Module 7
1. Module 7
1.16. Page 4
Module 7—Molecular Genetics: DNA, RNA, and Protein Synthesis
Lesson Summary
This lesson addressed the following focusing questions:
- What kinds of changes in DNA can result in variation?
- How can mutations in DNA have both a positive and a negative result?
- What are the causes of changes in DNA?
What is a mutant? You should now realize that everyone’s DNA is constantly changing. Can we all be considered mutants? Most of the changes or mutations have no effect on us at all, but others may have minimal or even dramatic effects on our lives. 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, thus causing a new variation in the population. These variations can have a positive outcome and can give an advantage to a population, as with sickle cell anemia’s protection against malaria, or they could have a negative affect and can disadvantage a population, as with cancer.
Mutations that can occur may be point mutations and chromosomal mutations. Point mutations involve substitution, insertion, or deletion of one or more nucleotides. Chromosomal mutations involve entire sections of the chromosome in which sections can be lost or rearranged.
Lesson Glossary
Consult the glossary in the textbook for other definitions that you may need to complete your work.
adaptive advantage: a difference in structure, physiology, or behaviour that gives an organism a better chance of survival
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 (e.g., nitrites)
chromosomal mutation: mutation that involves the deletion, insertion, or 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
gene pool: the total of all the alleles of all genes in the individuals in a population
germ line mutation: mutation that occurs on a gamete and can be passed to the next generation
induced mutation: permanent change in genetic material caused by a mutagen outside the cell
insertion: a type of point mutation in which one nucleotide is added to the DNA sequence, causing a frameshift mutation
mutagen: substance or event that increases the rate of mutation in an organism
mutation: a permanent change in the genetic code (DNA) of a cell
physical mutagen: agent that can forcibly break a nucleotide sequence, causing random changes in one or both strands of a DNA molecule (e.g., X-rays)
point mutation: permanent change in the genetic material of a cell that affects one or just a few nucleotides
somatic cell mutation: mutation that occurs in a body cell; passed on to daughter cells, but not to the next generation of individual organisms
substitution: a type of point mutation in which one nucleotide is switched for another nucleotide in a DNA sequence