DNA Replication (16)
Gene Expression (17)
Gene Regulation (18)
Viruses (19)
Biotechnology (20)
100
Enzyme that relieves over-winding strain ahead of replication forks by breaking, swiveling, and rejoining DNA strands
Topoisomerase
100
Why is the genetic code redundant but not ambiguous?
Redundant because more that one codon can code for an amino acid
NOT ambiguous because one codon CANNOT code for more than one amino acid
100
What is an operon? Where can operons be found?
An operon is the entire stretch of DNA that includes the operator, the promoter, and the genes that they control- **Only found in prokaryotes
100
Are viruses living organisms? Why or why not?
Not living
Cannot exist independently from the host cell
Cannot reproduce or carry out metabolic activities outside of a host cell
Does NOT mean lifeless
100
What is the difference between "in vivo" and "in vitro?"
In vivo: in the body
Experiments performed within a natural organism, in conditions that precisely mirror those existing in nature
In vitro: in glass
Experiments performed in artificial, simplified conditions
200
What are Okazaki fragnents?
short fragment of DNA synthesized on the lagging strand during DNA replication.
200
What does it mean for the genetic code to be universal?
shared by the simplest bacteria and the most complex plants and animals- Common ancestors
200
What kind of operon is the Trp operon? Why is this?
Repressible operon because it is always "on" unless turned "off"
When tryptophan is present, it binds to the trp repressor protein, which turns the operon off
The repressor is active only in the presence of its co-repressor tryptophan; thus the trp operon is turned off (repressed) if tryptophan levels are high
200
What kind of genomes can viruses have?
• Double- or single-stranded DNA (DNA virus) or
• Double- or single-stranded RNA (RNA virus)
200
What is a plasmid?
Tiny circular DNA molecule with only a few genes
Extra “bag of goodies”
Can carry foreign DNA into host cell and replicate
From book:
"A small, circular, double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome; in DNA cloning, plasmids are used as vectors carrying up to about 10,000 base pairs (10 kb) of DNA. Plasmids are also found in some eukaryotes, such as yeasts."
300
What does DNA Ligase do?
Joins Okazaki fragments on lagging strand
Joins 3' end of DNA that replaced primer on leading strand to rest of leading strand
300
What are the three stages of transcription?
Initiation: transcription factors bind to promoter, enabling RNA polymerase to bind to promoter. Transcription initiation complex forms
Elongation: Nucleotides are added to RNA transcript at 3` end. RNA strand lengthens
Termination: terminator sequence: TTATTT (AAUAAA in mRNA strand, triggers polymerase to detach from the DNA and release the mRNA strand)
300
What kind of operon is the lac operon? Why?
lac operon is an inducible operon
lac repressor is active and switches the lac operon off
A molecule called an inducer inactivates the repressor to turn the lac operon on
300
What can hosts provide viruses with?
nucleotides, enzymes, ribosomes, tRNAs, amino acids, ATP
DNA polymerase if virus has DNA genome, if RNA genome, viruses have own polymerases that can use RNA as a template
300
What is in vitro mutagenesis and what is it used for?
a cloned gene is mutated, then returned to cell (“knocks out” normal gene and may reveal gene function)
400
What are telomeres?
a region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes
400
Draw and label a translational initiation complex. What are the 3 sites for?
A site: holds the tRNA that carries the next amino acid to be added to the chain (ACCESS)
P site: holds the tRNA that carries the growing polypeptide chain (PEPTIDE)
E site: the exit site, where discharged tRNAs leave the ribosome (EXIT)
Anticodon: complementary to codon for the specific amino acid on tRNA (3' --> 5')
400
What is determination in embryonic development?
Determination: irreversibly commits a cell to becoming a particular cell type
Key to determination is the activation of “master regulatory genes
400
What happens in the Lysogenic cycle of a phage?
Viral DNA is incorporated into the bacterial chromosome and is copied with bacterial DNA. Prophage will exit bacterial chromosome and induce lytic cycle, where phage DNA and proteins are synthesized and assembled. Cell lyses and phages released
400
What is Polymerase Chain Reaction (PCR) and what does it do?
Amplifies a gene you are interested in
Multiple repetitions of a three-step cycle brings about a chain reaction that produces an exponentially growing population of identical DNA molecules
500
What end of DNA can DNA Polymerase attach nucleotides to?
In what direction is DNA synthesized?
Attaches nucleotides to 3' end
DNA synthesized 5' --> 3'
500
What is a nonsense mutation?
Mutation that results in an early stop codon in an RNA sequence, resulting in an incomplete protein
500
A cancerous cell is usually characterized by
at least one active oncogene and the mutation of several tumor-suppressor genes
500
What are prions?
An infectious agent that is a misfolded version of a normal cellular protein. Prions appear to increase in number by converting correctly folded versions of the protein to more prions.
degenerate brain disorders (ex: mad cow disease)
500
What is a sticky end?
A single-stranded end of a double-stranded restriction fragment (longer than other complementary).
Due to restriction enzymes (endonucleases) recognize a specific sequence in DNA and cut it at that exact sequence. Typically done for insertion of fragment of DNA from another source to make a recombinant DNA molecule