Mitochondrial DNA & Mutations PDF

Mitochondrial DNA Mitochondrial DNA (mtDNA) is a short genome found in the mitochondria This may be a holdover from a time where mitochondria may have been free-living organisms mtDNA is always identical between mother and child, and can therefore be used to trace maternal lineage Why? FYI Mutatio...

Mitochondrial DNA Mitochondrial DNA (mtDNA) is a short genome found in the mitochondria This may be a holdover from a time where mitochondria may have been free-living organisms mtDNA is always identical between mother and child, and can therefore be used to trace maternal lineage Why? FYI Mutations Genomes are not constant Mutations occur from time to time Mutations occurring in body cells are called somatic cell mutations However, only mutations occurring in reproductive cells (germ line mutations) will be passed on to offspring Causes of Mutations Some mutations occur naturally (spontaneous mutations) These mutations may be caused by incorrect base pairing by DNA polymerase during replication Mutagens: Substances that cause mutations See handout p. 12-14– types of mutations Mutations and Variation Genetic variation is a result of mutations This is because changes in the DNA are the only source of variation at a heritable level This variation can eventually become an adaptation if there is a change in the environment that favors that new variation Errors and Mutations FYI: If there are 3 billion base pairs in the DNA of each of your cells, even 1 mistake in 1000 could cause up to 3,000,000 mutations during each replication However, mistakes in duplicating DNA are very infrequent This is because “proofreading” enzymes look for mismatched base pairs and make repairs Oncogenes FYI most cancer cells show nitrogen base substitution Oncogenes: cancer-causing genes; seem to turn on cell division the oncogenes seem to be present in normal DNA strands, but they are not abnormally active unless they mutate the most common oncogene, ras, is found in 50% of colon cancer cases and 30% of lung cancer cases Ras makes a protein that acts as a “on” switch for cellular division however, the oncogene produces a protein that prevents this gene from turning “off” this may occur if the regulator and structural genes, which are normally adjacent to each other, are separated Gene Recombination Recombinant DNA technology- tools and techniques that manipulate the genes of an organism. In a laboratory, restriction and ligase enzymes can be used to put genes into small organisms such as bacteria or yeast to study individual genes  Restriction Enzymes (Endonucleases) Restriction enzymes: (such as Eco R1), cut up DNA at specific sites These sites have “sticky ends” (single strands) which tend to bond with “sticky ends” that are created by other restriction enzymes