Post on 11-May-2015
12.4 Gene Regulation & Mutation- Pgs.342-349
Gene Regulation- ability of an organism to control which genes are transcribed in response to the environment.
Prokaryotes use operons. Operons- section of DNA that contains
genes for the proteins needed for a specific pathway. Ex: trp operon- tryptophan
lac operon- lactose
Gene Regulation is crucial during development of Eukaryotes. Homeobox (Hox) genes determines the body plan of an organism.
Mutation- mistake or change in the DNA sequence (gene)
It causes a change in the protein it codes for See table 12.3, p. 346 for a complete list.
Gene Mutations Point mutations – mistake with 1 nucleotide
Substitution of the wrong nucleotide in place of correct one
Frameshift mutations – occur when a nucleotide is either inserted or deleted, altering the codon sequence More severe than point mutations because it affects
all of the amino acids in the protein
Causes of MutationsMutagen – any agent that causes a
change in DNADNA polymerase sometimes adds
wrong nucleotides (only 1/100,000) and goes unfixed in 1/1 billion
Environmental Factors
x-rays ultraviolet light radioactive substances certain chemicals (asbestos,
formaldehyde, benzene) high temperatures
Mutations in sex cells Passed on to offspring & will be present
in every cell of the offspring Could result in a new trait or in a protein
that does not function properly
Mutations in body cells Impairs the function of that cell As that cell divides, the mutation will be
passed on to the new cells If it affects the genes that control
division, cells can multiply rapidly-resulting in cancer
QUIZIdentify the following processes as transcription, replication, translation, or mutation.
Name the process below.
mutation
Name the process below.
DNA replication
Name the process below.
Transcription
Name the process below.
Translation