Trp Operon and DNA Modification

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Questions and Answers

What role does tryptophan (Trp) play in regulating gene expression?

It binds to the operator region inhibiting RNA polymerase.

It detaches the ribosome from mRNA to promote protein synthesis.

It binds to the leader sequence regulating the amount produced by the cell. (correct)

It forms a terminator hairpin loop activating genes.

What happens when both repression and attenuation occur due to high levels of Trp?

mRNA is produced at an increased rate.

No Trp is produced, allowing the ribosome to remain attached.

Only the repressor protein binds to the operator.

Both gene expression is blocked and resources are conserved. (correct)

What is the outcome of using restriction enzymes on DNA?

They produce only blunt ends irrespective of the DNA sequence.

They allow for the repair of sugar-phosphate bonds in DNA.

They facilitate the amplification of DNA segments.

They cut phosphodiester bonds creating sticky or blunt ends. (correct)

What is the primary function of DNA polymerase in the context of DNA modification?

It constructs DNA strands from nucleotides. Signup and view all the answers

In gel electrophoresis, what determines the distance DNA samples travel?

The size of the DNA fragments, with smaller fragments traveling further. Signup and view all the answers

What is one benefit of using CRISPR technology on crops?

It can enhance photosynthetic efficiency. Signup and view all the answers

Which fermentation process occurs in animals during anaerobic respiration?

Lactic acid formation Signup and view all the answers

Which enzyme's affinity to CO2 can be improved using CRISPR technology?

Rubisco Signup and view all the answers

What is the primary role of oxygen in cellular respiration?

Acts as the final electron acceptor Signup and view all the answers

How many ATP are produced through glycolysis?

Net 2 ATP Signup and view all the answers

What is the first step in both aerobic and anaerobic respiration?

Glycolysis Signup and view all the answers

Where does the Krebs Cycle occur within the cell?

Matrix of mitochondria Signup and view all the answers

In the biofuel production process, what is the role of yeast?

To undergo anaerobic fermentation and produce bioethanol Signup and view all the answers

What inputs are required for the Electron Transport Chain?

FADH2, NADH, and Oxygen Signup and view all the answers

Which type of cell is primarily responsible for phagocytosis of pathogens?

Antigen presenting cells Signup and view all the answers

Which stage of cellular respiration generates the most ATP?

Electron Transport Chain Signup and view all the answers

Which coenzymes travel to the Electron Transport Chain from glycolysis and the Krebs Cycle?

NADH and FADH2 Signup and view all the answers

How does increasing glucose concentration affect cellular respiration?

It similarly increases respiration rates as increasing oxygen concentration Signup and view all the answers

What is one of the key functions of natural killer cells in the immune response?

Destruction of body cells with defective MHC1 Signup and view all the answers

Which of the following statements about CRISPR and crop yields is true?

It can accelerate the maturity time of crops. Signup and view all the answers

Which type of cells migrate to the lymph nodes to activate T-helper cells?

Dendritic cells Signup and view all the answers

What is the primary effect of genetic drift on allele frequencies in populations?

Randomly alters allele frequencies Signup and view all the answers

Which example illustrates natural selection in bacteria?

Resistance developing after exposure to antibiotics Signup and view all the answers

What does the founder effect lead to in newly established populations?

Loss of alleles present in the original population Signup and view all the answers

How does natural selection contribute to speciation?

By promoting adaptation to various environments Signup and view all the answers

What leads to the ineffectiveness of vaccines over time?

Minor genetic changes that accumulate gradually Signup and view all the answers

What role do cytokines play in the inflammatory response?

They stimulate the movement of immune cells to the damaged site. Signup and view all the answers

What causes the site of damage to become hot, swollen, and red during inflammation?

Increased cellular activity and vascular changes. Signup and view all the answers

How does the adaptive immune response provide long-term immunity?

Through the generation of memory cells. Signup and view all the answers

What initiates the activation of the T-helper cell in the adaptive immune response?

Antigen presentation by antigen-presenting cells (APCs). Signup and view all the answers

What is the main function of plasma B cells during the adaptive immune response?

To produce specific antibodies. Signup and view all the answers

Which part of the immune response is responsible for directly attacking infected cells?

Cytotoxic T-cells. Signup and view all the answers

What is the primary function of the physical barriers in plant immunity?

To prevent pathogen access Signup and view all the answers

Which of the following is NOT considered a chemical barrier in plant immunity?

Waxy cuticle Signup and view all the answers

Study Notes

Trp Operon

Trp binds to the repressor protein
The Trp-repressor protein complex binds to the operator region
RNA polymerase cannot produce genes E-A
When the Trp levels are high, the repressor protein binds to the operator region
The repressor protein blocks RNA polymerase from transcribing the genes
When Trp levels are low, the repressor protein detaches from the operator region
RNA polymerase can transcribe the genes E-A
The Trp operon regulates the amount of Trp produced by the cell
Attenuation is another mechanism for regulating Trp production
When Trp levels are high, both repression and attenuation can occur
The ribosome is detached from the attenuated mRNA
No Trp is produced
The cell conserves energy and resources

DNA Modification

Restriction enzymes cut phosphodiester bonds in DNA
Sticky ends allow for easier insertion of the target gene in the correct orientation
Blunt ends have no overhang
Ligase repairs broken phosphodiester bonds in DNA
Polymerases build DNA (eg Taq polymerase) and RNA
DNA polymerase is used in PCR

Gel Electrophoresis

DNA samples are cut with restriction enzymes to expose STR sites
DNA samples are loaded into wells
Electronic current is used to separate samples from largest (travel least distance) to smallest (travel the furthest distance)
Samples with the largest molecular weight travel the shortest distance
Samples with the smallest molecular weight travel the furthest distance

CRISPR and Crops

CRISPR technology can be used to modify crops
CRISPR can modify crops to improve photosynthetic efficiency
CRISPR can improve rubisco's affinity to CO2
CRISPR can improve chlorophyll's ability to capture all wavelengths of light
CRISPR can improve the speed of reactions in photosynthesis
CRISPR can also be used to modify crops to improve their crop yields
CRISPR can increase the number of harvests per stem and accelerate the time it takes for the crop to mature

Cellular Respiration

Cellular respiration uses glucose (organic energy) to produce ATP from ADP+Pi
Respiration can be aerobic (requires oxygen) and anaerobic (no oxygen)

Stages of Aerobic Respiration

Glycolysis
- Inputs: Glucose, NAD+
- Outputs: 2x Pyruvate, NADH
- Location: Cytoplasm
- Net: 2 ATP produced
Krebs Cycle
- Inputs: 2x Acetyl CoA, NAD+, FAD+
- Outputs: CO2, NADH, FADH2
- Location: Matrix of mitochondria
- Net: 2 ATP produced
Electron Transport Chain
- Inputs: FADH2, NADH, ADP+Pi, Oxygen
- Outputs: NAD+, FAD+, ATP, Water
- Location: Cristae of Mitochondria
- Net: 26-28 ATP produced
Glycolysis is always the first step in both aerobic and anaerobic respiration
The link reaction occurs when pyruvate enters the mitochondria and is converted into acetyl CoA
NADH and FADH2 from glycolysis and Krebs travel to the ETC, creating a proton gradient
Protons pass through ATP synthase, producing ATP from ADP+Pi
Oxygen is the final electron acceptor

Anaerobic Respiration

Anaerobic respiration occurs in all living things
It is always the first step in respiration (Glycolysis)
Lactic acid formation occurs in animals
Alcoholic fermentation occurs in yeast and plants
Glycolysis produces the 2 ATP in anaerobic respiration

Factors Affecting Cellular Respiration

Increasing glucose and oxygen concentration will cause the same graph
Increasing temperature will increase rate of reaction to a point where enzymes denature
Increasing pH can have an effect on enzymes

Biofuel

Biofuel is sustainable
Biofuel is made through anaerobic fermentation
Biofuel is made from organic plant waste
Organic plant waste is broken down into glucose
Glucose is supplied to yeast in fermentation chambers
Yeast use glucose to undergo anaerobic fermentation
Bioethanol is harvested and purified for commercial use

Innate Immunity

Macrophages
- APC - phagocytosis of pathogen and displays foreign antigen as MHCII
Dendritic Cells
- APC - phagocytosis of pathogen and displays foreign antigen as MHCII
Neutrophils
- APC - phagocytosis of pathogen and displays foreign antigen as MHCII
Eosinophils
- Responsible for parasite infections
Natural Killer Cells
- Attack body cells with defective MHC1 via the release of perforins
Mast Cells
- Inflammation & histamine release
- Allergic responses & histamine release

Antigen Presentation

Antigen presenting cells (APCs)
- Macrophages
- Dendritic cells
- Neutrophils
APCs migrate to the lymph node and activate T-helper cells
Cytokines are released from damaged tissue
Immune cells move to the site of damage
Mast cells release histamine
Histamine causes:
- Leaky capillaries
- Vasodilation
Site becomes hot, swollen, and red due to increased cellular activity
Macrophages remove debris

Adaptive Immune Response

Adaptive immune response provides long-term immunity to pathogens and protects against reinfection through the production of memory cells.
The adaptive immune response is coordinated by the T-helper cell after antigen presentation
Humoral (B Cell) Response
- T-helper cell is activated by APC
- T-helper cell releases cytokines and activates naïve B-cell
- Naïve B-cell undergoes clonal selection to produce plasma B-cell and memory B-cell
- Plasma B-cell produces specific antibodies that bind to and neutralize foreign antigen
- Memory B-cell remains in the bloodstream and provides long-term immunity against subsequent infections
Cell-mediated (T Cell) Response
- T-helper cell is activated by APC
- T-helper cell releases cytokines and activates naïve T-cell
- Naïve T-cell undergoes clonal selection to produce specific cytotoxic T-cells
- Cytotoxic T-cells attack cells with specific defective MHC1, causing apoptosis or releasing perforins
- Memory T-cells provide long-term immunity

Plant Immunity

Plants have no adaptive immune responses
Physical Barriers
- Thorns
- Trichomes (hairs)
- Waxy cuticle
- Lignin walls
Chemical Barriers
- Enzymes
- Essential Oils
- Phytoalexins
- Defensins

Preventing the Spread of Pathogens

Identify the pathogen
Identify its transmission
Develop a vaccine
Monoclonal antibodies are given as treatment
Direct contact can also spread pathogens

Genetic Drift

Genetic drift is a random change event that can cause changes in allele frequencies in populations.
Genetic drift is not an example of natural selection.

Bottleneck Effect

Chance event where randomly some members of the population survive a natural disaster and others do not
Affects smaller populations more than bigger populations.
Can result in the loss of alleles from the population
Decreases variation in the population

Founder Effect

Small number of members branch off to form a brand new population.
Only the alleles present in the founding individuals will be present in the new population
Causes a decrease in variation
Decreases variation in the population

Natural Selection

Natural selection is the driving force for evolution.
Variation in a population allows for traits to be selected for (fit) or selected against (unfit).
Over time, the allele frequency changes depending on the organism's environment
Natural selection can lead to speciation.
Natural selection reduces genetic variation in a population

Natural Selection Example: Bacterial Resistance

VARIATION: In a population of bacteria, some have resistance to antibiotics, others do not.
SELECTION PRESSURE: Exposure to antibiotics; only those with resistance survive and reproduce (no resistance = no survival).
FUTURE GENERATIONS: Higher allele frequency of resistant bacteria.
NATURAL SELECTION OCCURED.

Antigenic Shift and Drift

Vaccines become ineffective due to random mutations in the virus over time.
This can be gradual and minimal changes or can be abrupt.

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Description

This quiz covers key concepts of the Trp operon and DNA modification techniques such as restriction enzymes and ligase functions. Understand the mechanisms of gene regulation through the Trp operon and the importance of DNA modification in genetic engineering. Test your knowledge on these essential molecular biology topics.