O blood is recessive to AB blood. What possible blood types could result from parents with O and AB Blood?

Why do we perceive objects as retaining their brightness under different lighting levels?

Why has two different alleles for the same trait?

Pls me i need this ! each cell has genes activated depending on it's job and what kind of cell it is. it is the presence of that causes the repressor protein to fall off and unblock the gene on the lac operon. if a gene is turned on then it is being an additional circular chromosome found in some bacteria that is used in genetic engineering.