DNA & Protein Synthesis Flashcards
(140 cards)
1
Q
Define Gene Expression
A
The process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce protein as the end product.
2
Q
Define Central Dogma
A
The process by which the instructions in DNA are converted into a functional product.
3
Q
Define Degeneracy
A
The property of the genetic code that allows multiple codons to code for the same amino acid.
There are 64 possible codons and only 20 relevant amino acids. Codons for the same amino acid often differ in their third base.
4
Q
Define Nucleic Acid
A
An organic molecule present in living cells, especially DNA or RNA, consisting of a chain of nucleotides.
5
Q
Define Nucleotide
A
An organic molecule that is the building block of DNA and RNA. Made up of a phosphate group, a 5-carbon sugar, and a nitrogenous base.
6
Q
Define Nitrogenous Base
A
Molecules that serve as main components of DNA and RNA. All contain nitrogen and display basic properties. The nitrogenous bases used in normal nucleus acids are adenine, guanine, cytosine, thymine, and uracil.
7
Q
Define DNA Replication
A
The process by which DNA makes a copy of itself, necessary for cell reproduction prior to division.
8
Q
Define Telomere
A
A repeating, non-coding sequence at the end of the chromosomes, thought to protect the DNA from degradation.
Telomeres shorten over time, a process that may be connected to aging and the medical problems that come with it.
9
Q
Define Transcription
A
The process of copying a gene from DNA into mRNA.
10
Q
Define mRNA
A
Messenger RNA. mRNA is a single stranded molecule of RNA that is the product of DNA transcription. It corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. It is short-lived in the cell, as its function is to be translated into protein. It cannot replicate itself and must be transcribed from DNA.
11
Q
Define Splicing as it relates to transcription
A
Splicing is a form of RNA processing in which a newly made mRNA transcript is edited so that it can be translated into a protein. This process removes non-coding regions (introns) and joins together exons (coding regions). It is carried out by the spliceosome.
12
Q
Define Exon
A
A segment of DNA or RNA that contains information coding for a protein or peptide sequence.
13
Q
Define Intron
A
A non-coding segment of DNA or RNA that is eliminated by splicing before translation.
14
Q
Define Translation
A
The process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins from the information contained in mRNA.
15
Q
Define Ribosome
A
An organelle consisting of rRNA and associated proteins that translates mRNA into proteins.
16
Q
Define tRNA
A
Transfer RNA. It is an adapter molecule that serves as the physical link between the mRNA and the amino acid sequence of proteins. On one end of a tRNA is an amino acid. On the other end is a specific sequence of nitrogenous bases.
17
Q
Define rRNA
A
Ribosomal RNA. It is a type of non-coding RNA that carries out protein synthesis, and is the main component of ribosomes.
18
Q
Define Codon
A
A block of three nucleotides that codes for an amino acid.
19
Q
Define Mutation
A
An alteration in the DNA sequence. Mutations can arise spontaneously (often from errors in DNA replication) or be induced by mutagenic substances.
Mutations never arise in response to selective pressure.
20
Q
Define Point Mutation
A
A mutation affecting a single nucleotide base.
21
Q
Define Substitution Mutation
A
A mutation where one base is replaced with a different base.
22
Q
Define Missense Mutation
A
A point mutation in which a single nucleotide change results in a codon that codes for a different amino acid.
23
Q
Define Nonsense Mutation
A
A point mutation in which a single nucleotide change results in a premature stop codon.
This usually results in a shortened and likely non-functional protein.
24
Q
Define Chromosomal Mutation
A
A mutation that affects whole molecules of DNA, rather than just a few bases.
Chromosomal mutations are typically the result of errors that occur during meiosis, or of mutagens.
25
Define Deletion (Chromosomal Mutation)
A chromosomal mutation in which a part of a chromosome is left out during DNA a replication and is lost.
26
Define Inversion (Mutation)
A chromosomal mutation in which a nucleotide sequence is completely reversed.
27
Define Translocation (Mutation)
A chromosomal mutation in which a nucleotide sequence moves to another position, either within the same or between different chromosomes.
28
Define Duplication (Mutation)
A chromosomal mutation in which part or all of a chromosome is repeated.
29
Define Frameshift Mutation
A mutation caused by indels of a number not divisible by three, shifting the three codon “frame” in which the sequence is read.
30
Define Insertion (Mutation)
The addition of one or more nucleotides; a point mutation.
31
Define Deletion (Mutation)
The removal of one or more nucleotides; a point mutation.
32
Define Silent Mutation
A mutation that does not have an observable effect on the organism’s phenotype.
33
Define Mutagen
A chemical or other substance that induces changes in DNA.
Mutagens are item also categorized as carcinogens, or cancer-causing substances.
34
Define Paralogous
Relating to genes that arose from a common ancestral gene by gene duplication in the course of evolution.
35
Define Pseudogene
A gene that loses its protein producing abilities or stops being expressed.
Genes become pseudo genes when they accumulate mutations over a long time. This only happens if the mutations do not compromise the organism’s survival; otherwise natural selection would eliminate the mutations.
36
What were Chargaff’s rules?
1) All species have different amounts of adenine, thymine, cytosine, and guanine in their DNA
2) In every species:
amount of adenine=amount of thymine
amount of cytosine=amount of guanine
37
What biological role is played by nucleic acids?
They store genetic material in the form of DNA, allowing it to be inherited. They also direct the formation of protein through translation from mRNA transcripts.
38
Describe the structure of double stranded DNA
Double stranded DNA forms a double helix. Two complimentary strands are held together in a twisting, or helical, shape. The strands are antiparellel, meaning they run in opposite directions. They are composed of nucleotides, or nitrogenous bases held together by a sugar phosphate backbone.
39
What is the relationship between histones, nucleosomes, and chromatin?
Histones are small proteins that form core complexes around which DNA warps tightly. A nucleosome includes a histone core and its associated DNA. These structures are present in chromatin, the tightly packed organizational structure that forms chromosomes.
40
What electric charge exists on DNA molecules?
A negative charge. This charge comes from the sugar-phosphate backbone, specifically the phosphate ion.
41
How are the ends of a DNA strand denoted?
5’ and 3’
The 5’ end contains an unbound phosphate group, while the 3’ end contains a free -OH.
42
Towards which electrode, the anode or cathode, will DNA migrate in gel electrophoresis?
The DNA will migrate toward the anode. The anode is positively charged, while the cathode is negatively charged. Since DNA is negatively charged, it will migrate toward the positively charged electrode.
43
What is the difference between a nucleotide and a nucleoside?
A nucleoside is a nucleotide without any phosphate groups. A nucleoside contains a nitrogenous base and a sugar molecule.
44
Give two examples of nucleotides with non-genetic functions
```
Adenosine Triphosphate (ATP)—a source of energy produced in cellular metabolism.
Cyclic AMP (cAMP)—a signaling molecule involved in second messenger cascades.
Other examples include GTP and modified nucleotides like NADH and FADH2.
```
45
Which base pair has stronger bonds?
The cytosine guanine pair has stronger bonds because it contains three hydrogen bonds, while the adenine thymine pair has two hydrogen bonds.
46
Researchers observe that DNA strand A denatures at a lower temperature than DNA strand B. Which property of the two strands might determine this result?
Strand A likely has a higher content of adenine and thymine bases, while strand B has more cytosine and guanine bases.
This property is referred to as GC content. Strands with more G and C bases will denature around a higher temperature because the three hydrogen bonds between guanine and cytosine form a stronger connection than the two between adenine and thymine.
47
What are the major differences between DNA and RNA?
RNA is a single stranded molecule, while DNA is double stranded. The sugar in RNA is ribose, which has one more oxygen atom than deoxyribose, found in DNA. RNA contains uracil instead of thymine.
48
Name the two main types of chromatin found in eukaryotic cells
Euchromatin and heterochromatin.
Euchromatin is loosely packed and appears light-colored when viewed under a microscope.
Heterochromatin is more dense, or tightly packed, and appears darker.
49
Bases on the same strand are ___________ bonded to each other by ________________ bonds.
covalently, phosphodiester
50
Which type of chromatin is likely to be more prevalent in genes that are actively being transcribed?
Euchromatin
Because it is more loosely wound, euchromatin allows enzymes like RNA polymerase access to the nucleotide structure. In contrast, the density of heterochromatin protects the DNA when it is not being transcribed.
51
Which nitrogenous bases does DNA contain?
Adenine, guanine, cytosine, and thymine. Adenine pairs with thymine and cytosine pairs with guanine.
52
Bases on opposite strands are _____________ bonded to each other.
hydrogen
53
Which nitrogenous bases does RNA contain?
Adenine, guanine, cytosine, and uracil. Adenine pairs with uracil and cytosine pairs with guanine.
54
Name the three main types of RNA
mRNA, tRNA, and rRNA
mRNA is a template that gets translated into a protein, tRNA carries the amino acids to the ribosome to be assembled, and rRNA is a main structural component of ribosomes.
55
Which two major groups are nitrogenous bases categorized into?
Purines (adenine and guanine) and pyrimidines (cytosine, thymine, and uracil).
56
What are the similarities and differences between purines and pyrimidines?
Similarities: contain one or more nitrogenous heterocyclic rings, major component of DNA and RNA
Differences: pyrimidines consist of a single six membered ring that contains two nitrogens, while purines consist of two fused rings, one pyrimidine ring and one five membered imidazole ring.
57
Which is more likely to be harmful, a base base substitution or a frameshift mutation?
A frameshift mutation has higher potential to adversely affect the organism.
A single base substitution changes at most one codon. At worst, a stop codon could be prematurely added and the protein ended early.
A frameshift mutation causes the entire reading frame after the mutation to be moved. This may alter many amino acids, resulting in a drastically different or non-functional protein.
58
Which is more likely to be harmful, a missense or nonsense mutation?
A nonsense mutation has higher potential to adversely affect the organism.
A missense mutation changes only a single amino acid.
A nonsense mutation causes the translation process to be prematurely stopped, resulting in a shortened and often non-functional protein.
59
What are trinucleotide repeats, and what kind of mutation can they lead to?
Sequences of three nucleotides repeated several times. This can easily to repeat expansion, or an increase in the number of repeats due to an error during DNA replication. The repeat expansion creates a new allele, but the protein still functions. However, when the number of repeats exceeds the “normal” threshold for the gene, the protein no longer functions properly.
60
When in the cell cycle do most chromosomal alterations that affect chromosome structure occur?
The S phase, when DNA is replicated.
During prophase I of meiosis, when crossing over occurs.
Upon exposure to damaging agents such as radiation.
61
What are the four types of alterations that affect chromosome structure?
Translocation, deletion, duplication, inversion.
62
Gene duplication outcomes
* one of the two gene copies can lose its function by accumulating mutations over generations
* one of the two gene copies can gain a novel function through subsequent mutations (this only occurs if the original gene duplication event does not severely affect the organism and persists over generations)
* the two copies of the gene split the total function of the ancestral gene into two unique but related functions for more efficient expression
63
What two types of mutations lead to a frameshift?
Insertion and deletion
64
What two situations could lead to a silent mutation?
* A mutation in an intron
| * A mutation that replaces one degenerate codon with another
65
What is PCR?
PCR (Polymerase Chain Reaction) is a technique that enables the production of millions of copies of a specific DNA sequence from an initially small sample.
66
What are the three steps involved in PCR?
1) Denaturation: heating separates the two DNA strands, making them available for replication.
2) Annealing: Specific primers attach to the DNA strands, specifying the location to be replicated.
3) Extension: free nucleotides are added to the growing strand by a polymerase, usually one acquired from a thermostable bacterium.
67
After several rounds of PCR, 16 molecules of DNA are present. How many molecules should exist after two more rounds?
64. Each additional round of PCR should double the existing number of DNA strands. 2^n strands will be present after n rounds of replication.
68
What laboratory function is performed by restriction enzymes?
Restriction enzymes, also called endonucleases, cut DNA strands at specific sequences.
In genetic research, they are used to cut DNA for later sequencing or manipulation. These enzymes are generally isolated from bacteria, where they serve a protective function by cleaving foreign DNA.
69
Which way are DNA bases “read” and which way are they synthesized?
Bases are read in the 3’ to 5’ direction. They are synthesized in the 5’ to 3’ direction.
70
Upstream means in the ___ to ___ direction, and down stream means in the ___ to ___ direction.
5’, 3’; 3’, 5’
71
How are deoxyribose sugars numbered?
Clockwise, starting from the oxygen atom.
72
What is the base sequence for the start codon?
AUG, codes for the amino acid methionine.
73
What are the three possible base sequences for the stop codon?
UGA, UAA, or UAG
74
Which organelles are involved in synthesizing proteins?
Nucleus, ribosomes, endoplasmic reticulum, golgi apparatus, vesicles.
75
What broad name is given to enzymes that add nucleotides onto a growing amino acid strand?
Polymerases
While a variety exist in both prokaryotes and eukaryotes, those that synthesize DNA are broadly know as DNA polymerases, while those that synthesize RNA are known as RNA polymerases.
76
In eukaryotes, one mRNA transcript codes for exactly one polypeptide molecule. What name is given to this characteristic, and what is its opposite?
Eukaryotic mRNA is monocistronic, while prokaryotic mRNA is polycistronic.
Eukaryotic, but not prokaryotic, DNA undergoes post-transcriptional modification. After this, the mature mRNA contains the sequence for a single peptide. In contrast, a prokaryotic mRNA transcript can code for many proteins and includes multiple start and stop codons. Polycistronic means “many genes.”
77
When and why does DNA replication occur?
Before cell division so that each daughter cell has the same DNA as the parent cell.
78
Why is DNA replication said to be semi-conservative?
Because each of the two template strands becomes half of a new DNA double helix.
79
In the replication of a DNA strand, an adenine base is included instead of a cytosine. The rest of the strand is replicated normally. What type of mutation occurred?
A substitution mutation, because one base was replaced with another. This mutation can also be classed as a point mutation, since it only altered a single base.
80
What are the major enzymes involved in the DNA replication process?
Helicase, SSB, primase, DNA polymerase, ligase, sliding clamp, RNase H
81
Where does the energy for bonding in DNA replication come from?
Nucleotides arrive as nucleosides—DNA bases with P-P-P. These are three phosphates. When the bond between the phosphates is broken, the energy released is used to form a bond between the incoming nucleotide and growing chain. DNA bases arrive with their own energy source for bonding.
82
What are the three types of DNA replication?
Conservative: the parental double helix remains intact and an all new copy is made.
Semi-conservative: the two strands of the parental double helix separate, and each function as a template for synthesis of a new complimentary strand.
Dispersive: each strand of both daughter molecule contains a mixture of old and newly synthesized parts.
83
What is the function of helicase in DNA replication?
Helicase unwinds the DNA double helix into two individual strands.
84
What is the function of SSB in DNA replication?
SSB (Single-Stranded Binding Proteins) are tetrameres that coat the single stranded DNA to prevent reannealing.
85
What is the function of primase in DNA replication?
Primase is an RNA polymerase that synthesizes the short RNA primers needed to start the strand replication process.
86
Where are the enzymes involved in DNA replication found?
In the nucleus.
87
What is the function of DNA polymerase in DNA replication?
DNA polymerase is an enzyme that strings nucleotides together to form a DNA strand.
88
What is the function of ligase in DNA replication?
Ligase links short stretches of DNA together to create one long continuous DNA strand.
89
What is the function of the sliding clamp in DNA replication?
The sliding clamp is an accessory protein that helps hold the DNA polymerase onto the DNA strand during replication.
90
What is the function of RNase H in DNA replication?
RNase H removes the RNA primers that previously began the DNA strand sequence.
91
What is a replication fork?
The point where the DNA is separated into single strands and where new DNA will be synthesized.
92
What is the function of telomerase in DNA replication?
Telomerase is an enzyme that extends telomeres. It can add DNA bases at the 5’ end.
93
Why can DNA polymerase only synthesize in a 5’ to 3’ direction?
DNA polymerase hooks the 5’ phosphate group of an incoming nucleotide to the 3’ hydroxyl group at the end of the growing nucleus acid chain. The chain grows by extension off the 3’ end.
94
What is the function of topoisomerase in DNA replication?
Topoisomerase relieves supercoiling, or strain cause by excess twisting of the DNA helix, by breaking the sugar phosphate backbone, unwinding, and reannealing.
This is necessary because as helicase unzips the double stranded DNA, the region ahead of the replication fork becomes supercoiled.
95
How is the RNA primer removed?
RNase H recognizes RNA DNA hybrid helices and degrades the RNA by hydrolyzing its phosphodiester bonds.
96
Why can’t DNA polymerase jump right in and begin copying?
It can extend a nucleus acid chain, but can’t start one from scratch.
97
DNA polymerase III vs. DNA polymerase I
DNA polymerase III: the main DNA builder
| DNA polymerase I: proofreading, editing, repair, and primer removal
98
The _________ strand is copied continuously, while the __________ strand is copied in a series of fragments.
leading, lagging
99
What modification is made to DNA for the purpose of mismatch repair?
Methylation, or the addition of a methyl group, helps DNA polymerase distinguish between the parent strand and the newly synthesized strand. This is important because DNA polymerase must correct the base on the new strand, not the sequentially correct parent strand.
100
Why is the lagging strand synthesized differently?
Both strands are drawn through the factory in the same direction. The strands are antiparallel and can only be synthesized in the 5’ to 3’ direction, so DNA polymerase must keep jumping back and synthesizing one small segment at a time.
101
What features distinguish the leading and lagging strands?
The leading strand points toward the replication fork when read 5’ to 3’. It is synthesized continuously as the fork opens in front of it, since DNA polymerase can only add nucleotides to the 3’ end.
The lagging strand points away from the replication fork when read 5’ to 3’. It is synthesized discontinuously in a series of Okazaki fragments that are later joined by DNA ligase.
102
How is the lagging strand synthesized?
The lagging strand is synthesized discontinuously in a series of fragments called Okazaki fragments. RNA primase lays down short primer sequences. DNA polymerase extends each sequence and then jumps back to start another sequence each time it runs into a primer. The fragments are then joined by ligase.
103
What are Okazaki fragments?
Short sequences of DNA nucleotides on the lagging strand that are synthesized discontinuously and later linked together.
104
What are the steps of DNA replication?
The helicase enzyme unwinds the double helix to expose two single DNA strands and create two replication forks. DNA replication takes place simultaneously at each fork. The proteins involved in replication are clustered together and anchored in the cell, so the length of the DNA is drawn through the “station”. SSBs coat the single DNA strands to prevent reannealing. SSBs are easily displaced by DNA polymerase. The primase enzyme uses the original DNA sequence as a template to synthesize a short RNA primer. DNA polymerase begins to synthesize a new DNA strand by extending an RNA primer in the 5’ to 3’ direction. RNase H recognizes RNA primers bound to DNA templates and removes the primer by hydrolyzing the RNA. DNA polymerase then fills in the gap left by RNase H. The ligase enzyme joins the short pieces of DNA together into one continuous strand.
105
Where do transcription and translation occur?
Transcription occurs in the nucleus. Translation occurs in the ribosome located in the cytoplasm or membrane of the rough endoplasmic reticulum.
106
How does the transcription unit know where to begin?
There is a special sequence called the promoter. It’s nearly universal (TATAAAA) and helps the enzyme figure out where to bind to the strand.
107
What are the major enzymes involved in the transcription process?
RNA polymerase
108
What are the three RNA polymerase enzymes and their functions?
RNA polymerase I: only transcribes rRNA genes and makes ribosomes.
RNA polymerase II: transcribes genes into mRNA.
RNA polymerase III: only transcribes tRNA genes.
Each has a specific promoter sequence it recognizes.
109
What is the function of RNA polymerase in transcription?
RNA polymerase unzips and copies the DNA sequence downstream of the TATA box (3’ to 5’), assembling nucleotides into an mRNA strand. It rezips the DNA strand behind it. When it reaches another sequence , the termination signal, it is triggered to pull off.
110
What are the template and coding strands?
The transcribed strand is the template strand, and has the complimentary bases to the mRNA strand. The untranscribed strand is the coding strand, and has the same sequence as the mRNA strand.
111
What term is used to refer to the mRNA before it is edited?
Primary transcript
112
How do the terms sense strand, antisense strand, and template strand relate to the RNA strand initially produced during transcription?
The sense strand is the same as the RNA strand, but contains thymine instead of uracil. It is the strand of DNA that wasn’t used to produce the complimentary RNA strand.
The antisense strand is the strand of DNA that was transcribed into RNA. It is complementary to the new RNA strand, but contains thymine instead of uracil. The antisense strand is also called the template strand.
113
What edits must be made to the mRNA before it can leave the nucleus?
The 5’ cap is added to the 5’ end, and the poly-a tail (≈ 250 adenines) is added to the 3’ end. Introns are spiced out and exons joined together by the spliceosome.
114
How do post-transcriptional modifiers differ in prokaryotes and eukaryotes?
Prokaryotic mRNA does not undergo post-transcriptional modification.
Unlike in eukaryotes, where transcription and translation are distinct processes and occur in different locations, prokaryotic transcription and translation are simultaneous, and prokaryotes do not have introns.
115
What is the purpose of adding a 5’ cap and poly-a tail to the ends of the mRNA?
The caps make it easier for the mRNA to leave the nucleus, protect it from degradation from passing enzymes, and make it easier to connect with other organelles later on.
116
What is the function of the snRNPs in RNA splicing?
snRNPs (small nuclear ribonucleic proteins) are a combination of RNA and proteins that recognize the sequences that signal the start and end of the areas to be spliced. They bunch together with other proteins to form the spliceosome, which does the actual editing.
117
What is alternative splicing?
RNA can be spliced in different ways, with different segments treated as exons. Alternative mRNAs are produced from the same gene.
118
What are the steps of building a polypeptide?
Initiation: the ribosome, mRNA, subunits, and initiator tRNA are brought together.
Elongation: amino acids are added together based on the codon sequence of the mRNA.
Termination: the end codon is reached, and amino acid assembly stops.
119
What is the function of the nucleolus?
It builds ribosome subunits from rRNA and proteins. They exit through nuclear pores into the cytoplasm and combine to form functional ribosomes.
120
What are the two types of ribosomes?
Free ribosomes: suspended in the cytosol to synthesize proteins that function in cytosol.
Bound ribosomes: attached to the endoplasmic reticulum to synthesize proteins for export or for membranes.
121
Ribosomes: A site
The aminoacyl-tRNA site holds the tRNA carrying the next amino acid to be added to the chain.
122
Ribosomes: P site
The peptidyl-tRNA site holds the tRNA carrying the growing polypeptide chain.
123
Ribosomes: E site
The exit site is where the empty tRNA leaves the ribosome.
124
What are the steps of translation?
The mRNA slides through the ribosome, which reads the mRNA three bases at a time (codon). A tRNA with the complimentary bases (anticodon) is brought into the ribosome. The amino acid brought with it is assembled into a polypeptide chain.
125
Describe the structure of tRNA
tRNA has a clover leaf loop structure, with an anticodon inch one end and an amino acid attached on the 3’ end.
126
Genetic Medicine: Gene Therapy
An experimental technology that allows researchers to provide functioning copies of genes to cells with disease-causing versions of those genes. A common delivery method uses viral vectors, which infect the target cells and release its genome, including the therapeutic gene, inside.
127
How is an amino acid attached to a tRNA molecule?
The enzyme aminoacyl tRNA synthetase bonds the amino acid to the tRNA. This bond requires energy, which is stored unstably in the bond so it can be broken easily and release the amino acid at the ribosome.
128
How are peptide bonds between amino acids formed?
By the enzyme peptidyl transferase.
A new polypeptide chain is synthesized from its N (amino) terminal to its C (carboxyl) terminal.
129
After the ribosome has assembled the amino acids into a polypeptide chain, what happens to the new protein?
It is folded and assembled into a 3-dimensional functional protein. This processing takes place in the cytoplasm or the endoplasmic reticulum and golgi system.
130
Genetic Medicine: CRISPR Cas9
A technology that allows scientists to change a cell’s DNA at a precise location. It can be used to knock out a gene so that it isn’t expressed, or edit the gene to correct a disease-causing mutation.
131
Genetic Medicine: Gene Switches
A technology that targets noncoding, regulatory DNA sequences in the genome, referred to as gene switches, in order to alter gene expression. These switches bind regulatory proteins that turn the transcription genes on or off. This method can be used to prevent genes linked to diseases from being turned in, or to keep beneficial genes from being turned off.
132
Genetic Medicine: Exon Skipping
A technology that changes how the primary RNA transcript of a gene with a disease-causing mutation is spliced, removing the mutation from the resulting mRNA. Exon skippings allows a shortened but partially functional protein to be produced.
133
Genetic Medicine: Small Molecule Drug
A therapy comprised of a diverse group of chemical compounds with low molecular weight that are synthesized in the lab. These molecules can be easily taken up by cells, and may interact directly with disease-causing proteins, or through other molecules.
134
Genetic Medicine: RNA Interference
A technology that uses small RNA segments to target various mRNAs for destruction, reducing the expression of certain genes.
135
Friedrich Miescher
Discovered nucleus acids in 1869
136
Fredrick Griffith
A Scottish microbiologist who discovered transformation in 1928 by experimenting with bacteria and mice.
137
Avery, McCarty, & MacLeod
Refined Griffith’s experiment in 1944
138
Hershey & Chase
Worked with bacteriophages to conclusively demonstrate that DNA was the molecule of heredity in 1953.
139
Erwin Chargaff
An Australian biochemist who demonstrated two major rules of DNA composition. 1950-1952
140
Watson & Crick, Franklin & Wilkins
Two competing teams trying to determine DNA structure. Watson and Crick used X-ray diffraction data developed by Rosalind Franklin to develop their donor helix model of DNA. (1953)
