Mutations and Cancer

Mutation

Changes in the genetic material of a cell

• may occur in gametes and somatic cells

• in coding regions of a gene can affect the amino acid sequence of a protein

• In noncoding regions may influence the phenotype of an organism

Point Mutations (small scale)

changes in just one base pair of a gene

• nucleotide pair substitutions

• one or more nucleotide pair insertions or deletions

Missense Mutations

code for an amino acid, but not the correct amino acid (sickle cell anemia)

Nonsense Mutations

change an amino acid codon into a stop, seriously affects proteins (Duchenne Muscular Dystrophy)

Silent Mutations

have no effect on amino acid, codes for same amino acid, no effect on protein

Chromosomal mutations (large scale)

extensive changes in DNA

Insertions and Deletions

additions or losses of nucleotide pairs in a gene

• disastrous effect on the resulting protein more often than substitution does

• produce a frameshift mutation (Tay Sachs disease)

Causes of Mutations

spontaneous mutations can occur during DNA replication, recombination, or repair

• induced mutations result from external mutagens

Mutagen

physical or chemical agents that can cause mutations

Effects of mutations

• can be beneficial, neutral, and harmful

• the driving force behind evolution and genetic variation

Cancer

a disease that results from alterations in the ways that cells divide

• can be caused by mutations to genes that regulate cell growth and divisions

Genes associated with cancer

Proto-oncogenes

Oncogenes

Tumor suppressor geens

Proto-oncogenes

responsible for normal cell growth and division

Oncogenes

cancer causing

Tumor suppressor genes

encodes proteins that prevents uncontrolled cell growth

• repaired damaged cells

• triggers apoptosis in cells that cannot be replaced

• if genes are mutated, their proteins products often fail to trigger the necessary cell growth inhibition pathways, leading to cancer

Oncogenes improperly…

stimulate cell division even in the absence of growth factors

• can promote promote cancer formation

Mutated gene is…

inherited from parent

• may be due to errors in DNA replication