Gene Expression
Where in a eukaryotic cell does transcription occur?
nucleus
What DNA region does RNA polymerase bind to start transcription?
promoter
A mutation that changes one amino acid is called what?
missense
What molecule is commonly used as a vector to transfer genes into bacteria?
plasmid
What enzyme unwinds the DNA double helix at the replication fork?
Helicase
What enzyme synthesizes RNA during transcription?
RNA polymerase
In the lac operon, is the operon on or off when lactose is present?
on
Which type of mutation often causes the greatest change to a protein, substitution or frameshift?
frameshift
Why are bacteria treated with heat shock or chemicals during plasmid uptake?
To make the cell membrane permeable so plasmids can enter
Which enzyme adds complementary nucleotides to the growing DNA strand?
DNA polymerase III
Name two modifications that occur to pre mRNA before translation.
any two, splicing, 5 prime cap, poly A tail
What protein blocks transcription by binding the operator?
repressor
If a stop codon forms early, what type of mutation occurred?
nonsense
What enzyme joins DNA fragments together?
DNA Ligase
Why is an RNA primer required for DNA replication?
DNA polymerase can only add nucleotides to an existing strand and cannot start a strand on its own
Explain why introns are removed before translation.
introns are noncoding and must be removed so the correct amino acid sequence is produced
Predict what happens to gene expression if a repressor protein cannot bind the operator.
transcription occurs continuously
A three nucleotide insertion occurs. Predict the effect on the protein.
one extra amino acid added but reading frame stays the same
Why are antibiotic resistance genes included in plasmids used for transformation?
to select bacteria that successfully took up the plasmid
Explain why the lagging strand is synthesized in short fragments instead of continuously.
DNA polymerase adds nucleotides only 5 prime to 3 prime, so the strand made away from the replication fork must be built in Okazaki fragments
A cell produces large amounts of mRNA but very little protein. Identify one likely step being regulated and explain.
translation or post transcriptional regulation, ribosome binding or miRNA blocking translation
Compare gene regulation in prokaryotes and eukaryotes with one difference.
operons in prokaryotes vs individual genes and transcription factors/chromatin control in eukaryotes
Explain why two different DNA mutations can produce the same protein.
redundancy of genetic code, multiple codons code for same amino acid
Describe one real world application of recombinant DNA technology.
insulin production, gene therapy, GM crops, vaccines
A mutation reduces DNA ligase activity. Predict the effect on DNA replication and explain.
Okazaki fragments would not be joined, leaving gaps in the sugar phosphate backbone and producing incomplete DNA strands