DNA Mutations Mutations are changes to the genetic information of the cell. There are 2 different types of mutations – Drives evolution – Most are silent Most that affect gene product are not viable (end in spontaneous abortion or with the offspring dying young)

Addition of chromosomes or Large pieces of chromosomes Deletions – section is lost Inversions – section is flipped Translocations – section is attached to another chromosome Polyploidy – an entire extra chromosome or set of chromosomes – More survivable in plants (3N, 4N, …) – Down Syndrome (trisomy 21) 3 copies of chromosome 21

Point Mutations point mutations – single nucleotide – Each mutation carries with it the ability to alter the phenotype of the individual and, if in the cells that create the gametes, all the offspring of the individual. – base-pair substitutions silent mutation - substitution that leads to the same AA missense mutation - change in a base pair that leads to a new AA nonsense mutation - changes an AA to a stop Insertions & Deletions – lead to frame shifts if the insertion or deletion if it is in an exon these mutations are almost always disastrous to the protein being formed as it changes all codons down stream

Mutagens physical and chemical agents that cause a change in DNA – physical - radiation – chemical - classified as carcinogens Teratogen – leading to birth defects of the fetus

Lac Operon Concept works by the process of feedback inhibition – product of the reaction blocks a step in the metabolic pathway leading to the product shuts off the production at the DNA level - inhibits the production of mRNA saves resources of the organism

Operons switch is called the operator – located within the promoter region – can be switched off by the presence of a repressor bound to the operator blocks attachment of the RNA Pol Repressors are reversible – the presence of an inducer inactivates repressor ex: lactose – binds to the repressor changing its conformation

Eukaryotic Gene Regulation The entire genome of the eukaryotic organism is present in every cell of the organism. Although all genes are present, the numbers and types that are actively transcribed can be managed through the processing and packaging of the DNA.

Regulation of Gene Expression Regulation of Chromatin Structure – histone modifications acetylation (-COOH 3 ) of the histone tails makes the chromatin to be less dense and promotes transcription – inhibits binding of the histone to neighboring histone complexes – DNA methylation addition of a methyl group (-CH 3 ) to DNA (mostly cytosine) inactivates the DNA method for inactivating the extra X chromosomes in females methylation patterns are passed with each cell division – called genomic imprinting