Module 7 Molecular Genetics

Lesson Summary

Mutants, who are they anyway? After going through this lesson you should realize that everyone’s DNA is changing all of the time. Can we all be considered mutants? Most of the changes or mutations have no effect on us at all (as in silent mutations), but some may have minimal or dramatic effects on our lives (as with mis-sense or nonsense mutations). The only mutations that will affect our offspring are mutations that occur in our germ cells. When mutations occur in the germ line, future generations can continue to pass on the mutation causing a new variation in the population. These variations can have positive outcome and give an advantage to a population, as with sickle-cell anemia’s protection against malaria, or they could have a negative affect and disadvantage a population, as with cancer.

Glossary

chemical mutagen: molecule that can enter the cell nucleus and induce a permanent change in the genetic material of the cell by reacting chemically with DNA (eg. Nitrites)

chromosomal mutation: mutation that involves the deletion, insertion, crossing over of chromosomes

deletion: a type of point mutation where a nucleotide is removed from a DNA sequence, causing a frameshift mutation

frameshift mutation: permanent change in the genetic material of a cell caused by the insertion or deletion of one or two nucleotides so that the entire reading frame of the gene is altered

induced mutation: permanent change in genetic material caused by a mutagen outside the cell

insertion: a type of point mutation where a nucleotide is added to the DNA sequence, causing a frameshift mutation

mutagen: substance or event that increases the rate of mutation in an organism

mis-sense mutation: permanent change in the genetic material of a cell that results in a slightly altered but still functional protein

nonsense mutation: permanent change in the genetic material of a cell that renders a gene unable to code for a functional protein

physical mutagen: agent that can forcibly break a nucleotide sequence, causing random changes in one or both strands of a DNA molecule (eg X-rays)

point mutation: permanent change in the genetic material of a cell that affects one or just a few nucleotides

silent mutation: permanent change in the genetic material of a cell that has no effect on the function of the cell

substitution: a type of point mutation where a nucleotide is switched for another nucleotide in a DNA sequence