p.11
Chromatin Structure and Modification
What modification occurs to histones that decreases their positive charge?
Acetylation of free lysine residues.
p.12
Gene Regulation Mechanisms
How does DNA methylation suppress gene expression?
By blocking the binding of transcription factors and inducing heterochromatin formation.
p.3
Chromatin Structure and Modification
What is the result of successive levels of coiling in chromatin?
A highly condensed chromosome structure at mitosis.
p.12
Gene Regulation Mechanisms
What role does histone deacetylase play in DNA methylation?
It recognizes and binds to regions with methylated DNA, inducing histone deacetylation.
p.2
Translational Control of Gene Expression
What are the key components of translational control in eukaryotes?
Half-life of RNA and initiation of translation.
p.8
Role of Introns and Alternative Splicing
What role does the short RNA molecule in telomerase play?
It pairs with the telomere sequence to allow extension.
p.19
Translational Control of Gene Expression
How does the length of the 3' poly-A tail affect mRNA?
A longer poly-A tail acts as a buffer against degradation, allowing the mRNA to remain functional for more translation.
p.15
Gene Regulation Mechanisms
What are transcription factors?
Proteins that bind to specific DNA sequences, known as control elements, to control the rate of transcription.
p.7
Structure and Organisation of Eukaryotic Genome
How do telomeres maintain the integrity of chromosomal ends?
By preventing fusion of chromosomal ends with other chromosomes.
p.3
Chromatin Structure and Modification
What is linker DNA?
The remainder of the DNA not wound around histones that joins adjacent nucleosomes.
p.18
Role of Introns and Alternative Splicing
What is the significance of alternative splicing in the human genome?
It enables the synthesis of many more proteins than would be expected from its 20,000 protein-coding genes.
p.5
Transcriptional Control of Gene Expression
What is a promoter?
A specific nucleotide sequence located just upstream of a gene that initiates transcription.
p.18
Comparison of Gene Regulation in Prokaryotes and Eukaryotes
What post-transcriptional modifications occur in eukaryotes?
Post-transcriptional modifications, including alternative splicing, occur in eukaryotes.
p.20
Post-Translational Control of Gene Expression
What regulates the amount of a particular functional protein in a cell?
Post-translational modifications and protein degradation.
p.20
Post-Translational Control of Gene Expression
What is the purpose of post-translational modifications?
To form functional proteins through the addition of chemical groups.
p.14
Transcriptional Control of Gene Expression
What do general transcription factors bind to?
The promoter to initiate transcription at a basal rate.
p.10
Chromatin Structure and Modification
What is the result of the close packing of chromatin?
It prevents the formation of the transcription initiation complex.
p.2
Translational Control of Gene Expression
How does the half-life of mRNA affect gene expression?
It determines how long mRNA remains available for translation, influencing the amount of protein produced.
p.14
Transcriptional Control of Gene Expression
What is the role of specific transcription factors?
To bind to specific non-coding DNA sequences to regulate the rate of transcription.
p.20
Post-Translational Control of Gene Expression
What is hydroxylation and where does it occur?
The addition of hydroxyl groups, such as in collagen polypeptides forming hydroxyproline and hydroxylysine.
p.8
Role of Introns and Alternative Splicing
What is the function of telomerase reverse transcriptase (TERT)?
It uses the short RNA molecule as a template to extend the telomere length.
p.2
Structure and Organisation of Eukaryotic Genome
How do eukaryotic genomes differ from prokaryotic genomes?
Eukaryotic genomes are generally much larger and consist of linear chromosomes, while prokaryotic genomes are smaller and typically circular.
p.19
Translational Control of Gene Expression
What common mechanism do both prokaryotes and eukaryotes use to regulate translation initiation?
Both use translational repressors or RNA complementary to the Shine-Dalgarno sequence/5' UTR.
p.6
Structure and Organisation of Eukaryotic Genome
What is a kinetochore?
A complex of proteins that forms at each centromere and serves as the attachment point for spindle fibers.
p.5
Non-Coding DNA Functions in Eukaryotes
What are introns?
Sections of non-coding DNA within eukaryotic genes.
p.13
Comparison of Gene Regulation in Prokaryotes and Eukaryotes
How does control at the chromatin level differ between prokaryotes and eukaryotes?
Prokaryotes do not package DNA as chromatin and do not have histone modifications, while eukaryotes use chromatin remodeling involving histone acetylation and DNA methylation.
p.11
Chromatin Structure and Modification
What is the role of histone deacetylases?
They catalyze histone deacetylation, reverting histones to a positively charged state.
p.1
Non-Coding DNA Functions in Eukaryotes
What is the function of non-coding DNA in eukaryotes?
Non-coding DNA includes portions that do not encode protein or RNA, such as introns, centromeres, telomeres, promoters, enhancers, and silencers.
p.1
Gene Regulation Mechanisms
How can gene expression in eukaryotes be regulated?
At different levels including chromatin level, transcriptional level, and post-transcriptional level.
p.4
Chromatin Structure and Modification
What is a characteristic of heterochromatin?
It appears as darkly-stained regions.
p.3
Chromatin Structure and Modification
What role does Histone H1 play in nucleosomes?
It binds to the site where DNA enters and exits the nucleosome, stabilizing it.
p.16
Transcriptional Control of Gene Expression
What largely determines the precise control of transcription in eukaryotes?
The binding of specific transcription factors to DNA control elements.
p.12
Gene Regulation Mechanisms
How does DNA methylation block transcription factor binding?
By methylating CpG-rich sites where many transcription factors bind, preventing their attachment.
p.5
Transcriptional Control of Gene Expression
What is a silencer?
A specific nucleotide sequence that suppresses transcription by binding to repressor proteins.
p.4
Chromatin Structure and Modification
What is the function of euchromatin?
Contains genes that are actively transcribed or destined to be transcribed.
p.2
Post-Transcriptional Control of Gene Expression
What is alternative splicing?
A regulation mechanism that allows different combinations of exons to be joined, producing multiple protein variants from a single gene.
p.9
Gene Regulation Mechanisms
What are housekeeping genes?
Genes that are continuously expressed and involved in general cell maintenance and activity.
p.4
Chromatin Structure and Modification
Where is heterochromatin concentrated in chromosomes?
In specific regions, including centromeres and telomeres.
p.4
Chromatin Structure and Modification
How does the degree of condensation of chromatin get controlled?
Through chemical modification of DNA and histone proteins, such as methylation.
p.12
Gene Regulation Mechanisms
What is DNA methylation?
A modification of DNA structure through the addition of methyl groups, catalyzed by DNA methyltransferase, without altering the DNA sequence.
p.6
Structure and Organisation of Eukaryotic Genome
What chromosomal state does aneuploidy represent?
A state where the number of chromosomes is not a multiple of the haploid set.
p.11
Transcriptional Control of Gene Expression
How does histone acetylation affect transcription factors and RNA polymerase?
It allows greater accessibility to the underlying DNA sequence.
p.13
Transcriptional Control of Gene Expression
What is the effect of histone acetylation on transcription?
It generally enhances transcription by making DNA more accessible.
p.13
Transcriptional Control of Gene Expression
Is histone acetylation sufficient for transcriptional activation alone?
No, it often requires additional factors for a sufficient effect.
p.16
Transcriptional Control of Gene Expression
What activators are present in lens cells for gene expression?
Activators needed for the expression of the crystallin gene.
p.21
Post-Translational Control of Gene Expression
What is the purpose of protein degradation in cells?
To remove proteins that are no longer required and recycle raw materials like amino acids.
p.21
Post-Translational Control of Gene Expression
How are proteins degraded in eukaryotes?
Through ubiquitinylation and proteasome action.
p.9
Gene Regulation Mechanisms
What are the five main methods to control gene expression in eukaryotes?
Chromatin remodeling, transcription, post-transcription, translation, and post-translation.
p.2
Structure and Organisation of Eukaryotic Genome
What percentage of the eukaryotic genome codes for proteins or RNA?
More than 90% does not code for protein or RNA.
p.21
Post-Translational Control of Gene Expression
What mechanisms control the amount of proteins in eukaryotes?
Ubiquitinylation and protein degradation by the proteasome.
p.19
Translational Control of Gene Expression
How do translational repressors affect translation initiation in eukaryotes?
They bind to the 5' UTR of mRNA, preventing ribosome binding and formation of the translational initiation complex.
p.6
Structure and Organisation of Eukaryotic Genome
What is the primary function of centromeres?
Sister chromatid adhesion and kinetochore formation.
p.12
Gene Regulation Mechanisms
Where is DNA methylation mostly observed?
In transcriptionally inactive regions of the genome.
p.3
Chromatin Structure and Modification
What do chromatin fibres associate with to form looped domains?
Central nuclear matrix scaffold proteins.
p.4
Chromatin Structure and Modification
What are the two types of chromatin distinguished in eukaryotic cells?
Euchromatin and heterochromatin.
p.14
Transcriptional Control of Gene Expression
What is required for eukaryotic transcription?
A variety of transcription factors that bind to specific control elements in the genome.
p.10
Chromatin Structure and Modification
What prevents the binding of general transcription factors and RNA polymerase to the promoter?
The close packing of DNA around histones in nucleosomes.
p.1
Transcriptional Control of Gene Expression
What are control elements in transcriptional control of gene expression?
Promoters, silencers, and enhancers.
p.4
Chromatin Structure and Modification
What happens to genes packaged into heterochromatin?
They are usually transcriptionally inactive.
p.4
Chromatin Structure and Modification
What is X-chromosome inactivation?
A process where one of the two X chromosomes in female mammals remains as heterochromatin.
p.2
Chromatin Structure and Modification
What is a nucleosome?
A 'bead-like' structure formed by DNA winding around a core of histone proteins.
p.19
Translational Control of Gene Expression
What can regulate the half-life of mRNA?
Certain hormones and specific proteins that bind to the 3' UTR of mRNA can stimulate or retard degradation.
p.19
Translational Control of Gene Expression
What mechanism do prokaryotes use to prolong the half-life of mRNA?
Formation of a stem-loop at the 3' end, which prevents digestion by 3' exonucleases.
p.17
Gene Regulation Mechanisms
What is the role of enhancers and silencers in eukaryotic transcriptional control?
They may increase or decrease the rate of transcription of the target gene.
p.6
Structure and Organisation of Eukaryotic Genome
What can aberrant centromeric function lead to?
Improper chromosomal alignment and segregation, resulting in aneuploidy.
p.3
Chromatin Structure and Modification
What is the 30-nm chromatin fibre?
The helical structure formed by the coiling of nucleosome 'beads'.
p.9
Gene Regulation Mechanisms
How do prokaryotes utilize gene regulation?
They take advantage of changing environmental conditions, such as food sources, to respond efficiently and economically.
p.20
Post-Translational Control of Gene Expression
What is glycosylation?
The addition of short carbohydrate chains to proteins, forming glycoproteins.
p.21
Post-Translational Control of Gene Expression
What role does ubiquitin play in protein degradation?
Ubiquitin is covalently added to the N-terminus of the protein to mark it for degradation.
p.20
Post-Translational Control of Gene Expression
What is the function of methylation in protein regulation?
It activates enzymes like phosphatase that remove phosphate groups from proteins.
p.21
Post-Translational Control of Gene Expression
Do prokaryotes perform post-translational modifications?
No, post-translational modifications do not occur in prokaryotes.
p.14
Transcriptional Control of Gene Expression
What effect do activators have on RNA polymerase activity?
They upregulate the activity of RNA polymerase.
p.14
Transcriptional Control of Gene Expression
What are the potential effects of transcription regulation?
Increased or decreased rate of transcription.
p.13
Chromatin Structure and Modification
What is DNA methylation?
A modification that involves the addition of methyl groups to DNA, influencing gene expression.
p.18
Comparison of Gene Regulation in Prokaryotes and Eukaryotes
Do post-transcriptional modifications occur in prokaryotes?
No, they do not occur in prokaryotes.
p.9
Gene Regulation Mechanisms
Why is control of gene expression essential for all organisms?
It allows organisms to respond efficiently to changing environmental conditions and maintain homeostasis.
p.12
Gene Regulation Mechanisms
What is the result of histone deacetylation induced by DNA methylation?
Remodeling of chromatin to be more closely packed, leading to transcriptionally inactive regions.
p.2
Post-Transcriptional Control of Gene Expression
What is the role of post-transcriptional control in eukaryotic gene expression?
It regulates gene expression at the processing of pre-mRNA, including splicing, polyadenylation, and 5' capping.
p.20
Post-Translational Control of Gene Expression
How does phosphorylation affect proteins?
It activates many transcription factors and proteins involved in cell signaling.
p.9
Gene Regulation Mechanisms
At what level is gene expression primarily controlled in prokaryotes?
At the transcriptional level, often using the operon system.
p.4
Chromatin Structure and Modification
What effect does modification of histone proteins have during the cell cycle?
It changes their charge, affecting the association between DNA and histone proteins.
p.17
Gene Regulation Mechanisms
How does transcriptional control in eukaryotes differ from prokaryotes?
Eukaryotes involve a unique combination of control elements, including enhancers and silencers that are distal to the genes.
p.15
Gene Regulation Mechanisms
What is the function of the DNA binding domain in transcription factors?
For recognition and binding to a specific DNA sequence.
p.15
Gene Regulation Mechanisms
What is one way eukaryotic repressors affect general transcription factors?
They can interact directly to block further assembly or prevent the release of RNA polymerase.
p.13
Chromatin Structure and Modification
What is histone acetylation?
A modification that involves the addition of acetyl groups to histone proteins, affecting gene expression.
p.18
Comparison of Gene Regulation in Prokaryotes and Eukaryotes
How do prokaryotes differ from eukaryotes in post-transcriptional control?
In prokaryotes, transcription and translation occur simultaneously, while in eukaryotes, they are separated by the nuclear envelope.
p.5
Transcriptional Control of Gene Expression
What is the function of an enhancer?
It activates transcription by binding to activator proteins, located far from the transcription start site.
p.11
Transcriptional Control of Gene Expression
What is the consequence of histone deacetylation on gene expression?
It switches off gene expression due to lower accessibility of proteins to DNA.
p.11
Transcriptional Control of Gene Expression
What is the relationship between histone acetylation and transcriptionally active regions?
Transcriptionally active regions usually contain acetylated histones.
p.8
Role of Introns and Alternative Splicing
What is the end replication problem?
It causes telomeres to shorten during DNA replication in eukaryotes.
p.10
Chromatin Structure and Modification
What is histone acetylation?
A post-translational modification that can affect DNA packaging and transcription.
p.8
Role of Introns and Alternative Splicing
What sequence do human telomeres contain?
5′ - TTAGGG - 3′ repeats.
p.21
Post-Translational Control of Gene Expression
How can protein activity be controlled in prokaryotes?
Through biochemical modifications and proteolytic cleavage.
p.17
Gene Regulation Mechanisms
What is a key feature of transcriptional control in prokaryotes?
Involves a single operator that is proximal to the genes under its control.
p.17
Gene Regulation Mechanisms
What type of mRNA is produced in eukaryotes?
Monocistronic mRNA, where each gene is controlled by its own promoter.
p.15
Gene Regulation Mechanisms
How do eukaryotic repressor proteins differ from prokaryotic ones?
Eukaryotic repressors have many more mechanisms of action and do not directly block RNA polymerase binding.
p.6
Structure and Organisation of Eukaryotic Genome
What is aneuploidy?
A condition where the number of chromosomes is abnormal due to extra or missing chromosomes.
p.16
Transcriptional Control of Gene Expression
What is required for a combination of control elements to activate or repress transcription?
The appropriate activator or repressor proteins must be present at a precise time or in a specific cell type.
p.4
Chromatin Structure and Modification
How does euchromatin appear under a light microscope?
As lightly-stained regions.
p.8
Role of Introns and Alternative Splicing
What happens to cells after a limited number of divisions due to telomere length?
They undergo apoptosis (programmed cell death).
p.1
Chromatin Structure and Modification
What are the two main mechanisms of gene regulation at the chromatin level?
Histone modification and DNA methylation.
p.1
Transcriptional Control of Gene Expression
What role do transcription factors play in gene regulation?
They include proteins such as activators and repressors that regulate gene expression.
p.19
Translational Control of Gene Expression
How do eukaryotes primarily control the amount of specific proteins in the cell?
By regulating the rate of transcription to control the amount of mRNA produced.
p.10
Chromatin Structure and Modification
What is the effect of histone modifications on transcription?
They can increase or decrease transcription by affecting DNA packaging.
p.2
Post-Translational Control of Gene Expression
What is the significance of histone modification in gene expression?
It plays a crucial role in regulating access to DNA and thus influences gene expression.
p.7
Non-Coding DNA Functions in Eukaryotes
What is one of the primary functions of telomeres?
To protect genes from being eroded via successive rounds of replication.
p.15
Gene Regulation Mechanisms
What is the role of the activation domain in transcription factors?
For interaction with other proteins of the transcriptional machinery.
p.5
Structure and Organisation of Eukaryotic Genome
What is the structure of a mitotic chromosome?
It consists of two identical sister chromatids joined at the centromeres.
p.16
Gene Regulation Mechanisms
What is combinational control in gene regulation?
It refers to the regulation of a gene by multiple enhancers or silencers, each active at different times or in different cell types.
p.1
Structure and Organisation of Eukaryotic Genome
What are the main components of the eukaryotic genome structure?
DNA/RNA, single/double-stranded, number of nucleotides, packing of DNA, linearity/circularity, and presence/absence of introns.
p.10
Chromatin Structure and Modification
How does chromatin packaging affect transcription in eukaryotes?
It can regulate transcription through chromatin remodeling.
p.20
Post-Translational Control of Gene Expression
What role does acetylation play in protein function?
It is essential for the activation of proteins like p53 and stabilizing microtubules.
p.14
Transcriptional Control of Gene Expression
What initiates the transcription initiation complex?
General transcription factors recognize and bind to the promoter via the TATA box and recruit RNA polymerase.
p.19
Translational Control of Gene Expression
What role does the 5' cap play in mRNA stability?
It shields the mRNA against degradation by 5' exonucleases, increasing its half-life.
p.7
Structure and Organisation of Eukaryotic Genome
What are telomeres?
Specialised DNA sequences that form the ends of linear DNA of eukaryotic chromosomes.
p.15
Gene Regulation Mechanisms
What are the two independent domains of transcription factors?
DNA binding domain and activation domain.
p.7
Non-Coding DNA Functions in Eukaryotes
What role do telomeres play in relation to DNA repair machinery?
They prevent the machinery from recognizing and sticking together the ends of chromosomes when there are breaks.
p.18
Role of Introns and Alternative Splicing
How does alternative splicing affect protein production?
It allows a single gene to code for more than one protein by including or excluding particular exons.
p.5
Role of Introns and Alternative Splicing
How do introns contribute to gene expression?
They allow for alternative splicing, enabling one gene to code for more than one polypeptide.
p.13
Comparison of Gene Regulation in Prokaryotes and Eukaryotes
What is the purpose of DNA methylation in prokaryotes?
To distinguish its genome from viral genomes as part of a protection mechanism against viral infection.
p.16
Gene Regulation Mechanisms
In the case study, why do liver cells and lens cells express different proteins despite having the same genes?
The types of activator and repressor proteins expressed in each cell type determine which genes are expressed.
p.16
Transcriptional Control of Gene Expression
What activators are present in liver cells for gene expression?
Activators needed for the expression of the albumin gene.
p.9
Gene Regulation Mechanisms
Do eukaryotic organisms express all their genes at all times?
No, they do not need to express all genes all the time or in all cells.
p.14
Transcriptional Control of Gene Expression
Where is the promoter located?
Proximal to the gene it regulates.
p.1
Comparison of Gene Regulation in Prokaryotes and Eukaryotes
What is the difference between eukaryotic and prokaryotic repressor proteins?
Eukaryotic repressor proteins have more complex interactions and regulatory mechanisms compared to prokaryotic ones.
p.10
Chromatin Structure and Modification
When does chromatin remodeling typically occur?
During cell differentiation.
p.20
Post-Translational Control of Gene Expression
Why do some polypeptides undergo proteolytic cleavage?
To fold into functional proteins.
p.20
Post-Translational Control of Gene Expression
How many amino acids does the active insulin molecule consist of?
51 amino acids, which is less than half of the original translation product.
p.7
Non-Coding DNA Functions in Eukaryotes
How do telomeres affect the lifespan of cells?
They limit the lifespan of cells.
p.17
Gene Regulation Mechanisms
What types of regulation can occur in prokaryotic transcriptional control?
Both positive regulation (via catabolite activator protein) and negative regulation (via repressor).
p.18
Role of Introns and Alternative Splicing
What is alternative splicing?
A regulated process that produces different mature mRNA sequences from the same pre-mRNA coded by the same gene.
p.11
Chromatin Structure and Modification
What is the effect of histone acetylation on the affinity between histones and DNA?
It lowers the affinity due to decreased positive charge.
p.16
Gene Regulation Mechanisms
How do unique combinations of control elements affect transcription regulation?
They have a more significant effect than the presence of a single unique control element.
p.9
Gene Regulation Mechanisms
What role does gene regulation play in multi-cellular eukaryotes?
It directs the development of the organism and maintains homeostasis.
p.14
Transcriptional Control of Gene Expression
What are the three main types of control elements?
Promoter, Enhancer, Silencer.
p.9
Gene Regulation Mechanisms
How does gene expression vary in multi-cellular organisms?
Different cell types express different genes to make different proteins, serving specialized functions.
p.21
Post-Translational Control of Gene Expression
What is the function of the proteasome?
It is a protease complex that degrades proteins marked by ubiquitin.
p.19
Translational Control of Gene Expression
What is the effect of a longer half-life of mRNA?
It allows the mRNA to remain in the cytoplasm longer and serve as a template for more protein translation.
p.20
Post-Translational Control of Gene Expression
What is the process of insulin maturation?
Involves removal of the signal peptide and C-chain, forming active insulin from pre-proinsulin.
p.7
Structure and Organisation of Eukaryotic Genome
What is the DNA sequence repeat found in human telomeres?
5’ - TTAGGG - 3’ repeated 100 - 1000 times.
p.7
Non-Coding DNA Functions in Eukaryotes
What problem do telomeres help to postpone?
The end-replication problem, which causes DNA to shorten after each replication.
p.15
Gene Regulation Mechanisms
How can eukaryotic repressors interact with activator proteins?
By binding to and masking the activation domain of an activator protein.
p.16
Gene Regulation Mechanisms
What role do repressor proteins play in different cell types?
They suppress the expression of particular genes, such as the albumin gene in lens cells.
p.10
Chromatin Structure and Modification
What factors control the dynamic arrangement of nucleosomes?
Post-translational modifications of histones and modifications of DNA residues.
p.2
Structure and Organisation of Eukaryotic Genome
What is the structure of the eukaryotic genome?
It consists of two or more linear chromosomes bound by the nuclear membrane, each containing a double-stranded DNA molecule associated with histones.
p.14
Transcriptional Control of Gene Expression
What mechanism is triggered by activators and repressors?
A DNA looping mechanism aided by DNA bending proteins.
p.8
Role of Introns and Alternative Splicing
What does DNA polymerase do after telomere extension?
It makes the extended portion of the telomere double stranded.
p.17
Gene Regulation Mechanisms
What type of mRNA is produced in prokaryotes?
Polycistronic mRNA, where multiple structural genes are controlled by the same promoter.
p.17
Post-Transcriptional Control of Gene Expression
What happens to mature mRNA in eukaryotes after processing?
It leaves the nucleus to be translated in the cytoplasm.
p.14
Transcriptional Control of Gene Expression
What effect do repressors have on RNA polymerase activity?
They downregulate the activity of RNA polymerase.
p.19
Translational Control of Gene Expression
What is a key difference in mRNA stability between prokaryotes and eukaryotes?
Eukaryotic mRNA has a 5' cap and a 3' poly-A tail, increasing its half-life, while prokaryotic mRNA is typically less stable.
p.7
Structure and Organisation of Eukaryotic Genome
What happens to broken chromosomes that lack telomeres?
They are recognized as defective by cellular DNA repair machinery.
p.17
Post-Transcriptional Control of Gene Expression
What are the post-transcriptional modifications that pre-mRNA undergoes in eukaryotes?
5’ capping, splicing, and 3’ polyadenylation.
p.15
Gene Regulation Mechanisms
What is heterochromatin and how is it related to eukaryotic repressors?
Heterochromatin is a tightly packed form of DNA that is resistant to transcription, and eukaryotic repressors can package chromatin into this form.
p.15
Gene Regulation Mechanisms
What is one mechanism by which eukaryotic repressors can block transcription?
Block the binding of an activator protein to the enhancer sequence.
p.15
Gene Regulation Mechanisms
How do eukaryotic repressors modify histones?
By recruiting histone deacetylases to condense the chromatin at the promoter region, making it less accessible.
