Prepare for AP Biology gene expression questions with these practice answers. This covers transcription, translation, gene regulation, and control mechanisms.
Q: gene regulation
Answer: the turning on and off of genes
Q: gene expression
Answer: the overall process by which genetic information flows from genes to proteins/genotype to phenotype
Q: promoter
Answer: a site where the transcription enzyme, RNA polymerase, attaches and initates transcription, determines which of the two strands of the DNA double helix is used as the template in trascription
Q: operator
Answer: DNA control sequence, acts as a switch, determines whether RNA polymerase can attach to the promoter and start transcribing the gene
Q: operon
Answer: cluster of genes with related functions, exist ONLY in prokaryotes
Q: repressor
Answer: protein that turns off transcription, functions by binding to the operator and physically blocking the attachment of RNA polymerase to the promoter
Q: regulatory gene
Answer: located outside the operon, codes for the repressor
Q: activators
Answer: proteins that turn operons on by binding to DNA, make it easier for RNA polymerase to bind to the promoter
Q: differentiation
Answer: process by which individual cells specialize in structure and function
Q: histones
Answer: crucial aspect of DNA packing, account for about half the mass of eukaryotic chromosomes –> small proteins grouped and wrapped around a DNA strand to form a nucleosome
Q: nucleosome
Answer: consists of DNA wound around a protein core of 8 histone molecules
Q: epigenetic inheritance
Answer: inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
Q: X chromosome inactivation
Answer: initiated early in embryonic development, when two X chromosomes in each somatic cell is inactivated at random
Q: Barr body
Answer: compact object of the inactive X in each cell of a female
Q: transcription factors
Answer: eukaryotic RNA polymerase requires the assistance of these proteins, such as activator proteins
Q: enhancers
Answer: DNA control sequences, part of the first step in initiating gene transcription –> binding of activator proteins to these
Q: microRNAs (miRNAs)
Answer: small RNA molecules that can bind to complementary sequences on mRNA molecules
Q: RNA interference (RNAi)
Answer: procedure that involves injecting miRNa into a cell that can turn off expression of a gene with a sequence that matches the miRNA
Q: homoeotic gene
Answer: master control gene that regulates batteries of other genes that actually determine the anatomy of parts of the body
Q: DNA microarray
Answer: glass slide with tiny amounts of thousands of different single-stranded DNA fragments fixed to it in tiny wells in tightly spaced array or grid, used for genome wide expression studies
Q: signal transduction pathway
Answer: series of molecular changes that converts a signal on a target cell’s surface to a specific respone inside the cell
Q: reproductive cloning
Answer: results in the birth of a new living individual, cloning type
Q: embryonic stem cells
Answer: harvested from the blastocyst, easily perpetuate themselves indefinitely
Q: therapeutic cloning
Answer: producing embryonic stem cells for therapeutic treatments
Q: adult stem cells
Answer: able to give rise to many but not all cell types in contrast to embryonic stem cells
Q: oncogene
Answer: can cause cancer when present in a single copy in the cell
Q: proto-oncogene
Answer: normal gene that has the potential to become an oncogene
Q: tumor-suppressor genes
Answer: proteins they encode help prevent uncontrolled cell growth/tumors
Q: recombinant DNA
Answer: formed when scientists combine nucleotide sequences (pieces of DNA) from two different sources to form a single DNA molecule
Q: plasmid
Answer: small, circular DNA molecule that replicate and duplicate separately and independently from the much larger bacterial chromosome
Q: gene cloning
Answer: the production of multiple identical copies of a gene-carrying piece of DNA
Q: vector
Answer: gene carrier
Q: restriction enzymes
Answer: enzyme cutting tools used to cut and paste DNA
Q: restriction site
Answer: a DNA sequence recognized by a particular enzyme
Q: genomic library
Answer: the entire collection of all the cloned DNA fragments in a genome
Q: reverse transcriptase
Answer: enzyme used by retroviruses to catalyze the synthesis of DNA on an RNA template
Q: complementary DNA (cDNA)
Answer: the double stranded DNA that results from reverse transcriptase, represents only the subset of genes that had been transcribed into mRNA in the starting cells
Q: nucleic acid probe
Answer: used to find a specific gene or other nucleotide sequence within a mass of DNA
Q: genetically modified organisms
Answer: organisms that have acquired one or more genes by artificial means
Q: transgenic organism
Answer: organism that has newly acquired gene/s from another organism, typically of another species
Q: Ti plasmid
Answer: the msot common vector/plasmid used to introduce new genes into plant cells
Q: gene therapy
Answer: alteration of an afflicted individual’s genes for therapeutic purposes, used to treat a variety of diseases
Q: DNA profiling
Answer: the analysis of DNA samples to determine whether they came from the same individual, used in forensics
Q: polymerase chain reaction
Answer: gtechnique by which a specific segment of a DNA molecule can be targeted and quickly amplified in the laboratory
Q: gel electrophoresis
Answer: sorts DNA molecules by size, thin slab made of agarose acts a molecular sieve that separates macromolecules (usually proteins or nucleic acids) on the basis of size, electrical charge, or other physical properties
Q: repetitive DNA
Answer: consists of nucleotide sequences that are present in multiple copies in the genome, much of the DNA that lies between genes in humans is of this type
Q: short tandem repeat (STR)
Answer: for DNA profiling, a series of short DNA sequences that are repeated many times in a row in the genome
Q: STR analysis
Answer: a method of DNA profiling that compares the lengths of STR sequences at specific sites in the genome, also compares the number of repeats of specific four-nucleotide DNA sequences at 13 sites scattered throughout the genome
Q: single nucleotide polymorphism (SNP)
Answer: a one-nucleotide variation in DNA sequence found within the genomes of at least 1% of a polymorphism
Q: restriction fragment length polymorphism (RFLP)
Answer: variation in the lenght of a restriction fragment, produced when homologous DNA sequences containing SNPs are cut up with restriction fragments
Q: polymorphism
Answer: DNA sequence at a specific place on a chromosome exhibits small nucleotide differences
Q: whole-genome shotgun method
Answer: a method for determining the DNA sequence of an entire genome –> after a genome is cut into small fragments, each fragment is sequenced and then placed in the proper order
Q: transcription
Answer: the synthesis of RNA under the direction of DNA
Q: translation
Answer: the synthesis of protein under the direction of RNA
Q: triplet code
Answer: a set of three-nucleotide-long “words” that specify the amino acids for polypetide chains
Q: codons
Answer: the genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as a series of nonoverlapping three-base “words”
Q: genetic code
Answer: the set of rules that relate codons in RNA to amino acid in proteins
Q: RNA polymerase
Answer: transcription enzyme, links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template
Q: terminator
Answer: third phase of transcription (termination), sequence of bases in the DNA template that signals the end of the gene
Q: messenger RNA (mRNA)
Answer: the type of ribonucleic acid that encodes the genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences
Q: introns
Answer: internal non-coding regions
Q: exons
Answer: coding regions, the parts of a gene that are expressed
Q: RNA splicing
Answer: the removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequence, occurs before mRNA leaves the nucleus
Q: transfer RNA (tRNA)
Answer: a type of ribonucleic acid that functions as an interpreter in translation –> each molecule has an anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA
Q: anticodon
Answer: on a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA
Q: ribosomes
Answer: structures in the cytoplasm that position mRNA and tRNA close together and catalyze the synthesis of polypeptides
Q: ribosomal RNA (rRNA)
Answer: a type of ribonucleic acid consisting of nucleotide monomers with a ribose suger and the nitrogenous bases A, C, G, U; usually single-stranded, fuctions in protein synthesis, gene regulation
Q: start codon
Answer: specific codon that an mRNA molecule binds to where translation is to begin on the mRNA molecule
Q: P site
Answer: tRNA binding site, hold the growing polypeptide during translation
Q: A site
Answer: tRNA binding site, vacant and ready for the next amino-acid-bearing tRNA
Q: codon recognation
Answer: TRANSLATION: the anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome
Q: peptide bond formation
Answer: TRANSLATION: the polypeptide separates from the tRNA in the P site and attaches by a new peptide bond to the amino acid carried by the tRNA in the A site –> the ribosome catalyzes formation of the peptide bond, adding one more amino acid to the growing polypeptide chian
Q: translocation
Answer: TRANSLATION: the P site tRNA now leaves the ribosome and the ribosome translocates/moves the remaining tRNA in the A site, with the growing polypeptide, to the P site –> codon and anticodon remain hydrogen bonded and the mRNA and tRNA move as a unit –> movement brings into the A site the next mRNA codon to be translated
Q: stop codon
Answer: in mRNA, one of the tree triplets (UAG, UAA, UGA) that signal gene translation to stop
Q: mutation
Answer: any change in the nucleotide sequence of DNA, can involve large regions of a chromosome or just a single nucleotide pair
Q: silent mutation
Answer: a mutation in a gene that changes a codon to one that encodes for the same amino acid as the original codon –> the amino acid sequence of the resulting polypeptide is thus unchanged
Q: missense mutation
Answer: a change in the nucleotide sequence of a gene that alters the amino acid seqeunce of the resulting polypeptide –> a codon is changed from encoding one amino acid to encoding a different amino acid
Q: nonsense mutation
Answer: a change in the nucleotide sequence of a gene that converts an amino-acid-encoding codon to a stop codon –> results in a shortened polypeptide
Q: mutagenesis
Answer: the production of mutations
Q: mutagens
Answer: physical or chemical agents that cause mutations
Q: capsid
Answer: protein coat that envelopes nucleic acid, surrounds the virus
Q: virus
Answer: an infectious particle consisting of a bit of nucleic acid wrapped in a protein coat (capsid), parasites that can replicate only inside cells
Q: lytic cycle
Answer: a type of viral replication cycle that results in the release of new viruses by lysis (breaking open) of the host cell
Q: lysogenic cycle
Answer: a type of bacterial replication cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage –> new phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome
Q: prophage
Answer: phage DNA that has been inserted by genetic recombination into the DNA of a bacterial chromosme
Q: retrovirus
Answer: an RNA virus that reproduces by means of a DNA molecule –> reverse-transcribes its RNA into DNA, inserts DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNAex: HIV and cancer-causing viruses
Q: viroids
Answer: small circular RNA molecules that infect plants
Q: prions
Answer: infectious proteins that are formidable pathogens in plants and animals
Q: transformation
Answer: the incorporation of new genes into a cell from DNA that the cell takes up from the surrounding environment
Q: transduction
Answer: the transfer of bacterial gnes from one bacterial to another by a phage
Q: conjugation
Answer: the union/mating of two bacterial cells or protist cells and the transfer of DNA between them