Ch. 11
What are the two essential functions of DNA?
• What is the central dogma of genetics?
• What is meant by the term gene expression?
o Are all genes in a cell expressed at all times?
o What is the difference between a constitutive geneand a regulated gene?
• Explain the difference between genotype and phenotype.
o Is phenotype solely a result of genotype? Explain.
• Why is DNA replication described as semi-conservative?
• What is an origin of replication?
o Distinguish between prokaryotes and eukaryotes in terms of how many origins of replication the chromosomes have.
• Why are topoisomerases needed for replication?
• Describe the function of each of the following enzymes in DNA replication:
o Helicase
o Primase
o DNA polymerase
o Ligase
• In what direction does replication occur? (5’ à3’ or 3’ à 5’?)
o During replication, why is one strand called the “leading strand” and the other the “lagging strand?”
▪ What are Okazaki fragments?
▪ What enzyme joins Okazaki fragments together?
• What do we mean when we say DNA polymerases have “proofreading ability?”
o Why is it important for the DNA polymerase to “proofread” its work?
• Topoisomerase IV is a type of topoisomerase specifically found in prokaryotes. Why do these cells need this enzyme?
• What is the purpose of transcription?
• What role does the promoter serve during transcription?
o Where is the promoter found in relation to the gene?
• Which enzyme is the key enzyme needed to produce mRNA?
• Where does transcription occur in:
o Eukaryotic cells?
o Prokaryotic cells?
• In what direction does transcription occur? (5’ à3’ or 3’ à5’?)
• During transcription, why is one strand of DNA considered the “coding” (or “sense”) strand, and the other the “template” (or “antisense”) strand?
• During transcription, which nucleotide pairs with adenine (A)?
• How does RNA polymerase “know” when it has reached the end of a gene?
• What is the purpose of translation?
• What two types of RNA are needed for translation, in addition to mRNA?
o Describe the role of each.
• What is a codon?
• How many different codons are there?
o How many of these are:
▪ Sense codons
▪ Nonsense (stop) codons
▪ Start codons
• What do we mean when we say the genetic code is:
o Universal
o Triplet
o Overlapping
• Understand how to read a codon chart.
• Describe some ways in which transcription and translation in prokaryotes differs from eukaryotes.
• What is a mutation?
o Are mutations always bad? Explain.
o What is the difference between a spontaneous mutation and an induced mutation?
o What is a mutagen?
▪ Why are many mutagens also called carcinogens?
• What is a:
o Point mutation?
o Insertion?
o Deletion?
• What happens with a:
o Missense mutation?
o Silent mutation?
o Nonsense mutation?
o Frameshift mutation?
• What is horizontal gene transfer?
o Why is horizontal gene transfer especially important in prokaryotes?
• For each of the following types of horizontal gene transfer, where is the foreign DNA coming from?
o Transformation
o Conjugation
▪ What cellular appendage is needed for conjugation?
o Transduction
▪ What acts as the “delivery vehicle” during transduction?
• What is a transposon?
o Why are transposons also called “jumping genes?”
o Which scientist discovered transposons?
o What are two possible effects a transposon could have on a cell?
• What is an operon?
o Do all cells have operons? If not, which types of cells do?
o In an operon, what is the function of an operator?
▪ Where is the operator found?
o In the lac operon, what role does the repressor serve?
▪ What will cause the repressor to be released from the DNA?
▪ What will happen to the operon when the amount of lactose in the cell goes back down?