Karp Cell & Molecular Bio Chapter 12 Exam Questions And Answers(A+ GUARANTEED)

operon - ANSWER- A functional complex of genes encoding enzymes shared by a metabolic pathway. structural genes - ANSWER- code for the enzymes and are translated from a single polycistronic mRNA (encodes for more than one protein). promoter - ANSWER- Binding site for RNA polymerase --transcription. operator - ANSWER- Binding site next to promoter where regulatory proteins bind repressor protein - ANSWER- binds a specific DNA sequence and determines whether or not a particular gene is transcribed. RNA polymerase is unable to bind to the promoter if the repressor is bound regulatory gene - ANSWER- encodes the repressor protein inducible operon - ANSWER- it is turned on by the presence of an inducer the lac operon - ANSWER- contains three structural genes. If lactose is present, it binds the repressor, altering its conformaFon and inhibiFng binding to the operator. the trp operon - ANSWER- represents negative feedback; The trp operon repressor is active only when it is bound to its corepressor tryptophan. repressible operon - ANSWER- it is turned off by the presence of a repressor riboswitches - ANSWER- 5' secondary structure of mRNA; they undergo a conformational change that suppresses either termination of transcription or initiation of translation. nuclear envelope - ANSWER- encloses the contents of the nucleus; two membranes fused at nuclear pores chromatin - ANSWER- extended fibers of this material make up chromosomes nucleolus - ANSWER- where rRNA synthesis takes place in the nucleus nucleoplasm - ANSWER- the fluid in the nucleus where solutes are dissolved nuclear matrix - ANSWER- the protein containing fibrillar network in the nucleus nuclear lamina - ANSWER- supports the nuclear envelope and is composed of IF lamins Nuclear Pore Complex (NPC) - ANSWER- Functions as a hydrophobic pore that blocks diffusion of larger macromolecules nucleoporins - ANSWER- make up the nuclear pore complex nuclear localization signal (nls) - ANSWER- Proteins synthesized in the cytoplasm are targeted for the nucleus by this importin - ANSWER- an NLS receptor that guides proteins into the nucleus exportin - ANSWER- an NLS receptor that guides proteins out of the nucleus histone - ANSWER- protein component of chromosomes nucleosomes - ANSWER- DNA and histones are organized into repeating subunits called core particle - ANSWER- contains octomer of histone molecules; 2 copies each of H2A, H2B, H3, H4 histone H1 - ANSWER- serves as a linker serves as a linker between nucleosomes N-termini - ANSWER- extend out of the nucleosome; are important for modification of DNA packaging cohesin - ANSWER- holds together sister chromatids during meiosis and mitosis; also maintains structure in chromatin loops euchromatin - ANSWER- a dispersed state of chromatin fiber heterochromatin - ANSWER- chromatin fibers that are tightly condensed Constitutive heterochromatin - ANSWER- chromatin that remains condensed all of the time facultative heterochromatin - ANSWER- chromatin that is inactivated during a certain phase of an orgnisms life histone code - ANSWER- accessibility to chromatin regions depends on the amount of chemical modification in histone tails Methylation - ANSWER- makes chromatin more compact and less accessible for transcription