BIOL 1030H Lecture Notes - Lecture 8: Transposable Element, Dna Replication, Germ Cell
13 May 2018
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DNA Mutation and Repair
Mutation
Any heritable change in the genetic material
There are exceptions
●Exceptions to the 10–10 average in DNA replication
○Certain nucleotides are prone to mutation (hotspots)
○ Differences between the sexes
Rate of mutation depends on cell type
●Somatic cells: cells of the body
●Germ cells: reproductive cells
Somatic Mutation and Cancer
●The accumulation of three successive mutations in a lineage of colon cells results in
malignant colon cancer.
How do mutations arise?
●By chance, this colony contains a few mutant cells.
●The sterile velvet template picks up both mutant and non mutant cells.
●Only the mutant cells grow on selective medium; the position of the colony tells you
which colony on the nonselective medium contains the mutant cells.
Point Mutation
●A G is erroneously incorporated into the daughter strand opposite the T and is not
corrected by the proofreading function.
●In the next round of replication, the G specifies a C in the opposite strand. The new C–G
pair is replicated as faithfully as the original T–A pair and the mutation is now present in
this cell lineage.
Transposable Elements
●Transposable elements can disrupt the normal function of a gene
●When a transposable element is removed, the function of the original gene (dark blue)
can be restored.
Document Summary
Exceptions to the 10 10 average in dna replication. Certain nucleotides are prone to mutation (hotspots) The accumulation of three successive mutations in a lineage of colon cells results in malignant colon cancer. By chance, this colony contains a few mutant cells. The sterile velvet template picks up both mutant and non mutant cells. Only the mutant cells grow on selective medium; the position of the colony tells you which colony on the nonselective medium contains the mutant cells. A g is erroneously incorporated into the daughter strand opposite the t and is not corrected by the proofreading function. In the next round of replication, the g specifies a c in the opposite strand. The new c g pair is replicated as faithfully as the original t a pair and the mutation is now present in this cell lineage. Transposable elements can disrupt the normal function of a gene.
