chapter 12.4 gene regulation & mutation

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