MCAT Biochemistry Flashcards
1
Q
What is the central dogma of molecular biology?
A
DNA —-> RNA —-> Protein
2
Q
How can DNA be copied?
A
Through the process of replication.
3
Q
By what process is DNA converted into RNA?
A
Transcription
4
Q
By what process is RNA converted into protein?
A
Translation
5
Q
By what process is RNA converted into DNA?
A
Reverse Transcription
6
Q
Reverse Transcriptase
A
generates complementary DNA or cDNA from an RNA template.
7
Q
Why are reverse transcriptases needed?
A
Needed for the replication of retroviruses such as HIV.
8
Q
Why are RNA viruses important?
A
They can directly be translated into proteins, can serve as the template for another RNA molecule.
Ex: SARS, Influenza, Measles
9
Q
Non-coding RNA
A
directly perform functions in the cell, are not translated into proteins. Ex: tRNA and rRNA.
10
Q
Epigenetics
A
study of heritable changes in gene activity that are not caused by changes in DNA sequence.
Ex: DNA methylation and histone modifications.
11
Q
How are peptide bonds formed?
A
The amino group of one amino acid carries out a nucleophilic attack on the carboxyl group of another amino acid forming an amide bond and releasing a water molecule.
12
Q
What is unique about the peptide bond?
A
It is planar and rigid, due to the partial double bond character by resonance stabilization.
13
Q
What are the two ways in which peptide bonds can be broken?
A
acid hydrolysis and proteolysis
14
Q
Breaking peptide bonds, by acid-hydrolysis + heat specific or non-specific?
A
non-specific cleavage.
15
Q
Breaking peptide bonds, by proteolysis specific or non-specific?
A
specific cleavage.
16
Q
Proteolysis
A
will cleave peptide bonds between certain specific amino acids.
17
Q
Trypsin
A
a protease that cleaves on carboxyl side of lysine and arginine.
18
Q
What is special about histidine?
A
Histidine’s side chain has a pKa that is close to the physiological pH. Therefore, histidine will exist in both protonated and deprotonated forms and will be useful to have in an enzyme’s active site.
19
Q
pH < pKa
A
protonated
20
Q
pH > pKa
A
deprotonated
21
Q
What is special about proline?
A
proline has a secondary alpha amino group.
22
Q
What is special about glycine?
A
glycine not chiral, glycine is considered to be very flexible.
23
Q
What role to proline and glycine play in secondary structure of proteins?
A
proline and glycine play a role in disrupting alpha helices by introducing kinks.
24
Q
What is special about cysteine?
A
The thiol (SH) group of cysteine can form disulfide bonds.
25
Where are disulfide bonds favored?
extracellular space, because it is an oxidizing environment.
26
Where are disulfide bonds not favored?
intracellular environment, reducing environment will favor thiols.
27
Where is hemoglobin found?
Hemoglobin is found in red blood cells.
28
What is the function of hemoglobin?
responsible for picking up oxygen, and transports oxygen to various tissues in our body where it helps in the production of ATP that is used as energy.
29
__________ are the building block of hemoglobin proteins.
Amino acids
30
__________ are the building block of hemoglobin proteins.
Amino acids
31
chiral carbon
has 4 unique groups bound to it.
32
_______ refers to optical activity.
Chirality
33
Which amino acid is not chiral?
glycine
34
________ form of an amino acid is the only form you will find in the human body.
L-form
35
Isoelectric point (pI)
the pH at which an amino acid is electrically neutral.
36
Enantiomers
non-superimposable mirror images.
37
What is the average pKa of an amino group?
9
38
What is the average pKa of an amino group?
9
39
What is the average pKa of a carboxyl group?
2
40
Which amino acids are non-polar and have alkyl side chains?
1. glycine
2. alanine
3. methionine
4. leucine
5. valine
6. isoleucine
7. proline
41
Which amino acids are non-polar and have aromatic side chains?
1. phenylalanine
2. tryptophan
42
Which amino acids are polar and have neutral side chains?
serine, threonine, asparagine, glutamine, cysteine, tyrosine.
43
Which amino acids are polar and have acidic side chains?
aspartic acid and glutamic acid.
44
Which amino acids are polar and have basic side chains?
histidine, lysine, arginine.
45
Amyloid
clumps of misfolded proteins.
46
Primary structure
the linear sequence of amino acids, consists of peptide bonds.
47
Secondary structure
linear sequence of amino acids folds upon itself, consists of backbone interactions and hydrogen bonding.
48
What are the two motifs of secondary structure?
alpha helix and beta sheet
49
What is a parallel beta sheet?
The N and C termini of one polypeptide lines up with the N and C termini of another polypeptide.
50
What is an anti-parallel beta sheet?
The N and C termini of one polypeptide does not line up with the N and C termini of another polypeptide.
51
Tertiary structure
higher order folding within a polypeptide chain. Consists of distant interactions, hydrogen bonding, van der Waals, disulfide bridge formation, and hydrophobic interactions.
52
Quaternary structure
describes the bonding between multiple polypeptides.
53
Denatured proteins
proteins that have become unfolded or inactive.
54
Solvation shell
layer of solvent that is surrounding a protein.
55
What are some ways proteins can be denatured?
temperature, pH, chemicals, enzymes.
56
How can temperature denature proteins?
increase temperature, destroys secondary, tertiary, and quaternary structure of protein.
57
How can pH denature proteins?
disruption of ionic bonds, tertiary and quaternary structure disrupted.
58
How can chemical denature proteins?
disrupts hydrogen bonding, secondary, tertiary, and quaternary structures.
59
How can enzymes denature proteins?
disrupting primary structure of proteins.
60
Acid-Base catalysts
happens when enzymes act like either acids or bases.
61
Covalent catalysis
enzymes form a covalent bond with another molecule usually their target molecule.
62
Electrostatic catalysis
stabilizing charges
63
Transition state of a reaction
highest energy point on the path from reactant to product.
64
Activation Energy or free energy of activation
the difference between the energy level where we start and the top of our transition state.
65
Standard free energy change
represents the net change in energy levels.
66
How do enzyme speed up a reaction?
by lowering the reaction's activation energy.
67
Are enzymes consumed in a reaction?
No
68
Induced fit model of enzyme catalysis
enzyme and substrate have changed their shape so that the enzyme and substrate can bind really tightly.
69
Active site
location on the substrate where the enzyme binds.
70
_________ takes place at the active site of an enzyme. ____________ take place at the allosteric site of an enzyme.
Reactions; regulation
71
Kinase
adds phosphate functional groups to different substrates.
72
Transferase
move some functional group "X" from one molecule to another molecule. Ex: peptidyl transferase.
73
Ligase
catalyzes reactions between two molecules that are combining to form a complex between the two. Ex: DNA ligase
74
Oxidoreductase
catalyze oxidation-reduction reactions.
75
Dehydrogenase
removal of a hydride functional group
76
Isomerase
molecule is being converted to one of its isomers.
77
Hydrolase
uses water to cleave a molecule.
78
Lyase
catalyze the dissociation of a molecule without using water and oxidoreductase.
79
Coenzymes
are organic carrier molecules.
Ex: NADH, coA
80
Cofactors
participate in catalysis
Ex: Mg2+ in DNA Polymerase
81
Vitamin B3 generates the precursor for which cofactor
niacin ---> NAD
82
Vitamin B5 generates the precursor for which cofactor
coA
83
Minerals
inorganic cofactors
Ex: Mg2+, Ca2+
84
alpha-amylase
break down complex carbohydrates into small simple carbohydrates.
85
pepsin
breaks down big proteins into smaller peptides.
86
Vmax
maximum speed of a reaction.
87
The Steady State Assumption
concentration of ES (enzyme-substrate complex) is constant.
Formation of ES = Loss of ES.
88
Michaelis-Menten Equation
V0 = Vmax [S]/ [S] + Km
89
Km
Michaelis constant, Km is the [S] where V0 = 1/2 Vmax.
90
What is kcat?
turnover number; how many substrates an enzyme can turn into product in one second at its maximum speed.
91
Catalytic efficiency
kcat/Km, how good an enzyme is at speeding up reactions.
92
How can we increase the catalytic efficiency of an enzyme?
increase kcat and decrease Km.
93
Cooperativity
susbtrate binding changing substrate affinity.
94
Positive Cooperative Binding
substrate binding increases the affinity for subsequent substrate; sigmoidal shaped curve.
95
Negative Cooperative Binding
substrate binding decreases the affinity for subsequent substrate.
96
Non-cooperative binding
substrate binding does not affect affinity for subsequent substrate.
97
What type of cooperativity does hemoglobin exhibit?
positive.
98
Myoglobin
oxygen carrying molecule that is found in muscle cells.
99
What type of cooperativity does myoglobin exhibit?
non-cooperative; hyperbolic shaped curve.
100
Allosteric activator
increases enzymatic activity and activates them.
101
Allosteric inhibitor
decreases enzymatic activity and inhibits the enzymes.
102
Feedback Loop
downstream products regulate upstream reactions.
103
Homotropic
substrate and the regulator are the same molecules.
104
Heterotropic
substrate and the regulator are different molecules.
105
What are examples of non-enzymatic proteins?
receptors/ion channels, transport proteins, motor proteins, and antibodies.
106
Receptor
proteins that receive or bind a signaling molecule.
107
Transport proteins
responsible for binding small molecules and transporting them.
108
Motor proteins
crucial for cellular motility.
109
Myosin
protein responsible for generating the forces exerted by contracting muscles.
110
Kinesin and dynein
responsible for intracellular transport.
111
Antibodies
components of the adaptive immune system whose main function is to find foreign antigens and target them for destruction.
112
Covalent modifications to proteins
involve forming or breaking a bond.
113
Post-translational modifications to proteins involve:
methylation, acetylation, glycosylation
114
Zymogen
are inactive enzymes that require covalent modification in order to become active.
115
Suicide Inhibitors
covalently bind the enzyme and prevent it from catalyzing reactions, permanently bind their target.
116
Where is DNA found in eukaryotes?
Nucleus
117
What is the structure of DNA strands?
antiparallel
118
Telomeres
they protect the ends of chromosomes from deterioration and prevent chromosomes from sticking to each other.
Highly repetitive DNA.
119
What happens to telomeres each time chromosomes replicate?
Telomeres get shorter.
120
What is the function of telomerase?
lengthen telomeres, and bring them back to original length.
121
What is single copy DNA?
DNA sequence that does not repeat itself.
122
Most important genes are ____________.
single copy.
123
Where is repetitive DNA found?
near the centromeres.
124
What type of DNA is likely to have higher mutation rates?
Repetitive DNA
125
Where are centromeres located?
at the center of the chromatid.
126
DNA Polymerase
enzyme that is adding more and more nucleotides to grow DNA strand, can only add nucleotides on the 3' end.
127
What is the direction of DNA polymerase?
can only extend DNA in the 5' to 3' direction.
128
Topoisomerase
enzyme that helps us unwind the tightly wound helix.
129
Helicase
breaking the hydrogen bonds between our nitrogenous bases.
130
DNA primase
puts an RNA primer that is needed to initiate the process of DNA replication.
131
DNA ligase
puts strands together.
132
Transcription
DNA to messenger RNA (mRNA).
133
Where does transcription in eukaryotes occur?
in the nucleus.
134
Where does transcription in prokaryotes occur?
cytoplasm.
135
How does RNA polymerase know when to start?
attaches to a sequence known as a promoter to start, moves in the 5' to 3' direction.
136
Where does RNA polymerase stop?
stops at the terminator, several mechanisms, one is mRNA that is coded forms a hairpin which impair the polymerase to keep going.
137
How is mRNA processed in eukaryotes?
1. 5'-methylguanosine cap added.
2. poly-A tail
3. introns are spliced and removed, and exons are ligated.
138
What is the ribosome made of?
made of proteins and ribosomal RNA (rRNA)
139
Codon
every three nucleotides that code for an amino acid.
140
How many different codons are there?
64 codons
61 of the codons code for amino acids.
3 codons are stop codons.
141
tRNA (transfer RNA)
delivers amino acids to the ribosome.
142
How does tRNA bind to mRNA?
anticodon of tRNA binds to codon of mRNA.
143
What are the three sites on the ribosome?
A site, P site, E site
144
What is the A site?
aminoacyl site: is the place where the tRNA that is bound to one amino acid is going to bind on the ribosome.
145
What is the P site?
polypeptide chain is forming.
146
What is the E site?
exit site on the ribosome.
147
What is unique about prokaryotic transcription and translation?
transcription and translation happen at the same place and can happen at the same time.
148
What is the Shine-Dalgarno sequence?
is the site that the ribosome is going to recognize and bind to.
149
How does ribosome start the reaction in eukaryotes?
ribosome will recognize 5' cap and bind to it.
150
Where does transcription and translation take place in eukaryotes?
Transcription: nucleus
Translation: cytoplasm
151
What is the difference between the first amino acid in prokaryotes and eukaryotes?
first amino acid in prokaryotes: formyl-methionine
first amino acid in eukaryotes: methionine.
152
What is special about formyl-methionine?
f-Met acts as an alarm system in the human body to trigger an immune response.
153
Function of DNA Polymerase III
add nucleotides and sense a mistake during DNA replication. Has 3' to 5' exonuclease activity.
154
What is exonuclease activity?
removing a nucleotide from the end of a DNA strand.
155
What is endonuclease activity?
removes nucleotide from the middle of a DNA strand.
156
Function of DNA Polymerase I
also has exonuclease activity 5' to 3'. Will remove the RNA primer at the end of replication.
157
What are the steps of the mismatch repair mechanism?
1. proteins will recognize mismatch by the distortion of the sugar backbone of DNA.
2. exonuclease will remove incorrect nucleotide.
3. DNA polymerase will insert correct nucleotide.
4. DNA ligase will connect new nucleotide to its side and with complementary nucleotide.
158
How do we distinguish between parent strand and new strand of DNA in bacteria?
The parental strand will have adenines that are methylated.
159
What can two thymine based form?
pyrimidine dimer.
160
Mutation
change in the sequence of DNA.
161
DNA damage
damage to structure of DNA.
162
What are some examples of endogenous (internal) DNA damage?
reactive oxygen species, superoxide anion, peroxides.
163
What are some examples of exogenous (external) DNA damage?
UV rays, gamma rays, X-rays.
164
How do reactive oxygen species end up in cells?
reactive oxygen species are a normal byproduct of the electron transport chain.
165
Antioxidant
a molecule that helps protect us against the damaging effect of reactive oxygen species. Ex: Vitamin C and Vitamin E.
166
Explain the steps of nucleotide excision repair?
1. endonuclease is going to remove the pyrimidine dimers.
2. DNA polymerase will come and bring the nucleotides that belong there.
3. DNA ligase will make sure that the new nucleotides are attached to the correct side and the complementary nucleotide.
167
What are some of the fates of a cell with damaged DNA?
1. dormant state; ages and does not divide senescence.
2. apoptosis; programmed cell death.
3. cancer: unregulated cell division
168
What is melanoma and how does it occur?
Melanoma is a skin cancer that occurs when NER is not workin properly which leads to unregulated cell division.
169
Conservative replication
we have an old pair of DNA and a completely new pair of DNA.
170
Dispersive replication
two pairs of DNA, each one of those pairs we have some old DNA and new DNA dispersed within ds DNA.
171
Semiconservative replication
each pair has one old strand and one new strand.
172
Explain the significance of the Meselson-Stahl experiment.
experiment proved that DNA replication is semi-conservative.
173
What are two types of protein modifications?
co-translational modifications and post-translational modifications.
174
What are co-translational modifications?
changes that happen to the polypeptide while it is being translated. Ex: acetylation.
175
What is acetylation?
first amino acid, which is usually methionine is removed and in its place we put an acetyl group.
176
What are some examples of post-translational modifications?
glycosylation, lipidation, phosphorylation, ubiquitination, methylation of histones, and proteolysis.
177
Glycosylation
adding of a carbohydrate to a protein. Happens to proteins that end up being embedded in the cell membrane.
178
What is an application of glycosylation?
use them in A, B, O blood groups. Specific carbohydrates are attached to red blood cells that allow us to identify whether it is A, B, or AB. O blood type has no carbohydrate attached to it.
179
Lipidation
add lipid to a protein that will be attached to cell membrane.
180
What are GPI anchors?
are lipids that help to attach or tether proteins to the cell membrane.
181
Phosphorylation
adding of a phosphate group to a protein or to an enzyme. Ex: Na+/K+ ATPase
182
How does the sodium-potassium pump work?
there are three receptor sites for sodium and two receptor sites for potassium on the Na+/K+ ATPase.
When this enzyme is phosphorylated a conformational change causes the sodium to be released and the potassium to enter the cell.
Therefore, outside of the cell; there is a high concentration of Na+ and a low concentration of K+.
Inside the cell there is a low concentration of Na+ and high concentration of K+.
183
For every _______ Na+ that are pumped out _______ K+ are pumped in.
3 Na+
2 K+
184
Histones
proteins around which DNA wraps itself, helps to package DNA in a very tight and organized manner.
185
What is the role of methylation in histones?
methylating and demethylating histones helps to turn certain genes on and off.
186
Proteolysis
take a protein and cut it to activate it. Ex: zymogen
187
Ubiquitination
add a protein ubiquitin to mark the protein for degradation and breakdown.
188
Lac operon
contains genes that will help E.coli to break down lactose.
189
Function of lac Z gene
codes for protein beta galactosidase
190
Function of beta-galactosidase
break down lactose into glucose and galactose.
191
Function of lac Y gene
codes for lactose permease.
192
Function of lactose permease
brings lactose into the cell.
193
Function of lac A gene
codes for an enzyme that helps in lactose metabolism.
194
Describe the regulation of transcription by the lac operon
E.coli uses glucose as its preferred fuel source.
Default lac z, y, and a not expressed due to repressor that blocks RNA polymerase from transcribing the genes.
Lots of lactose: lactose will attach to repressor causing a conformational change that will cause repressor to come off operator site and allow for transcription.
Lactose low: lactose comes off repressor and repressor goes back to operator site. Only transcribes those genes that we need.
195
At what point during normal DNA replication is genetic material lost from the template?
joining of Okazaki fragments.
196
What subunits are the human ribosome made of?
60 S and 40 S subunits.
197
What subunits are the prokaryotic ribosomes made of?
50 S and 30 S subunits.
198
Constitutive expression
transcribed at base line.
199
What are the key takeaways from the lac operon model?
1. Interaction between the inducer and the repressor molecules that mediate gene expression.
2. Cells expend energy to make enzymes only when necessary.
200
How is DNA packed into chromosomes?
DNA is packed into chromosomes in the form of chromatin, also known as supercoiled DNA.
201
What is chromatin made of?
DNA, histone proteins, and non-histone proteins.
202
What are nucleosomes?
repeating units in chromatin.
203
What are nucleosomes made of?
made of 146 base pairs of double helical DNA that is wrapped around a core of 8 histones. H2A, H2B, H3, and H4.
204
Where does acetylation occur in histones?
at the amino terminal tails of these histone proteins.
205
Which enzyme carries out acetylation of histones?
histone acetyltransferase (HATs)
206
What is the function of histone deacetylase (HDAC)?
removes acetyl groups.
207
What is the importance of the acetylation of histones?
leads to uncoiling of this chromatin structure, and allows it to be accessed by transcription machinery for the expression of genes.
208
What is the importance of histone deacetylation?
leads to a condensed, or closed structure of chromatin, and less transcription of these genes.
209
Heterochromatin
densely packed, and transcriptionally active DNA.
210
Euchromatin
less dense transcriptionally active DNA.
211
Carcinogenesis
development of cancer.
212
Operator
sequence of DNA to which a transcription factor protein combined.
213
Promoter
is the sequence of DNA to which the RNA polymerase binds to start transcription.
214
General Transcription factors
class of proteins that bind to specific sites on DNA to activate transcription.
215
Activators
increase the attraction of RNA polymerase for the promoter.
216
Catabolite activator protein
activates transcription of the lac operon of E.coli.
217
What is the mechanism of the catabolite activator protein?
cAMP is produced during glucose starvation.
cAMP binds to CAP which causes a conformational change that allows CAP protein to bind to a DNA site.
CAP recruits RNA polymerase to promoter.
218
Enhancers
sites on the DNA that are bound by activators in order to loop the DNA.
219
Repressors
are proteins that bind to the operator impeding RNA polymerase progress on the strand and thus impeding the expression of the gene.
220
Inducer
molecule that initiates transcription.
221
RNA editing
a process that results in sequence variation in the RNA molecule and is catalyzed by various enzymes.
Methods: insertion, deletion, substitution.
222
What is the function of adenosine deaminase on RNA?
convert specific adenosine residues to inosine in an mRNA molecule by hydrolytic deamination.
223
What is the function of cytosine deaminase acting on RNA?
deamination of cytosine to uridine by uridine deaminase.
224
Non-coding RNA
is a functional RNA molecule that actually skips the last step (RNA to protein) and is not translated into a protein.
225
Oncogene
are genes that code for proteins that normally direct cell growth.
226
Mitogen
chemical substance that encourages a cell to start cell division, triggers mitosis.
227
What are the mechanisms by which proto-oncogene is converted to oncogene?
1. deletion/point mutation
2. gene amplification
3. chromosomal rearrangement.
228
Chromosomal rearrangement
over expressed proteins or fusion protein.
229
Sarcoma
tumor of mesenchymal cells, or connective tissue.
230
Ras oncogene
which codes for a small GTPase which hydrolyzes GTP into GDP and phosphate.
231
Tumor supressor genes
are those genes whose protein products either have a halting effect on the regulation of the cell cycle, or they can also promote apoptosis.
232
Two hit hypothesis
both alleles must be present in order to lead to the cancerous phenotype.
233
Retinoblastoma
rapidly developing cancer that originates from the immature cells of the retina.
234
What is p53?
very critical tumor suppressor protein.
235
Cyclin-dependent kinase complex (CDKs)
the complex responsible for pushing the cell from G1 to S phase in the cell cycle.
236
How does micro RNA primarily aid in transcriptional regulation?
gene silencing through translational repression or target degradation.
237
The difference between normal hemoglobin and HbS is that one ___________ amino acid residue is being replaced with a __________ amino acid residue.
glutamate, valine
238
Mutations originate at the _______ level, but show their effects at the _________ level.
DNA, protein
239
What are the different types of mutations that have effects on the DNA?
point mutation and frameshift mutation
240
What causes point mutations?
caused by base substitution.
241
What are the different types of base substitution?
transition, transversion, and mismatch.
242
What is a transition?
swap between two purines or two pyrimidines.
243
What is a transversion?
swap between purine and pyrimidine.
244
What is a mismatch?
non-Watson-Crick base pairing.
245
What causes frameshift mutations?
insertion and deletion.
246
What are insertions?
when an extra DNA base is added.
247
What are deletions?
when a DNA base is deleted.
248
What are some large scale mutations that can exist at the chromosomal level?
Translocation and inversion
249
What is a translocation?
gene from one chromosome is swapped for another gene on a different chromosome. Occurs between non-homologous chromosomes.
250
What is a inversion?
two genes on the same chromosome switch places.
251
Mutagen
any chemical substance or physical event that can cause genetic mutations.
252
What are two different types of mutagens?
endogenous and exogenous
253
What is an endogenous mutagen?
mutagen that is already found in the organism. Ex: reactive oxygen species
254
What can reactive oxygen species do?
double strand breaks in DNA and base modification.
255
What is an exogenous mutagen?
comes from outside the affected organism.
Ex: intercalators and base analogoues.
256
What can intercalators do?
deform the structure of DNA.
257
What can base analogoues do?
pretend to be some base but act differently.
258
What are carcinogens?
substance that can lead to cancer.
259
Are all carcinogens mutagens?
No
260
Allele
one small section on a chromosome that codes for a specific gene.
261
Homozygous
same allele from both parents.
262
Complete dominance
only 1 allele in the genotype is seen in the phenotype.
263
Codominance
both alleles in the genotype is seen in the phenotype.
264
Incomplete dominance
a mixture of the alleles in the genotype is seen in the phenotype.
265
What are the assumptions made in the Hardy-Weinberg Principle in order to have stable allele frequencies?
1. no selection
2. no mutation
3. large population
4. p + q = 1
266
What is Hardy-Weinberg Principle equation?
p^2 + 2pq + q^2 =1
267
What is the "p" in hardy-weinberg?
frequency of dominant allele.
268
What is the "q" in hardy-weinberg?
frequency of recessive allele.
269
What is the "p^2" in hardy-weinberg?
probability for someone in the population to be homozygous dominant.
270
What is the "2pq" in hardy-weinberg?
probability of being a heterozygote.
271
What is the "q^2" in hardy-weinberg?
probability of being homozygous recessive.
272
What is the "q^2" in hardy-weinberg?
probability of being homozygous recessive.
273
Why is the polymerase chain reaction technique useful?
we can make a lot of copies of a fragment of DNA.
274
What are the three main steps of the polymerase chain reaction?
denaturation, primer annealing, primer extension.
275
DNA cloning
identical copies of piece of DNA.
