Gene regulation

How does DNA make different cells?All cells have a full set of DNANot all the DNA is expressed in each onePromoters and repressors allow only certain genes to be expressed (make protein)Nerve, cardiac, muscle, white blood cells

The gene that breaks down lactose is repressed

How it worksWhen lactose is added, it binds to the repressor protein.

ActivationWhen lactose binds to the repressor, it movesaway, allowing the protein to be madeLeft side: why do you think this process is called a positive feedback loop?

Eukaryotic Gene RegulationMany eukaryotic genes have a sequence called the TATA box that helps to position RNA polymerase.Direction of transcription

DifferentiationFrom a fertilized egg to an adult, cells grow and divide.They also differentiate into many different types of cellsHox genes control that differentiation They are inherited from the genes of our common ancestors

Gene mutation Point mutation: the subtraction, addition or substitution of a single nucleotide Changing a nucleotide will change the codonCan change the amino acid Subtraction and addition can cause a Frame shift making all amino acids downstream change This can completely change a protein Most mutations are harmfulLeft side: why dont all mutations causes changes to the amino acids?

Not all mutations are equalIf you put a hox gene for eye from a fruit fly into a mouse embryo, it will develop into an mouse eye.If you move a hox gene for an eye from the head to the back of a fruit fly embryo the eye will develop on the backSmall genetic changes can make large changes to an organism.

Summaryreview What do hox genes do?What are repressors and promoters?What causes a frame shift?

*The lac genes in E. coli are turned off by repressors and turned on by the presence of lactose. When lactose is not present, the repressor binds to the operator region, preventing RNA polymerase from beginning transcription. Lactose causes the repressor to be released from the operator region.*Many eukaryotic genes include a sequence called the TATA box that may help position RNA polymerase. Eukaryotic genes have regulatory sequences that are more complex than prokaryotic genes.