Lesson 3 Genes and Mutations.pdf - UNIT 3 Lesson 11 Genes...

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UNIT 3: Lesson 11-- Genes and MutationsOverviewIn this activity you will study the genes and how they can mutate. You will also look at how our understanding of DNAhas improved technology such as gene modification and recombinant DNA.Genes and MutationsLessonTo recap, you have studied DNA structure, replication, transcription, and translation.In this activity you will study the mutations that can arise in the DNA and how genes can be regulated.Types of MutationsApoint mutationis an error at a single point in the DNA. It may be due to a deletion of a base pair or the insertion ofa base pair that can cause a frameshift mutation. That causes a shift so the codons are now read differently. There canalso be a substitute in a base pair - changing the codon so a different amino acid is translated.Some of the mutations that occur aresilent, meaning that the mutation does not affect the function of the protein oraffect the cell’s metabolism. Other mutations may bemissensemutations. This type of mutation can be harmfulbecause the protein can be altered.1. CAU – UUG – ACU – CCC- GUU (normal mRNA)Hisleuthrpro – val2. CAU – UUG – ACU – CCC- GUC (silent)his –leu– thrpro – val3. CAU – UAG – ACU – CCC- GUU (nonsense)his - stopAn example of a missense mutation is Sickle Cell Anaemia. In this disease, an error in the DNA results in all the redblood cells taking on an irregular curved shape (sickle shape) and making them fragile and breaking easily. At the DNAlevel, the codon coding for the amino acid has changed from GAG to GTG therefore glutamic acid becomes valine. As aresult, the tertiary and quaternary structure of the protein is affected and the molecule becomes clumped. Sickle cellanaemia affects millions of people around the world. The disease occurs in about 1 in 500 African Americans, withabout 1 in 10 carrying the disease.Other Mutation Types
Other types of mutations also occur on chromosomes:Deletion– a part of a chromosome is missingDuplication– a part of a chromosome is duplicated morethan one timeInversion– a part of a chromosome is inverted on the samechromosome so the genes on that segment are in a differentlocationInsertion– a part of a chromosome is inserted onto anotherchromosomeTranslocation– part of a chromosome is translocated to theend of another chromosome.Another way that genetic material can be altered is bytransposons. These are jumping genes that can move fromone location to another. These transposable elements can beexcised by an enzyme called transposase. Removing thetransposon may affect the transcription or function of thegene.Watch the following video on Mutations in DNA:NondisjunctionNondisjunction is an error that occurs in meiosis. When individual chromosomes are moving to different cells, entirechromosomes can move to the wrong daughter cell. The resulting egg or sperm cells may be missing a chromosome orhave an extra chromosome. Recall that one chromosome may carry hundreds of genes. The resulting disorder is

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