CAMPBELL-BIOLOGY CHAPTER 18 EXAM Q’S AND A’S

CAMPBELL-BIOLOGY CHAPTER 18 EXAM Q’S AND A’S operator - answer- region of DNA within the promoter that controls RNA polymerase's access to a set of genes with related functions operon - answer- a unit of gene regulation and transcription in bacterial DNA that consists of a promoter, an operator, and one or more structural genes repressor - answer- a protein that binds to an operator and physically blocks RNA polymerase from binding to a promoter site. is specific to the operator it binds. regulatory gene - answer- a gene that produces a repressor substance that inhibits an operator trpR - answer- regulatory gene or trp operon; codes for trp repressor that is active when effector is bound and attaches to DNA corepressor - answer- a small molecule that cooperates with a repressor protein to switch an operon off repressible operon - answer- transcription is usually on, but can be inhibited (repressed) when a specific small molecule binds allosterically to a regulatory protein (example tryptophan) inducible operon - answer- usually off, but can be stimulated (induced) when a specific small molecule interacts with a regulatory protein (example lac operon) inducer - answer- A specific small molecule that inactivates the repressor in an operon. allolactose - answer- inducer in LAC operon cAMP - answer- Catabolite repression occurs when its high concentrations accumulate in the cell and interact with catabolite repressor protein. CAP - answer- stimulatory protein, activator of transcription activator - answer- A protein that binds to DNA and stimulates transcription of a specific gene. differential gene expression - answer- The expression of different sets of genes by cells with the same genome. histone acetylation - answer- the attachment of acetyl groups (-COCH3) to certain amino acids of histone proteins, the chromatin becomes less compact, and the DNA is accessible for transcription histone code hypothesis - answer- specific combinations of modifications, rather than the overall level of histone acetylation, help determine the chromatin configuration, influencing transcription. DNA methylation - answer- addition of methyl group to DNA (usually to Cytosine), associated with decreased transcription (permanent deactivation) genomic imprinting - answer- A phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent. epigenetic inheritance - answer- Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence. control elements - answer- Segments of noncoding DNA that help regulate transcription of a gene by binding proteins called transcription factors. specific transcription factors - answer- Increase the level of transcription in certain cell types or in response to signals proximal control elements - answer- Control elements located close to the promoter Still do the same job of binding proteins to DNA so that transcription can take place Increase rate of transcription Distal control elements - answer- Also called enhancers. They are segments of eukaryotic DNA that contain multiple control elements, usually located far from the gene whose transcription is regulated. enhancers - answer- A DNA sequence that recognizes certain transcription factors that can stimulate transcription of nearby genes alternative RNA splicing - answer- different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns proteasome - answer- A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin. protein-coding DNA - answer- ~1.5% of human genome noncoding RNA - answer- ncRNA - forms an extensive and sophisticated genome regulatory network microRNAs - answer- small single stranded RNA molecules that bind to mRNA and can degrade mRNA or block its translation - miRNAs RNA interference - answer- Blocking gene expression by means of an miRNA silencing complex small interfering RNAs - answer- length of 21-23 nucleotides double-stranded inhibit gene expression by degrading homologous mRNA