Nucleotides in DNA and RNA are linked together by a phosphodiester bond.
The lactose binds to the repressor protein, changing its conformation to an inactive form, causing it to fall off the operator and allowing transcription to occur.
Different exons may code for different domains of a protein.
They isolated proteins, lipids, and nucleic acids, but only nucleic acids could transform R cells into pathogenic S cells.
Chromatin is DNA complexed with protein.
Replication is semiconservative.
Nucleotides are attached by phosphodiester linkage.
Meselson and Stahl
Tryptophan binds to the repressor protein at its allosteric site, causing a conformational change that activates the repressor, which then binds to the operator and turns off the operon, inhibiting transcription.
The lac operon produces the enzyme beta-galactosidase, which cleaves lactose into glucose and galactose.
Free and bound ribosomes.
No, the end-replication problem only affects linear DNA and does not occur in circular prokaryotic chromosomes.
Activators.
Distal control elements.
It consists of about 20 hydrophobic amino acids.
They used T2 bacteriophage to infect E. coli.
The genetic code is redundant but not ambiguous.
The three sites of a ribosome are: P-site (peptidyl-tRNA containing the growing polypeptide), A-site (aminoacyl-tRNA carrying the next amino acid), and E-site (exit site containing empty tRNA).
Spontaneous mutations are errors that occur during replication or repair, as well as DNA recombination, such as crossing over during prophase I of meiosis.
Deoxyribonucleic Acid (DNA)
Met - Trp - Phe - Gly - Arg - Phe
Linear
The operon was discovered by Jacob and Monod.
General and specific transcription factors are DNA binding proteins.
15 N
mRNA is read in the 5’ to 3’ direction during elongation.
In the lac operon, the repressor is synthesized in its active form, whereas in the trp operon, the repressor is activated by the presence of tryptophan.
The trp operon produces all the enzymes involved in the production of tryptophan.
The mRNA sequence is AUG U AGUUUGGCUAA.
The binding of co-repressor (tryptophan) is reversible and allosteric, leading to the active conformation of the repressor that binds to the operator.
When a DNA strand and an mRNA strand are hybridized together, they form a DNA-RNA hybrid molecule. This hybridization is crucial for processes such as transcription, where mRNA is synthesized from a DNA template.
The repressor protein binds to the operator to inhibit transcription when the operon is off.
Introns may contain sequences that regulate gene expression.
Ribonucleotides are added to the 3’ end, with synthesis occurring from 5’ to 3’.
mRNA and DNA are released immediately, and mRNA is ready for translation.
5' - AUG UGGUUUGGCCGUUUU UAA - 3'
Transcription
The trp operon consists of a promoter, an operator, and five structural genes (trpE, trpD, trpC, trpB, and trpA) that encode enzymes for tryptophan biosynthesis.
The lac operon is an inducible operon.
DNA methylation involves the addition of methyl groups to cytosine residues, resulting in the inactivation of genes and preventing their transcription, as seen in Barr body formation during X-chromosome inactivation.
The three main steps are initiation, elongation, and termination.
At the promoter of all genes.
The repressor protein is synthesized in its inactive form.
Liver cells produce activators that bind to the control elements of the albumin gene.
The inactive conformation of the repressor does not bind to the operator.
A silent mutation has no effect on the amino acid sequence due to redundancy in the genetic code.
Enzymes of a particular pathway coded for on different chromosomes, each with identical control elements recognized by a single type of transcription factor, leading to simultaneous transcription.
A point mutation is a type of small scale mutation where a single nucleotide is changed, inserted, or deleted in the DNA sequence.
The photo shows telomeres on mouse chromosomes, stained with fluorescent orange dye.
DNA polymerase can only add nucleotides to the 3’ end of a preexisting polynucleotide, leading to shorter DNA with each replication.
Prokaryotic DNA is less structured and folded than eukaryotic DNA.
It is a form of RNA processing that allows for the production of different protein variants from a single gene.
Uncontrolled gene expression can lead to serious diseases such as cancer.
cAMP binds to CAP, activating it to bind upstream of the lac promoter, increasing RNA polymerase affinity for the promoter.
After 20 and 40 minutes
The DNA sequence is T A A T C A.
DNA replication is the duplication of DNA where parental strands serve as templates for new strands, ensuring correct base pairing to create an identical double helix.
Structural genes are the non-regulatory genes that code for all the enzymes in a pathway and are clustered together.
The regulatory gene is located upstream of the promoter and is not considered part of the operon.
When the operon is on, RNA polymerase binds to the promoter, leading to transcription and the production of one long mRNA.
DNA polymerase III works in a direction away from the replication fork.
A nonsense mutation changes a codon to one of the three stop codons, resulting in a shorter and usually non-functional protein.
Steroid hormones bind to receptors, and the steroid-receptor complex activates a number of genes.
They signal termination of protein synthesis.
Not found in a nucleus.
The direction of transcription is called downstream, while the opposite direction is termed upstream. The promoter sequence in DNA is upstream from the terminator, and the stretch of DNA downstream from the promoter that is transcribed into an RNA molecule is called the transcription unit.
The 5' cap, a modified guanine nucleotide added to the 5' end, protects against degradation and aids attachment to ribosomes.
The non-template strand of DNA is sometimes called the coding strand, as its sequence will be identical to the mRNA (except U instead of T).
Point mutations are changes in one base pair in a single gene.
The operon provides control of gene expression in prokaryotes.
It allows a cell to express only a small fraction of its genes, which is essential for cellular differentiation and proper development.
The concentration of cAMP increases, which binds to catabolite activator protein (CAP).
14 N
A nonsense mutation occurs when the new codon is a stop codon, leading to premature termination of translation and a truncated protein.
Distal control elements are grouped together into a stretch of DNA called the enhancer.
One distal control element is common to both the albumin and crystallin genes.
90% of the cell cycle consists of interphase.
Distal control elements are grouped together in enhancers and may be thousands of nucleotides away from the promoter, upstream or downstream, and can even be in introns.
Heterochromatin is the highly condensed form of chromatin where genes cannot be transcribed.
T2 bacteriophages are comprised of DNA and protein.
Some amino acids are encoded by 1 codon, while others can be encoded by 2, 4, or 6 codons.
AUG
Prokaryotic DNA is smaller than eukaryotic DNA.
The SRP recognizes the signal peptide and brings the ribosome to a receptor on the ER membrane.
Telomeres shorten in somatic cells of older individuals, which can lead to the possible deletion of genes.
To determine whether DNA or proteins are the genetic material of bacteriophages.
5’ to 3’
The processes of transcription and translation are similar, but eukaryotic RNA polymerase requires transcription factors and eukaryotic mRNA must be processed, while in prokaryotic cells, transcription and translation are coupled.
1) Single-nucleotide pair substitution (point mutation) 2) Nucleotide pair insertions or deletions.
32 P DNA was found in the bacterial pellet.
RNA polymerase unwinds the DNA in the 5' to 3' direction.
They guide the linking of nucleotides to the growing DNA strand.
DNA replication begins with a short stretch of ribonucleotides called the RNA primer.
2 hydrogen bonds.
It is the process where the production of protein may be stopped or enhanced in response to environmental changes.
E. coli will preferentially utilize glucose.
Gene amplification is the temporary increase in the number of copies of a gene, leading to multiple copies of a single gene, such as the rRNA gene in amphibians during ovum development.
In the absence of lactose, the repressor protein is synthesized in its active form and binds to the operator to prevent transcription, keeping the operon OFF.
The trp operon is a repressible operon.
Nucleosomes are partially unfolded chromatin, described as beads on a string.
DNA is transcribed into RNA, which is then translated into protein.
Each amino acid has a specific aminoacyl-tRNA synthetase that attaches it to the corresponding tRNA, and this process is endergonic.
The three phases of interphase are G1 (cell growth), S (DNA replication), and G2 (preparation for cell division).
Introns allow for alternative splicing, enabling different portions of RNA to act as exons, leading to the construction of multiple polypeptides from a single transcript.
The active transcription complex is formed by the activator, enhancer, and RNA polymerase, along with general transcription factors and mediator proteins at the promoter.
Prokaryotes don’t have this problem because they have circular DNA.
Mutagens are physical or chemical agents that interact with DNA and can cause mutations.
Ribonucleic Acid (RNA)
A typical tRNA molecule is about 90 nucleotides long.
After binding, protein synthesis continues, with secreted proteins remaining in the ER lumen and membrane proteins embedded in the ER membrane.
One type
The promoter region includes the start point and the TATA box.
They read from 3' to 5'.
Type II
DNA ligase
A free 3’ OH group and small primers
In an antiparallel fashion.
It makes the two strands complementary.
A nuclease enzyme removes the defective portion of DNA during the repair process.
Translation is the synthesis of a polypeptide directed by mRNA.
Nucleotides are comprised of a nitrogen-containing base (purine or pyrimidine), a pentose sugar (5 carbon backbone), and a phosphate group attached to C5' of the sugar.
A complete initiation complex requires RNA polymerase, general transcription factors, mediator proteins, and specific transcription factors (activators) bound to control elements.
Activators enhance transcription, while repressors inhibit transcription.
Polyribosomes occur in both prokaryotes and eukaryotes, allowing multiple ribosomes to translate the same mRNA simultaneously.
The repressor protein is inactive and does not bind to the operator, allowing the operon to be turned on and mRNA to be produced.
Centrifugation
Polyribosomes enable one mRNA to make many copies of a polypeptide because several ribosomes can translate the same mRNA at once.
Enzymes of the tryptophan synthesis are repressible and their synthesis is repressed by an end product, while enzymes of the lactose pathway are inducible and their synthesis is induced by allolactose.
The final structure of mRNA is a single-stranded molecule that includes a 5' cap, a coding sequence, and a poly-A tail at the 3' end.
It leads to increased gene expression, demonstrating positive regulation.
This can lead to major problems, depending on the location in the protein.
Histone acetylation involves the attachment of an acetyl group to histone proteins, altering their conformation so that DNA binds less tightly, allowing transcription factors easier access to genes.
Specific transcription factors, also known as activators, determine which genes are expressed in a cell.
1) General transcription factors: bind at the promoter of all genes. 2) Specific transcription factors (activators): bind to distal control elements.
On free ribosomes.
Secreted or membrane proteins.
The amino acids are Met, Lys, Phe, Gly.
The reading frame of the mRNA will be altered, causing all downstream nucleotides to be misgrouped, which leads to a completely incorrect protein sequence.
Control elements help to position the initiator complex on the promoter.
During mitosis, nucleosomes undergo high-order packing, forming highly condensed chromosomes, leading to inhibition of transcription.
Eukaryotic chromosomes contain hundreds to thousands of origins of replication.
Proximal control elements are located close to or within the promoter.
The two forms of chromatin during interphase are euchromatin and heterochromatin.
Euchromatin is the uncondensed form of chromatin where genes can be easily transcribed.
Elongation factors and GTP are required for the elongation process.
Both pathways exhibit negative control because the operon is switched off by an active repressor.
The end-replication problem refers to the issue that occurs during the replication of linear DNA, where the ends of the DNA strands cannot be fully replicated, leading to potential loss of genetic information.
Bacterial DNA has only one origin of replication.
It directs the ribosome to become attached to the endoplasmic reticulum.
At the N-terminus.
Eye cells produce activators that bind to the control elements for the crystallin gene.
Exon shuffling may allow for the formation of new and possibly beneficial proteins.
Small scale mutations refer to changes in the DNA sequence that affect a small number of nucleotides, including point mutations.
Alternative splicing can significantly increase the number of different protein products, allowing an organism to produce more proteins than it has genes; for example, a human cell can synthesize 75,000 proteins from 20,000 genes.
Yes, the genetic code is universal for all life forms.
It continues for 10 to 35 bases after AAUAAA, and must be processed after being released with DNA.
Telomeres, which are repeats of short noncoding nucleotide sequences, protect genes from erosion at the ends of DNA molecules.
The termination codon reaches the A-site, a release factor binds to the codon, hydrolysis of the peptide bond occurs between tRNA and the polypeptide chain, the polypeptide is released, and the ribosome dissociates.
A large amount of proteins.
DNA pol I replaces the RNA with DNA.
DNA ligase forms a bond between the fragments.
The Smooth (S) strain is encapsulated with a polysaccharide coat and is pathogenic.
The three main steps of translation are Initiation, Elongation, and Termination.
There are 100 DNA repair enzymes in E. coli and 130 identified in humans.
To maintain the accuracy of DNA replication and prevent errors that could lead to mutations.
Anticodons are written 3' to 5'.
The leading strand has one primer, while the lagging strand has many primers.
The operator acts as an on/off switch for the operon.
They lead to the addition or loss of nucleotides in a gene.
Nucleotide triplets specify amino acids.
The first step is the binding of the activator protein to distal control elements within the enhancer.
A missense mutation leads to a change in the amino acid sequence, and the harm caused depends on whether the new amino acid has similar or very different properties from the original.
The heat shock response, where an increase in temperature activates genes coding for heat shock proteins that stabilize and repair heat-damaged proteins.
The template strand is read in the 3’ to 5’ direction.
The mRNA codon forms hydrogen bonds with the anti-codon of the incoming tRNA.
Transcription
Frederick Griffith studied Streptococcus pneumonia, focusing on two strains: Smooth (S) which is pathogenic and Rough (R) which is harmless.
DNA polymerase proofreads each nucleotide added and removes incorrect pairings before resuming synthesis.
There are 61 mRNA codons, but there are only about 45 tRNAs due to the wobble effect.
A mutation is a change in the genetic material of a cell.
Proteins bind to origins of replication, causing DNA to unwind and form replication bubbles.
The new strand is synthesized from 5' to 3'.
Initiation requires initiation factors and GTP, along with the binding of the small ribosomal subunit to mRNA.
Helicase unwinds and separates the parental DNA strands.
DNA: CTA CTT, mRNA: GAU GAA, resulting in aspartic acid and glutamic acid (both have negative charge).
The sugar-phosphate backbone.
Individuals with Xeroderma Pigmentosa lack the functional DNA excision repair enzyme.
Introns increase the likelihood of crossing over by providing more DNA length, allowing for crossovers between the exons of alleles without interrupting coding sequences.
Elongation occurs in the 5’ to 3’ direction.
DNA bends (hairpin) facilitated by bending proteins.
Harmful chemical and physical agents, such as cigarette smoke and x-rays, as well as spontaneous changes in DNA.
Changes in DNA that occur in germ cells must be corrected before they become permanent mutations.
Circular
The growing polypeptide is transferred from the tRNA in the P-site to the tRNA in the A-site, forming a peptide bond between the amino terminus of the new amino acid and the carboxyl end of the growing polypeptide.
DNA pol III detaches after reaching the next RNA primer to the right.
Functions in the synthesis of proteins
Translation
Mismatch repair occurs when an error has not been detected by DNA polymerase, involving enzymes other than DNA polymerase.
They bind tightly to the negatively charged DNA.
The sequence of the TATA box on the template strand is ATATTTT.
Topoisomerase helps relieve the strain of untwisting the helix by breaking, swiveling, and rejoining the DNA strands.
A double helix.
After initiation, the initiator tRNA is located in the P-site of the ribosome.
10 bases.
Exon shuffling can lead to new proteins with novel combinations of functions by mixing and matching exons between different genes.
Ribosomal RNA (rRNA) is associated with protein to form ribosomes, which are essential for protein synthesis.
Pre-mRNA modification occurs in eukaryotic cells before mRNA leaves the nucleus.
TTATTT on template DNA, which becomes AAUAAA on mRNA.
The diagram shows the differences, which include modifications that pre-mRNA undergoes to become mature mRNA.
Primase joins RNA nucleotides into a primer.
The growing polypeptide in the A-site is moved to the P-site, the next codon arrives in the A-site, and the empty tRNA moves from the P-site to the E-site and exits the ribosome.
The transcription unit is the stretch of DNA downstream from the promoter that is transcribed into an RNA molecule.
The poly A tail, consisting of 50 to 200 adenines added to the 3' end, protects against degradation, aids attachment to ribosomes, and facilitates transport out of the nucleus.
Griffith concluded that the living R bacteria had been transformed into pathogenic S bacteria by an unknown heritable substance from the dead S cells.
3’ to 5’
Discontinuous synthesis as a series of short Okazaki fragments
DNA polymerase III (pol III)
5’ to 3’ direction
The anti-codon UAC of the tRNA containing methionine base pairs with the start codon (AUG) on the mRNA during translation initiation.
In the 3’ to 5’ direction
A thymine dimer is a change in DNA caused by the cross-linking of thymine residues, which can occur as a result of sun exposure.
Pre-mRNA modification is required for transport, stability, and recognition before mRNA leaves the nucleus.
Telomerase is not active, or is only slightly active in human somatic cells.
A frameshift mutation occurs when nucleotides are inserted or deleted from a gene in a number that is not a multiple of three, leading to improper grouping of subsequent nucleotides into codons.
Germ cells are the cells that lead to gametes.
tRNA brings amino acids to the ribosome and contains an anti-codon complementary to the codon on mRNA.
Ribosomal RNA (rRNA), Transfer RNA (tRNA), Messenger RNA (mRNA)
RNA polymerase
RNA polymerase binds to the promoter region of DNA and unwinds it to initiate transcription.
Chromatin (DNA wound around histones).
Messenger RNA (mRNA) serves as the template for protein synthesis.
Introns are non-coding sequences transcribed but not translated; they are removed during RNA splicing before mRNA exits the nucleus.
Watson and Crick
It was concluded that DNA, not protein, is the genetic material of bacteriophages.
A neutral (conservative) mutation is when the new amino acid has similar properties to the original.
Sense strand, coding strand, and non-template strand are all the same thing.
3 hydrogen bonds.
DNA ligase seals the gap after the correct nucleotides are added.
DNA pol III adds DNA nucleotides to the primer, forming an Okazaki fragment.
Double stranded
The enzyme telomerase lengthens telomeric DNA in eukaryotic germ cells to prevent the loss of important genes during gamete production.
Three types
Excision repair is a type of DNA repair that occurs after replication.
They play a key role in chromatin structure.
By linking the phosphate of one nucleotide with the sugar of the next.
Primers are short segments of RNA complementary to template DNA, made by an enzyme called primase.
Hydrogen bonds between bases on the two chains.
The wobble effect refers to the flexibility in the binding between the third base of the mRNA codon and the corresponding base in the tRNA, allowing for fewer tRNAs than codons.
The result was that mice died, and living S cells were found in the blood of the dead mice, indicating that R cells were converted to a pathogenic form.
1) DNA polymerase proofreading, 2) Mismatch repair.
Small proteins rich in positively charged amino acids: arginine and lysine.
35 S proteins were found in the supernatant.
The Rough (R) strain lacks a coat and is harmless.
It undergoes processing before being translated into protein.
During initiation, the initiator tRNA binds to the start codon (AUG) on the mRNA, and the large ribosomal subunit attaches, requiring GTP.
3’ (OH) end
Yes, Okazaki fragments are present in both.
If a protein does not contain a signal peptide, the ribosomes remain free in the cytoplasm.
RNA splicing removes introns (non-coding sequences) from pre-mRNA and links exons (coding sequences), accomplished by spliceosomes where RNA acts as a ribozyme.
The sequence of the TATA box on the non-template strand is TATAAAA.
There are two replication forks at each replication bubble.
mRNA looks like the non-template strand except that U replaces T.
mRNA feeds through the ribosome from 5' to 3'.
Deoxyribonucleotides are replaced by DNA polymerase I.
No, pol III is for prokaryotes only; the situation in eukaryotes is more complex.
Correct nucleotides are added by a DNA polymerase after the defective portion is removed.
35 S radiolabeled proteins.
In prokaryotes, transcription and translation are coupled because there is no nucleus.
Pre-mRNA
A silent mutation is a change that results in no change in the amino acid sequence.
DNA: CCG CCA, mRNA: GGC GGU, resulting in glycine and glycine.
Single stranded binding proteins bind to the unpaired DNA strands, keeping them from re-joining.
The ribonucleotides in the RNA primer can hydrogen bond with the complementary deoxyribonucleotides in the DNA strand.
Individuals with Xeroderma Pigmentosa have high rates of cancer if exposed to the sun.
