Exam III Flashcards
List four functions of proteins in cells
- Enzymes that catalyze nearly all chemical reactions in a cell
- Proteins play structural roles acting as the cytoskeleton of cells and as membrane channels that allow molecules or atoms to pass into or out of the cell
- Some toxins made by disease-causing microorganisms are proteins
- Antibiotics made by the human immune system are proteins
Macromolecules that play structural roles acting as the cytoskeleton of cells and as membrane channels that allow molecules or atoms to pass into or out of the cell.
Proteins
Enzymes that catalyze nearly all chemical reactions in a cell are what type of macromolecule?
Proteins
Toxins made by disease-causing microorganisms are what type of macromolecule?
Proteins
Antibiotics made by the human immune system are what type of macromolecule?
Proteins
What type of macromolecule is used as membrane channels?
Protein
Give examples of five functions of proteins in eukaryotes and bacteria.
- Cytoskeleton
- Membrane channels
- Enzymes
- Toxins
- Antibodies
Define a “gene.”
A segment of DNA that codes for a protein or sometimes functional RNA.
What is a segment of DNA that codes for a protein or sometimes functional RNA called?
A gene
Define “gene expression.”
The process of turning the information in a gene into a functional product.
Consists of the processes of transcription and translation.
What is the process of turning the information in a gene into a functional product called?
Gene expression
What process consists of transcription and translation?
Gene expression
What are the two processes involved in gene expression?
Transcription and translation
When DNA is being accessed to code for a protein, what comes first: translation or transcription?
Transcription (“c” comes before “l” in translation)
Define DNA polymerase, focusing on its role in DNA replication.
- DNA polymerase, adds dNTPs to the 3’ end of the newly synthesized DNA chain.
- The dNTP added (either dATP, dTTP, dCTP or dGTP) is the one that base-pairs with the nucleotide on the template strand.
- DNA polymerase pauses every time it adds a nucleotide to double-check if the correct nucleotide is added. If the wrong nucleotide is added, it can “back-space” and cut out the incorrect nucleotide.
What molecules does DNA polymerase adds to the 3’ end of the newly synthesized DNA chain?
dNTPs
What type of protein is DNA polymerase?
An enzyme
What does dNTP stand for?
Deoxynucleotide triphosphate
How many types of dNTPs are there and what are they called?
There are 4 dNTPs:
- dATP (deoxyadenosine triphosphate)
- dCTP (Deoxycytidine triphosphate)
- dTTP (deoxythymidine triphosphate)
- dGTP (deoxyguanosine triphosphate)
What do dNTPs bind with?
dNTPs base-pair with the nucleotide on the DNA template strand as follows:
dATP –> Thymine
dTTP –> Adenine
dCTP –> Guanine
dGTP –> Cytosine
When does DNA polymerase pause?
Each time after it adds a nucleotide.
Why does DNA polymerase pause after each nucleotide added?
To double-check if the correct nucleotide is added.
What does DNA polymerase do if the wrong nucleotide has been added?
DNA polymerase can “back-space” and cut out the incorrect nucleotide.
Does DNA polymerase have a process to prevent the wrong nucleotide from being added to a new strand of DNA?
Yes. DNA polymerase can “back-space” and cut out the incorrect nucleotide.
To which end does DNA polymerase add a nucleotide?
The 3’ end.
How are 3’ and 5’ pronounced?
Three prime and five prime
What does DNA ligase do?
This enzyme repairs small breaks in the phosphate-sugar backbone of DNA. It joints the Okazaki fragments on the lagging strand together.
What type of molecule is DNA ligase?
An enzyme
What enzyme repairs small breaks in the phosphate-sugar backbone of DNA?
DNA ligase
In DNA replication, what enzyme joins the Okazaki fragments on the lagging strand together?
DNA ligase
Define Primase and list its function.
Primase is an enzyme that makes a small RNA molecule that is known as a primer.
DNA polymerase can begin synthesizing DNA by adding dNTPs on the 3’ end of the primer.
What enzyme makes a small RNA molecule that is known as a primer?
Primase
DNA polymerase can begin synthesizing DNA by adding dNTPs on the 3’ end of what?
The primer, a small RNA molecule produced by primase.
How does DNA polymerase begin synthesizing DNA?
By adding dNTPs to the 3” end of the primer produced by primase.
On what end of the primer does DNA polymerase start adding dNTPs?
3’
What does helicase do?
Helicase unwinds the two strands of DNA at the replication fork.
Which enzyme unwinds the two strands of DNA at the replication fork?
Helicase
Where does helicase unwind DNA?
At the replication fork
What is topoisomerase?
The enzyme that releases the tension in the parental DNA molecule caused by unwinding at the replication fork.
What occurs as a result of helicase unwinding the DNA?
The unwinding creates tension in the DNA to come back together.
What is the enzyme that relieves the tension created by helicase?
Topoisomerase
Which strand is the leading strand in DNA synthesis?
The strand that is synthesized continuously.
The 3’ end of the newly-synthesized DNA molecule faces toward the direction the replication fork is opening up in.
Which strand of DNA is synthesized continuously?
The leading strand
What replication characteristic does the leading strand have that the lagging strand does not?
It is replicated continuously.
Also, it replicated at the 3’ end in the direction that the replication fork is opening up to.
What is the lagging strand in DNA synthesis?
The lagging strand is synthesized in short segments called Okazaki fragments.
The 3’ end of the newly-synthezied DNA molecule faces away from the direction that the replication for is opening up to.
What strand of DNA is synthesized in short segments in DNA replication?
The lagging strand
At which end of the DNA molecule does the lagging strand start DNA replication?
The 3’ end
Which strands, the leading or lagging strand starts DNA synthesis at the 3’ end?
Both strands
Which strand in DNA replication moves in a direction away from the direction that the replication fork is moving?
The lagging strand
What are the short segments of DNA synthesized in the lagging strand called?
Okazaki fragments
What are Okazaki fragments?
Short strands of newly synthesized DNA on the lagging strand
What is the origin of replication?
This is a sequence of DNA nucleotides where DNA replication begins.
What is the sequence of nucleotides where DNA replication begins called?
The origin of replication
What is transcription?
Transcription is the process of using the informatoin in a DNA sequence to make an RNA sequence.
What is the process of using the information in a DNA sequence to make an RNA sequence?
Transcription
What does RNA polymerase do?
RNA polymerase is the enzyme that joins NTPs together to form an RNA chain, based on the sequence of a template DNA.
What enzyme joins NTPs together to form an RNA chain, based on the sequence of a template DNA?
RNA polymerase
What is template DNA?
Template DNA is the strand of DNA to which NTPs bind to make the RNA molecule.
The binding of NTPs to the template DNA strand determine the sequence of bases in the RNA molecule.
The binding of NTPs to the template DNA strand determine what in the RNA molecule?
The sequence of bases in the RNA molecule
What is the strand of DNA that NTPs bind to to make RNA?
The template DNA
Match the name to the function of each:
dNTPs NTPs
DNA synthesis RNA synthesis
dNTPs are used in DNA synthesis
NTPs are used in RNA synthesis
What does NTP stand for?
Nucleotide triphosphates (specifically ribonucleotide triphosphate)
What is the abbreviation for ribonucleotide triphosphate and what function do they serve?
NTP. Used in RNA synthesis.
What is the abbreviation of deoxyribonucleotide triphosphate and where does it have a function?
dNTP. Functions in DNA replication.
What do NTPs and dNTPs have in common?
They both act as the building blocks and fuel, the first for RNA synthesis, the second for DNA replication.
What do NTPs do?
NTPs act as the building blocks and the fuel for RNA synthesis.
How do NTPs provide fuel for RNA synthesis?
The removal of two phosphate groups when the NTP is added to the growing RNA chain provides the energy for the reaction.
What is provided when two phosphate groups are removed from the NTP during a growing RNA chain?
Fuel (energy) for the reaction is provided
How many NTPs are there and what are they?
Four NTPs.
There is one for each of the nitrogenous bases found in RNA: ATP, CTP, GTP, UTP.
What are ATP, CTP, GTP and UTP?
NTPs used in RNA synthesis
What is messenger RNA?
mRNA contains a series of codons that correspond to a sequence of amino acids in the protein being made.
It acts as the template in translation.
What does mRNA contain that corresponds to a sequence of amino acids in the protein being made?
Codons
What acts as the template in translation?
mRNA
What does mRNA code for?
Proteins
What is tRNA?
rRNA is the RNA component of the ribosome.
What does rRNA do?
rRNA takes the role of the enzyme in translation, catalyzing the transfer of amino acids from a tRNA to the growing protein chain.
What molecule catalyzes the transfer of amino acids from a tRNA to the growing protein chain?
Ribosomal RNA
What does tRNA do?
Transfer RNA acts as an adaptor between the mRNA and the protein sequence being made.
What is the structure of tRNA?
Each tRNA has an anticodon at one end and a specific amino acid attached to the other end, forming an aminoacyl-tRNA. The anticodon binds to the codon in mRNA and the specific amino acid for which that codon codes is attached to the other end of the tRNA. There is a tRNA for each of the codons in the genetic code chart.
What is attached to each end of a tRNA molecule?
tRNA has an anticodon at one end and a specific amino acid attached to the other end.
This formation is an aminoacyl-tRNA.
Why is a tRNA called an aminoacyl-tRNA?
Because the structure is a tRNA with an amino group at one end and an anticodon at the other.
T/F
There is a tRNA for each of the codons in the genetic code chart.
True
What acts as an adapter between the mRNA and the protein sequence being made?
tRNA
What binds to the codon in mRNA?
The anticodon in tRNA
What do an anticodon and the specific amino acid coded for by mRNA represent?
The two ends of the tRNA molecule
What is translation?
Translation is the process of using the information in an mRNA template to make a protein (sequence of amino acids)
What is the process of using the information in an mRNA template to make a protein (sequence of amino acids)?
Translation
What does mRNA act as in translation?
The template
T/F
The sequence of codons in an mRNA molecule determines the sequence of amino acids in the protein that is made.
True
What determines the sequence of amino acids in the protein that is made?
The sequence of codons in an mRNA
What does the sequence of codons in an mRNA molecule determine?
The sequence of codons in an mRNA molecule determines the amino acids in the protein that is made.
What do aminoacyl-tRNAs do?
They act as monomers that join together to make the protein.
What act as monomers that join together to make a protein?
Aminoacyl-tRNAs
T/F
tRNA does not act as an adaptor molecule.
False
What does it mean that tRNA acts as an adaptor molecule?
It means that tRNA has an anticodon that binds to a a codon on the mRNA sequence which serves to match an amino acid to the codon.
What has an anticodon that binds to the codon on mRNA which serves to match an amino acid to the codon?
tRNA
What occurs when the anticodon of tRNA binds to mRNA?
The amino acid is transferred from the tRNA to the end of the protein chain that is being synthesized.
When is an amino acid transferred from the tRNA to the end of the protein chain that is being synthesized?
After the anticodon of the tRNA binds to the codon on mRNA.
What is a ribosome?
A large RNA-protein complex that acts as the enzyme in translation.
What complex acts as the enzyme in translation?
The ribosome
What catalyzes the chemical reaction that transfers the amino acid that is attached to a tRNA to the end of the protein chain being synthesized?
The ribosome
Where is the bond that links the amino acid to the tRNA broken?
At the ribosome
What results in breaking the bond that links the amino acids to the tRNA?
The ribosome catalyzes the chemical reaction that transfers the amino acid that is attached to a tRNA to the end of the protein chain that is being synthesized.
When a ribosome catalyzes the reaction that transfers the amino acid that is attached to the tRNA to the protein chain, when bonds are broken and which are created?
The bonds linking the amino acid to the tRNA are broken and a peptide bond is formed between amino acids and the protein chain.
When are the bonds linking the amino acid to the tRNA broken and a peptide bond formed between amino acids and the protein chain?
After the ribosome catalyzes the chemical reaction that transfers the amino acid attached to the tRNA to the end of the protein chain that is being synthesized.
What type of bonds are formed between the amino acids being added to the protein chain in translation?
Peptide bonds
Using the chart, fill in the nucleotide sequence of the anticodon and codon for Trp-tRNA
(the amino acid tryptophan attached to a tRNA bound to an mRNA).
Using the genetic code chart, we find that the codon that corresponds to the amino acid TRP is UGG. This will be the codon that is found in the mRNA sequence. The anticodon that is found on the tRNA will be the RNA sequence that binds to UGG, which is ACC. Each codon on the chart would have an aminoacryl-tRNA that has an anticodon that binds to the codon.
e.g. 6 codons code for leucine (Leu):
UUA, UUG, CUU, CUC, CUA and CUG.
6 different aminoacyl-tRNAs with Leu attached, the anticodons that bind to those codons:
AAU, AAC, GAA, GAG, GAU and GAC.)
Describe the summary of events at the DNA replication fork.
- Helicase enzymes unwind the parental double helix.
- Topoisomerase proteins stabilize the unwound parental DNA.
- The leading strand is synthesized continuously from the primer by DNA polymerase.
- The lagging strand is synthesized discontinuously. Primase, an RNA polymerase, synthesizes a short RNA primer, which is then extended by DNA polymerase.
- DNA polymerase digests RNA primer and replaces it with DNA.
- DNA ligase joins the discontinuous fragments (Okazaki fragments) of the lagging strand.
Describe the summary of events in DNA replication.
- Helicase enzymes unwind the parental double helix.
- Topoisomerase proteins stabilize the unwound parental DNA.
- The leading strand is synthesized continuously from the primer by DNA polymerase.
- The lagging strand is synthesized discontinuously. Primase, an RNA polymerase, synthesizes a short RNA primer, which is then extended by DNA polymerase.
- DNA polymerase digests RNA primer and replaces it with DNA.
- DNA ligase joins the discontinuous fragments (Okazaki fragments) of the lagging strand.
What is the result from DNA replication?
Each DNA molecule has one of the parent strands and one newly-made strand.
This is called semiconservative DNA replication.
What is semiconservative DNA replication?
Semiconservative DNA replication means that one of the strands is a parent strand and one is a newly-formed strand in each of the 2 resulting DNA molecules.
Mark the replication fork and the origin of replication.
Check email response from Dr. Suran
What type of replication is DNA replication?
Bidirectional, semi-conservative
What is a missense mutation?
Missense mutations are one of the three types of base substitutions (along with silent: no change in base sequence and nonsense mutations: inserts stop codon in protein sequence) whereby a single-base substitution results in a change in a single amino acid in the entire sequence of the protein.
In a missense mutation, a codon that codes for an amino acid is changed to a codon that codes for a different amino acid.
What type of mutation is a base substitution mutation whereby a single-base substitution results in a change in a single amino acid in the entire sequence of the protein.
Missense mutation
In what type of mutation does a codon that codes for an amino acid get changed to a codon that codes for a different amino acid.
Missense mutation
What is a silent mutation?
A silent mutation is one of the three types of base substitutions whereby a single base is replaced with another but the corresponding codon change corresponds to the same amino acid.
A codon is changed to a different codon that corresponds to the same amino acid.
What type of mutation is one of the three types of base substitutions whereby a single base is replaced with another but the corresponding codon change corresponds to the same amino acid.
Silent mutation
The mutation where a codon is changed to a different codon that corresponds to the same amino acid.
Silent mutation
What type of base substitution changes the sequence in a codon but not the resulting amino acid?
Silent mutation
What type of mutation is a nonsense mutation?
A nonsense mutation is a type of base substitution whereby a stop codon is inserted in a protein chain that stops the addition of amino acids.
No amino acids are added after this codon.
What mutation is a type of base substitution whereby a stop codon is inserted in a protein chain that stops the addition of amino acids.
Nonsense mutation
What mutation results in no amino acids being added after the addition of this codon?
Nonsense mutation
What are the three types of base substitution mutations?
- Missense mutation: a change in the codon that results in the coding of a different amino acid.
- Nonsense mutation: the insertion of a stop code in the sequence that results in no more amino acids added to the chain.
- Silent mutation: a change in the codon that codes for the same amino acid in the chain.
What are the following: Missense mutation, nonsense mutation and silent mutation?
The three types of base substitution mutations
Which mutation makes a change in the codon that results in the coding of a different amino acid?
Missense mutation
What type of mutation inserts a stop code in the sequence that results in no more amino acids added to the chain?
Nonsense mutation
What type of mutation makes a change in the codon that codes for a different amino acid in the chain.
Missense mutation
What type of mutation makes a change in the codon that codes for the same amino acid in the chain.
Silent mutation
What is a frame-shift mutation?
A frameshift mutation is a mutation that does not happen in multiples of three.
This changes the reading frame (where one codon ends and the next begins) downstream of the mutation. This will most likely change all of the amino acids downstream of the mutation and will also likely change the length of the protein.
What is a nonframeshift mutation?
A mutation that occurs in a multiple of three.
Results in an additional amino acid being added to the sequence.
What is the difference between a frameshift mutation and a non-frameshift mutation?
A frameshift mutation does not occur in multiplies of three bases (no one codon) and a non-frameshift mutation occurs in multiples of three (an additional codon).
Which mutation does not occur in multiplies of three bases and which mutation does?
A frameshift mutation does not occur in multiples of three and a non-frameshift mutation occurs in multiples of three.
Which type of mutation occurs in multiples of three and what is the result?
A non-frameshift mutation occurs in multiples of three and results in an additional amino acid added to a sequence.
Which type of mutation does not occur in multiples of three and what is the result?
A frameshift mutation does not occur in multiples of three and the additional base(s) added will shift the sequence to change all the subsequent amino acids in the protein.
What type of mutation will change all the amino acids in the sequence after the point of the mutation?
Frameshift mutation
What type of mutation inserts another amino acid in the protein sequence?
Non-frameshift mutation
What type of mutation is the following and how would it affect the protein sequence if it occured at the 50th codon of a 100 codon chain?
A mutation that changes the codon UCA to UCC
This is a silent mutation because both UCA and UCC code for Serine. If this occured at the 50th codon in a protein made from 100 codons, the new protein would be identical to the original protein.
If a mutation caused both the original codon and the new codon to code for the same protein and the change meant that the new protein sequnence would be identical to the original, what type of mutation would this be?
Silent mutation
What type of mutation is the following and how would it affect the protein sequence if it occured at the 50th codon of a 100 codon chain?
A mutation that changes the codon UCA to UUA
UCA corresponds to Ser and UUA corresponds to Leu so this is a missense mutation.
If this mutation occured at the 50th codon in a protein made from a 100-codon mRNA, the protein made from the mutant mRNA would be identical to one made from the orginal mRNA except for the 50th amino acid which would be Leu instead of Ser.
If a mutation occured at the 50th codon in 100-codon mRNA and the protein made from the mutant mRNA was identical to one made from the orginal except the 50th amino acid was changed from UCA instead of UUA, what type of mutation would this be?
Missense mutation
What type of mutation is the following and how would it affect the protein sequence if it occured at the 50th codon of a 100 codon chain?
A mutation that changes the codon UCA to UAA
UCA corresponds to Ser, UAA is a stop codon. This is a nonsense mutation. If this mutation occurred at the 50th codon in a protein that was made from a 100-codon mRNA, the protein made from the mutant mRNA would be identical to one made from the original mRNA for the first 49 amino acids. At this point the mutant protein would end.
What type of mutation would occurr at the 50th codon in a protein that was made from a 100-codon mRNA, where the protein made from the mutant mRNA would be identical to one made from the original for the first 49 amino acids but at this point the mutant protein would end?
Nonsense mutation because the mutant inserts a stop codon.
What kind of damage is caused by exposure to UV light?
UV light is a mutagen that can cause thymine dimers to form in DNA. In thymine dimers, two neighboring thymine amino acids in the DNA chain chemically react and become covalently bonded to each other. As a result, they cannot pair normally with the opposite strand. The cell can no longer use the top strand for DNA replication or transcription.
How is the damage caused by UV light repaired?
This damage is repaired through excision repair:
- Proteins recognize the deformation of the DNA backbone caused by the thymine dimer.
- An endonuclease cuts out the dimer and some of the surrounding DNA
- The DNA is repaired by a DNA polymerase using the complementary strand as a template
- Ligase seals the nick between the newly-made DNA and the old stand of DNA.
What type of damage is being repaired in the following steps and what is this repair process called?
- Proteins recognize the deformation of the DNA backbone caused by the thymine dimer.
- An endonuclease cuts out the dimer and some of the surrounding DNA
- The DNA is repaired by a DNA polymerase using the complementary strand as a template
- Ligase seals the nick between the newly-made DNA and the old stand of DNA.
This repair process is repairing the damage done by UV light exposure to correct thymine dimers. This is called excision repair.
By what process is the damage caused by UV light exposure repaired?
Excision repair
What are specifically damaged by exposure to UV light?
Neighboring thymine bases
Put the following steps in order for the excision repair process:
- Ligase seals the nick between the newly-made DNA and the old stand of DNA.
- An endonuclease cuts out the dimer and some of the surrounding DNA
- The DNA is repaired by a DNA polymerase using the complementary strand as a template
- Proteins recognize the deformation of the DNA backbone caused by the thymine dimer.
4, 2, 3, 1. The list should be:
- Proteins recognize the deformation of the DNA backbone caused by the thymine dimer.
- An endonuclease cuts out the dimer and some of the surrounding DNA
- The DNA is repaired by a DNA polymerase using the complementary strand as a template
- Ligase seals the nick between the newly-made DNA and the old stand of DNA.
What is the enzyme that excises the dimer caused by a mutagen like UV light?
Endonuclease
What does endonuclease do?
Endonuclease is an enzyme that excises the thymine dimer (and some surrounding DNA) caused by overexposure to UV light.
What enzyme excises the thymine dimer (and some surrounding DNA) caused by overexposure to UV light?
Endonuclease
What enzyme seals the nick between the newly-made DNA and the old strand of DNA after the excision of a thymine dimer and subsequent replacement?
Ligase
What are the enzymes involved in repair after overexposure to UV light?
- Endonuclease (excises the damaged thymine dimers and a bit of surrounding DNA)
- DNA polymerase (repairs the DNA using the complementary strand as a template)
- Ligase (seals the nick bewteen the newl-made DNA and the old strand of DNA)
What process are endonuclease, DNA polymerase and ligase involved in together?
Excision and repair of thymine dimers in skin overexposed to UV light.
What is the Ames test and descibe the procedure used.
The Ames test uses a strain of Salmonella that has a pre-existing mutation that prevents them from synthesizing histidine. These Salmonella require media supplemented with histidine in order to grow, as this amino acid is necessary for making proteins.
To perform the test, a culture of this Salmonella is split in two:
- To one half of the culture, the potential mutagen and rat liver extract is added.
- To the other half of the culture, only the rat liver extract is added.
Both cultures are then plated on histidine-lacking media.
Describe the results that would be seen in the Ames test for both a mutagenic substance and a non-mutagenic substance.
If the substance is mutagenic:
- It will cause mutations in the Salmonella. Some of these mutations will allow the Salmonella to make histidine again. Therefore, there will be more colonies on the experimental plate than on the control plate.
If the substance is not mutagenic:
- It will not cause mutations in the Salmonella. Therefore, there will be the same amount of colonies on the experimental plate as there is on the control plate. Both cultures of Salmonella will experience spontaneous mutations (not caused by the mutagen), so we expect to see colonies on both plates.
This result of the Ames test is an indication of mutagenic or non-mutagenic substance?
It will cause mutations in the Salmonella. Some of these mutations will allow the Salmonella to make histidine again. Therefore, there will be more colonies on the experimental plate than on the control plate.
Mutagenic
Is this result from the Ames test mutagenic or non-mutagenic?
It will not cause mutations in the Salmonella. Therefore, there will be the same amount of colonies on the experimental plate as there is on the control plate. Both cultures of Salmonella will experience spontaneous mutations (not caused by the mutagen), so we expect to see colonies on both plates.
Non-mutagenic
Is this result from the Ames test mutagenic or non-mutagenic?
There will be the same amount of colonies on the experimental plate as there is on the control plate.
Non-mutagenic
Is this result from the Ames test mutagenic or non-mutagenic?
There will be more colonies on the experimental plate than on the control plate.
Mutagenic
Is this result from the Ames test mutagenic or non-mutagenic?
Some of these mutations will allow the Salmonella to make histidine again.
Mutagenic
Is this result from the Ames test mutagenic or non-mutagenic?
We expect to see colonies on both plates.
Non-mutagenic
Briefly describe the difference between regulation by repression and regulation by induction.
There are two types of regulatory proteins: those that add a molecule that turns the gene on are called induction and those that add a molecule to turn the gene off are called repression.
In induction, expression of the gene will turn on in response to a stimulus (usually a specific molecule). Enzymes involved in catabolic pathways are often inducible, which the presence of the molecule to be broken down in the pathway is the stimulus to start gene expression.
In repression, expression of the gene will turn off in response to a stimulus (usually a specific molecule). Enzymes involved in anabolic pathways are often repressible, meaning that the absence of the molecule that the pathway synthesizes is the stimulus to start gene expression.
What are two types of regulatory proteins?
Induction and repression
What does induction mean in the order of regulation by expression?
The presense of a certain molecule or molecules (stimulus) turns gene expression on.
The presense of a certain molecule or molecules (stimulus) that turns gene expression on is called what?
Induction