DNA and Mutations
Occurrence of mutation.
Mutation is the process that produces a gene or a chromosome set different from the wild type. For instance this allows us to measure the frequency of mutation occurance.a cell caring mutation can be used as probes to disassemble the constituent parts of a biological function and to examine their workings and interrelations.For a recessive mutation to give rise to a mutant phenotype in a diploid organism both alleles must carry the mutation but one copy of dominant mutation allele leads to a mutant phenotype.
For a recessive mutation it results to loss of function whereas the dominant mutation results in a gain of function.
Causes of mutation.
Mutations can arise in cells of all types as a result of a variety of factors: chance, spontaneous events during replication, excess flexibility of the DNA strand and the subsequent misparing of bases, environmental expose to certain chemical, ultraviolet radiation or other external factors can also cause DNA to change.Mode of DNA replication: meselson stahl experiment. There are three basic models for DNA replication, Semi-conservative replication. In this model, the two strands of DNA unwind from each other, and each acts as a template for synthesis of a new, complementary strand. This results in two DNA molecules with one original strand and one new strand.
In this model, DNA replication results in one molecule that consists of both original DNA strands (identical to the original DNA molecule) and another molecule that consists of two new strands (with exactly the same sequences as the original molecule).
In the dispersive model, DNA replication results in two DNA molecules that are mixtures.