of the protein function due to the of the mutant amino acid (active site) Silent mutation – mutations that do not result in the of the amino acid of the protein. Example: AAA and AAG both code for lysine
Environmental Mutagens Mutagen: or agent that causes in the DNA or RNA Environmental Mutagen: any agent within an which increase the chances of a in . Example: radiation (from the sun’s rays or x-rays) Organic chemicals (such as those found in ) Although some mutagens are and cannot be prevented or avoided, there are some which has a direct effect on the creation of and handling. Advances in , , and has by-products we have a responsibility to own as well.
Examples of Environmental Mutagens , for example , and alpha particles , electromagnetic radiation with a wavelength shorter than that of visible light but longer than x-rays – pesticide (found in insect repellent) Cigarette smoke – used for electrical insulation (causes lung cancer) Benzene, an industrial and in the production of drugs, plastics, synthetic rubber and dyes
Genetic Disorders Cystic fibrosis Muscular dystrophy Down syndrome Turner syndrome Sickle-cell disease Polycystic kidney disease Color blindness http://en.wikipedia.org/wiki/List_of_genetic_disorders
Down Syndrome Due to (faulty spindle fibres during meiosis) Either mom or dad contribute an chromosome (No. 21) during Occurs in out of every births Chances increase with mothers 1/60 chances that a child of a woman the age of 40 will be affected 1/800 chances that a child of a woman the age of 40 will be affected
PKU – Phenylketonuria Missing an enzyme which converts into Build up of phenylalanine causes severe system damage/mental retardation or brain
Sickle Cell Disease Red blood cells shaped like a rather than normal round-shaped Sickle cells cannot pass through small blood vessels, so tissue can become starved for Due to an error in one acid – instead of a , affected individuals have a Symptoms include episodes of Chest pain Bone pain Rapid heart rate
By the end of this section you should be able to: Give examples of two environmental mutagens that can cause mutations in humans Use examples to explain how mutation in DNA change the sequence of amino acids in a polypeptide chain, and as a result may lead to genetic disorders