Transcript Gene regulation - Sonoma Valley High Home
Gene regulation How does DNA make different cells? • All cells have a full set of DNA • Not all the DNA is expressed in each one • Promoters 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 works • When lactose is added, it binds to the repressor protein. Activation Left side: why do you think this process is called a “positive” feedback loop? When lactose binds to the repressor, it moves away, allowing the protein to be made Eukaryotic Gene Regulation • Many eukaryotic genes have a sequence called the TATA box that helps to position RNA polymerase. Direction of transcription Differentiation • From a fertilized egg to an adult, cells grow and divide. • They also differentiate into many different types of cells • Hox 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 codon – Can 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 harmful Left side: why don’t all mutations causes changes to the amino acids? Not all mutations are equal • If 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 back • Small genetic changes can make large changes to an organism. Summary review 1. What do hox genes do? 2. What are repressors and promoters? 3. What causes a frame shift?