Answer: The answer is that have to bind to receptors to cross the membrane.
Explanation:
A hydrophilic substance can easily dissolve or absorbed in a water containing vessel, not a fat or lipid vessel like biological membranes.
Now, protein-based hormones like dopamine or serotonin ARE NOT LIPID-SOLUBLE; so, have to bind to receptors positioned in the membrane and MAY also require energy in form of ATP for across the membrane before they would exert their function on the target cell or organelles.
Which of the following is NOT an exotic species that has caused unforeseen ecological disruption where it has been introduced, whether accidentally or deliberately?
Answer:
All of the above have caused ecological disruption
Explanation:
Ecological disruption can be described as a kind of disturbance, whether of biological or non-biological origin which affects the pattern of a particular ecosystem. Disruptions might be caused due to factors such as weather changes or biotic factors such as the invasion of a predator species which disrupts the whole food web of an ecosystem. Any new species, when introduced in a stable ecosystem, will cause disruption in some way or the other.
Which specialty area would be most interested in identifying the brain-activation patterns associated with a person's perception of different objects?
Answer: Coherence analysis
Explanation: Coherence analysis indicates the brain activation pattern and and shows similarity of frequency information between areas in the brain.
NEED HELP ASAP I DONT HAVE MUCH TIME
How are the sun, Earth, and the moon aligned during a solar eclipse?
In a straight line with the moon between Earth and the sun
In a straight line with Earth between the sun and the moon
With the sun and the moon at right angles to each other in relation to Earth
With the sun and Earth at right angles to each other in relation to the moon
Answer:
i believe it is the strait line moon between the earth and the sun
Explanation:
this is because a solar eclipse is when the moon blocks out the sun.
hope this helped
Answer:
A solar eclipse occurs when the moon gets between Earth and the sun, and the moon casts a shadow over Earth. A solar eclipse can only take place at the phase of new moon, when the moon passes directly between the sun and Earth and its shadows fall upon Earth's surface.
Explanation:
So basically In a straight line with the moon between Earth and the sun
The DNA in a bacterial (prokaryotic) chromosome is best described as:
A) a single circular double-helical molecule.
B) a single linear double-helical molecule.
C) a single linear single-stranded molecule.
D) multiple linear double-helical molecules.
E) multiple linear single-stranded molecules.
Answer: A
Explanation:
Unlike the linear, double stranded, helical, supercoiled Eukaryotic chromosome, the prokaryotic bacterial chromosome is circular, single molecule of double stranded, helical, supercoiled DNA.
The bacteria DNA is said to be circular because the two ends of the double-stranded DNA are covalently bond together to form both a physical and genetic circle.
Plasmid another genetic material in bacterial are circular, double stranded DNA molecules that replicate independently if the bacteria DNA.
If you were designing this experiment for a fertilizer manufacturer, what changes would you make in the experimental design to be confident that your results would be accepted as fact by the scientific community? Explain your answer
Answer:
You have not stated the experiment that is being done here.
I want to believe it is The experimental design and fertilizer applications for organic manures
Explanation:
You need to test some plants in the experiment more than once. This test needs to be carried out on different plants so as to confirm its importance.
Some factors needs to be considered like the different types of fertilizers available and these need to be tested.
Change the abiotic and biotic factors to determine productivity.
Margination refers to Margination refers to dilation of blood vessels. the movement of phagocytes through walls of blood vessels. the chemotactic response of phagocytes. adherence of phagocytes to the lining of blood vessels.
Answer:
The correct answer is- adherence of phagocytes to the lining of blood vessels.
Explanation:
The proper functioning of phagocytes or white blood cells is not possible without the adherence ability of these cells to the vascular epithelium. So to facilitate the adhesion the phagocytes migrate towards the site through blood.
Margination is the adherence and accumulation of phagocytes on the blood vessel lining present at the injury site. It is a part of inflammatory response. The margination depends on various conditions like flow rate, red blood cell aggregation, local hematocrit, etc. Therefore the correct answer is-adherence of phagocytes to the lining of blood vessels.
Answer:
Adherence of phagocytes to the lining of blood vessels.
Explanation:
Margination is the process of the movement of the selected particles across the walls of the particular channels. The particles can easilu undergo margination in blood.
The margination is useful for the clearance of the blood from the pathogens and separation of the effected cells. The margination is also performed by the immune cells especially macrophages for for the phagocytic activity and adherence with the blood vessels lining.
Thus, the correct answer is option (4).
Toward the end of the last ice age, what power source was discovered that helped humans transition away from a nomadic lifestyle?
Answer:
Quaternary glaciation is the most recent ice age, starting from 3000 years ago and continuing until today, but several glacial and interglacial periods are recognized, currently living in the ice age in Antarctica, Greenland and the Arctic (Regions covered with ice), but it is also in interglacial limitations, due to the warm climates of the planet, it is also assumed that in conjunction with the ice age that was lived, phenomena that allowed advances in man with respect to its source of energy and its lifestyle that is explained with Prehistory.
In the Palaeolithic, the first human beings who inhabited a 7000 years ago feed on fish and other animals. These human beings moved from one place to another, so they were nomads, lived in caves, cabins and outdoors. It was then that 7 million years ago they discovered more profitable and evolved energy sources. Likewise, they already lived in villages and towns, these humans stopped being nomads and became sedentary in their lifestyles. They also managed to manufacture stone tools and vessels.
Answer the following questions.1. List and describe the anatomical components that make up a muscle fiber. 2. List the components of a motor unit. 3. What are the steps in excitation–contraction coupling? 4. What is the role of calcium in muscle contraction? 5. Describe the sliding filament theory. How do muscle fibers shorten? 6. What are the basic characteristics that differ between type I and type II muscle fibers? 7. What is the role of genetics in determining the proportions of muscle fiber types and the potential for success in selected activities? 8. Describe the relation between muscle force development and the recruitment of type I and type II motor units. 9. Explain, and give examples of, how concentric, static, and eccentric contractions differ. 10. What two mechanisms are used by the body to increase force production in a single muscle? 11. What is the optimal length of a muscle for maximal force development? 12. What is the relation between maximal force development and the speed of shortening (concentric) and lengthening (eccentric) contractions? 13. In muscle contraction, what roles are played by the protein titin? 14. Why do previously trained muscles adapt more quickly to retraining after a period of disuse?
The Calcium bind with actin and troponin is removed that was blocking. Now myosin can attach and start contracting.
What made the Muscular system?
The muscular system of a body is made up of muscles and muscles are made up of millions of muscle fibers.
A muscle fiber is made up of small units called sarcomere, which contains actin and myosin fibers.
A muscle contracts when action potential spread in the sarcomere space the calcium is released due to action potential.
Calcium bind with actin and troponin is removed that was blocking. Now myosin can attach and start contracting.
Therefore, the Calcium bind with actin and troponin is removed that was blocking. Now myosin can attach and start contracting.
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In a nursing class the instructor explains the vulnerability of the organ systems during formation, such as the respiratory and circulatory systems, to environmental influences. This process of organ formation is called ________
Answer:
organogenesis
Explanation:
Organogenesis is defined as a process in which the three germ layers differentiate further to form several organs.
The embryonic stem cell is responsible for determining the ultimate cell type. During this process, neural system is formed and several morphological changes occur. The neural system further differentiates and develops to form neural tube and ultimately converts into brain and spinal cord. While folds and dense clusters are formed in the embryo that later form organs.
Neuroglia do not conduct impulses; they protect the nervous system through phagocytosis by engulfing and digesting any unwanted substances.
A. True
B. False
Answer:
Answer is A. True.
Explanation:
The neuroglia are not neurons but are also found in the nervous system. And their functions include the support they render to the neurons, and maintain the equilibrium of the nervous system.
There are various examples of neuroglia, and they are found in both central nervous system and peripheral nervous system.
Those that are found in the central nervous system include,
1. Oligodendrocytes.....which provide structural frame work.
2. Microglia...they remove waste by phagocytosis.
3. Astrocytes.... they maintain blood brain barrier.
4. Ependymal.... help in the production of cerebrospinal fluid.
Those in the peripheral nervous system include
1. Satellite cells.....they regulate nutrients.
2. Schwann cells...they myelinate axons
When created an mRNA, a cell matched a T with a G. This led to a different amino acid being added during translation. When this happens, what is it called?
Answer:
Substitution error
Explanation:
This is a type of mutation that rarely happens, it does not effect the order its read in so its not a frameshift which could be a deletion or addition. So its substitution.
In the context of psychosomatic medicine, Flanders Dunbar and Franz Alexander maintained that conflicts produce anxiety, which becomes unconscious and takes a physiological toll on the body via the?
Answer:
Autonomic nervous system.
Explanation:
The human psychology involves the study of the emotions, anger and feelings of the humans with themselves and other people of the society. The emotions are controlled by the external as well as internal factors.
The peripheral nervous system of the body constitutes the autonomic nervous system. This system is activated during the stress and anxiety response. The autonomic nervous system prepares the body for the fight and flight mechanism.
Thus, the answer is autonomic nervous system.
Natural selection suggests that creatures with mutations disadvantageous to survival will not live to reproduce, yet there are examples, such as albino animals, found occasionally. Do these exceptions discredit natural selection? Explain your answer.
Answer:
No, these exceptions do not discredit natural selection.
Explanation:
Natural selection tends to favour those organisms which are better adapted to live in an environment. But it does not completely remove the other organisms from the world that are less adapted to live in an environment. Usually, the number of these organisms that are not favoured by natural selection is very less as compared to the number of organisms which are favoured by natural selection. As we see, the number of albino animals is far lesser as compared to their wild-type animals.
Answer: These types of exceptions do NOT discredit natural selection.
Explanation:
Natural selection is based on the odds that certain traits will not adapt well in certain environments and ecosystems. It recognizes that organisms with mutations may be disadvantageous or not since the mutation is non-specific. In instances such as albinoism, the mutation is more likely to be disadvantageous though in some environments (like the desert) it could be a benefit. Natural selection is not an exact science or absolute rule, it is based on probabilities and variations, so exceptions will always exist.
What action must a Marine take to accomplish the task of enabling themselves and their Marines to assume progressively greater responsibilities in the Marine Corps and society?
Marines must go through a process of resocialization to assume greater responsibilities in the Marine Corps and society.
Explanation:The action that a Marine must take to enable themselves and their Marines to assume progressively greater responsibilities in the Marine Corps and society is to go through a process of resocialization. This process involves learning discipline, a capacity for hard work, and setting aside personal goals for the greater good.
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To enable Marines to assume greater responsibilities, leaders must prioritize continuous learning, mentorship, challenging assignments, and instilling core values like honor and commitment.
To enable themselves and their Marines to assume progressively greater responsibilities in the Marine Corps and society, a Marine must prioritize several actions. Firstly, they should cultivate a culture of continuous learning and personal development within their unit, encouraging Marines to seek out opportunities for growth and education. This includes promoting formal education programs, professional military education, and civilian education options.
Additionally, effective mentorship is crucial. Marines should actively mentor and be mentored, passing on knowledge, skills, and leadership experience. By fostering a supportive environment where junior Marines feel empowered to voice their ideas and concerns, leaders can help them develop confidence and critical thinking skills necessary for assuming greater responsibilities.
Furthermore, leaders must provide challenging assignments and opportunities for leadership roles, allowing Marines to demonstrate their capabilities and hone their leadership skills. Encouraging a mindset of accountability and ownership of tasks fosters initiative and prepares Marines for higher-level responsibilities.
Lastly, emphasizing the Marine Corps' core values of honor, courage, and commitment instills a sense of duty and responsibility, both within the Corps and in society at large, preparing Marines to excel in leadership roles on and off the battlefield.
A 7-year-old boy presents complaining of occasional intermittent lower abdominal pain over the last several weeks associated with a decline in the frequency of bowel movements to one every third day. When he does defecate, stools are hard to pass and sometimes painful. There is no blood in the stools. He has no chronic medical problems, has never had surgery, and takes no medications. Review of systems are negative and physical exam is normal. What is the most appropriate initial intervention for this child?
Answer:
Polyethylene glycol.
Explanation:
The abdominal pain might occur in the area of the pelvic regions and the chest area. The lower abdominal pain is common in children that might occur due to the constipation.
The increase or the presence of the polyethylene glycol in the abdomen can cause pain. This affects the bowel movements, bloating, vomiting, diarrhea and in excess condition may also cause the rectal bleeding in the children as well as in adult.
Thus, the answer is polyethylene glycol.
A client visits an orthopedic specialist because of pain beginning in the low back and radiating behind the right thigh and down below the right knee. The doctor suspects a diagnosis of sciatica. The nurse knows that the origin of the pain is between which intervertebral disks?
ANSWER: The origin of the pain is from the intervertebral disks of the lumbosacral spine.
EXPLANATION:
Sciatica is pain in the lower extremity resulting from irritation of the sciatic nerve.
The sciatic nerve is the largest nerve in the body and begins from nerve roots in the lumbar spinal cord in the low back and extends through the buttock area to send nerve endings down the lower limb.
Sciatica is caused by irritation of the root(s) of the lower lumbar and lumbosacral spine. Additional common causes of sciatica include: Lumbar spinal stenosis (narrowing of the spinal canal in the lower back) Degenerative disc disease (breakdown of discs, which act as cushions between the vertebrae).
Answer:
L4, L5, and S1
Explanation:
The lower lumbar disks, L4–L5 and L5–S1, are subject to the greatest mechanical stress and the greatest degenerative changes. Disk protrusion (herniated nucleus pulposus) or facet joint changes can cause pressure on nerve roots as they leave the spinal canal, which results in pain that radiates along the nerve.
The town council wanted to beautify the streets by planting trees along the curbs in front of houses whose trees had died, Melinda refused to have new trees planted at her curb_________.
Answer:
The options
A. Comma splice
B. Fused sentence
The CORRECT ANSWER IS A.
A. Comma splice
Explanation:
In English grammar, a comma splice can also be called a comma fault.
It occurs when the comma is uesd to join two independent clauses or complete sentences with a comma and no conjunction.
This form of writing is often used in literary writing to portrait a certain mood of informality.
A comma splices can be corrected in three varying ways such as:
-using a coordinating conjunction (for, and, nor, but, or, yet, so) to come right after the comma.
-converting the comma to semicolon.
-converting the comma to a period
A slice of pizza has 500 kcal. If we could burn the pizza anduse all the heat to warm a 50-L container of cold water, what wouldbe the approximate increase in the temperature of the water?(Note: A liter of cold water weighs about 1 kg.)
a. 50°C
b. 5°C
c. 10°C
d. 100°C
e. 1°C
Answer:
c. 10°C
Explanation:
Given that: A slice of pizza has 500 kcal.
That is to say Q = 500kcal
If the pizza was burned and all the heat were used to warm a 50-L container of cold water,
what would be the approximate increase in the temperature of the water?
We were also being told to note that; A liter of cold water weighs about 1 kg.
i.e 50-L container weighs about 50kg (mass)
∴ Since;
Q= 500kcal,
m = 50kg; &
the specific heact (c) = 1
we can find the approximate increase in the temperature of the water by using the formula:
Q = mcΔT
ΔT = [tex]\frac{Q}{mc}[/tex]
ΔT = [tex]\frac{500}{50*1}[/tex]
ΔT = 10°C
How do prions disrupt the normal function of an organism and cause diseases such as mad cow disease?
Answer:
Prions causes abnormal folding of the prion proteins in the brain.
Explanation:
Prions are the abnormal infectious agents composed only of the proteins and no nucleic acids. The prions cause several neurodegenerative diseases in the humans as well as the mammals.
The prions cause the cow mad disease in the cows by affecting the brain of the cow as the prions act on the prion proteins present in the brain only and change their conformation. This leads to the degeneration of the neurons and causes tiny pores in the brain giving sponge-like appearance.
This slows down the mental activity and thus ultimately leads to the death of the cow.
Which of the following is not a result of hydrogen bonds?
A. Two hydrogen atoms join together to form a molecule of hydrogen gas.
B. An enzyme has a unique shape that allows it to bond only with specific molecules.
C. Two strands of DNA are linked together taking a shape similar to a ladder.
D.Some hair is straight, some wavy, and some very curly.
Answer:
Answer is A. Two hydrogen atoms join together to form a molecule of hydrogen gas.
Explanation:
The electromagnetic attraction existing between hydrogen and other electronegative atom, such as nitrogen or oxygen, is known as hydrogen bond. It can also be explained as the electromagnetic attraction occurring when hydrogen binds to a higher or larger atom such as nitrogen.
Note that , the bond existing between two hydrogen atoms resulting in the formation of a molecule of hydrogen gas is covalent bond. Covalent bond can simply be explained as the sharing of electrons.
The study of chemicals and bonds is called chemistry.
The correct answer is A which is Two hydrogen atoms joining together to form a molecule of hydrogen gas.
What is a hydrogen bond?The bond formed between the hydrogen is called a hydrogen bond.The electromagnetic attraction existing between hydrogen and another electronegative atom, such as nitrogen or oxygen, is known as a hydrogen bond. It can also be explained as the electromagnetic attraction occurring when hydrogen bonds to a higher or larger atom such as nitrogen.
Note that, the bond existing between two hydrogen atoms resulting in the formation of a molecule of hydrogen gas is a covalent bond.
A covalent bond can simply be explained as the sharing of electrons.
Hence, the answer is mentioned as described.
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Explain the relationship between the terms chromosome
Answer:mdkcjcjcjc
Explanation:jdjdmdjdmc
Answer:
What is a chromosome? In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Which statements explain how lakes form? Check all that apply. Lava flows block a river. Streams flow into shallow areas. Groundwater feeds into low-lying areas. Ice sheets leave depressions that fill with water. Movement of Earth's crust creates low areas that fill with water.
Options A,D,E
lakes formed by:
Lava flows block a river.Ice sheets leave depressions that fill with water. Movement of Earth's crust creates low areas that fill with water.Explanation:
Lakes that develop in the holes of volcanoes are infinite in regions that are obedient to volcanic action. Lava spills from volcanic action can also create lakes. Enormous chunks of ice are sliced off and concealed by silt and pebbles. Meanwhile, the ice melts, the grit and pebbles cave in, bequeathing a deep gap at back.
These stew pots may produce substantial quagmires or lakes. As the huge portion of ice flows, outpourings design below the icebergs. A depression develops when an inadequate segment of the earth’s crust divides, ending in an earthquake. Rainfall and groundwater may accumulate in this depression, producing a lake.
You are accidentally stuck with a needle used to administer a medication to a patient with a known history of hepatitis B. You have already completed your hepatitis B vaccine series. In this case, which of the following statements is true?A) You need to report the needle stick to your supervisor as soon as possible.B) You have complete protection from hepatitis B and no further action is needed.C) You have two weeks from the time of exposure to start medical care for a potential infection.D) You will have to get another series of three vaccines to give you protection in the future.
Answer:
A) You need to report the needle stick to your supervisor as soon as possible.
Explanation:
To begin, every accident in a hospital has to be immediatly reported to the supervisor in charge. Even if it wasn´t harmful, there are several forms that have to be filled in order to avoid further accidents.
Also, the supervisor has to follow the procedures needed. In this case, even though you have all the vaccines, in order to prevent any symptom, you have to be in medication immediatly, not in two weeks but right away.
The other set of vaccines is not needed because you were already in contact with the infection and your inmunity system already made defenses for further exposures.
Which figurative language technique is used in the sentence: "I couldn't have lived without giving you a present."
answer choices
onomotopoeia
simile
personification
hyperbole
Neuroimaging techniques such as PET suggest a link between Capgras syndrome and abnormalities in each of the following brain regions EXCEPT the?
Answer:
fusiform face area.
Explanation:
What kind of speciation has occurred in this example, and what has driven it? Beetle pollinators of a particular plant are attracted to its flowers bright orange color. The beetles not only pollinate the flowers, but they mate while inside of the flowers. A mutant version of the plant with red flowers becomes more common with the passage of time. A particular variant of the beetle prefers the red flowers to the orange flowers. Over time, these two beetle variants diverge from each other to such an extent that interbreeding is no longer possible.
A. Allopatric speciation, ecological isolation
B. Sympatric speciation, habitat differentiation
C. Allopatric speciation, behavioral isolation
D. Sympatric speciation, sexual selection
E. Sympatric speciation, allopolyploidy
Answer:
B. Sympatric speciation, habitat differentiation
Explanation:
In the given example, no geographical barrier has been operational to isolate the two populations of the beetles so as to prevent interbreeding between them. On the other hand, the two variants are present together while developing isolating reproductively from each other. Therefore, it represents sympatric speciation.
The two variants mate inside the flowers of different colors. Since their mating sites are different colored flowers, they are not able to interbreed. This represents habitat differentiation as the one variants of beetle reproduce inside orange the colored flowers while the other inside the red-colored flowers. They develop a tendency to reproduce inside the different habitats (a habitat is a region where an organism lives and reproduces).
The nurse is instructing a patient with recurrent hyperkalemia about following a potassium-restricted diet. Which of the following patient statements indicates the need for additional instruction?
a) "I need to check if my cola beverage has potassium in it."
b) "I will not salt my food, instead I'll use salt substitute."
c) "I'll drink cranberry juice with my breakfast instead of coffee."
d) "Bananas have a lot of potassium in them, I'll stop buying them."
Answer:
"I will not salt my food, instead I'll use salt substitute."
Explanation:
Hyperkalemia may be defined as the medical condition in which the individual has high level of potassium in the body. This hyperkalemia can cause different diseases like cardiac arrest and can also cause death.
The hyperkalemia must be treated on time. The individual must be on low potassium diet. Avoid medicines that can increase the potassium levels and the administration of the sodium bicarbonates. The salt that has low potassium and high sodium concentration must be included in the diet.
Thus, the correct answer is option (b).
The carrying capacity of a wildlife reserve is 570 individuals for a particular species of rodents. If the area of the reserve is extended,
the carrying capacity is likely to
. During the summer, a fatal disease began killing individuals. The carrying
capacity of the reserve will therefore
Answer:
The carrying capacity of a wildlife reserve is 570 individuals for a particular species of rodents. If the area of the reserve is extended, the carrying capacity is likely to Increase
During the summer, a fatal disease began killing individuals. The carrying
capacity of the reserve will therefore decrease
Explanation:
The carrying capacity of a habitat is the maximum number of individuals of a given species it can support without depleting the available resources. When the area of the reserve is extended, the carrying capacity increases because the available resources will also increase. A fatal disease would increase the carrying capacity since the number of wildlife would decrease.
Carrying capacity -K- is the capability of the environmnet to support a growing population. A) Increase. B) Decrease.
What is carrying capacity?Carrying capacity, K, refers to the maximum point at which the environment can support a growing population.
K is a constant. It coincides with the population size when natality rate and mortality rate are equal to each other. This is the equilibrium point.
Commonly environments have limited resources and space, and as the population grows, competition and other interactions increases too.
The per capita growth rate decreases as population size increases. Finally, the population reaches the maximum point of carrying capacity, delimited by available resources, such as food or space and other factors. When the population size exceeds K, carrying capacity, the population decreases in size.
The carrying capacity might be affected by limiting factors, which might be a result of the population density (for example, competition) or might be density-independent. This last case refers to dense-independent factors, and among these, we can mention human impact or natural disasters (fires, volcanic eruptions, flooding).
In the exposed example,
A) If the area of the reserve is extended, the carrying capacity is likely to increase. This is because the bigger the area is, the more available resources there are, so populations can keep growing in size.B) If a fatal disease began killing individuals, the carrying capacity of the reserve will therefore decrease. There is a factor -disease- that is making the population decrease in size.You can learn more about carrying capacity at
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Which of the following type of immune cells are mismatched with their functions? Group of answer choices memory T-cells—mediate apoptosis cytotoxic T-cells—destroy virus-infected cells helper T-cells—secrete cytokines to control immune responses plasma cells—secrete antibodies
Answer:
Memory T-cells—mediate apoptosis
Explanation:
T-lymphocytes on maturation form many types of T cells like a cytotoxic cell, helper T cell, regulatory T cell, memory T cell and others.
The cytotoxic T cells and helper T cells are the major T cells which play important role in eliminating the pathogen as the Helper T cell produces cytokines which stimulate other immune cells and Cytotoxic cells kill the virus intracellular antigens or virus-infected cells.
The Plasma cells secrete antibodies which interact with an antigen and eliminate the pathogen but the memory T cells formed after the interaction with antigen does not mediate apoptosis but they provide a rapid immune response to the infection that has affected in the past by proliferating themselves into effector cells.
Thus, Memory T-cells—mediate apoptosis is the correct answer.
A researcher introduces double-stranded RNA into a culture of mammalian cells. The double-stranded RNA corresponds to a region of a protein-coding gene of interest. How may the introduced RNA affect gene expression in these cells?
Final answer:
Introducing double-stranded RNA into mammalian cells can initiate RNA interference, leading to the degradation of complementary mRNA and subsequent downregulation of the target protein synthesis, thus affecting gene expression.
Explanation:
Effects of Double-Stranded RNA on Mammalian Gene Expression
When double-stranded RNA (dsRNA) corresponding to a specific protein-coding gene is introduced into mammalian cells, it can trigger the process of RNA interference (RNAi). This occurs as the enzyme DICER attaches to the dsRNA and cleaves it into short fragments. A single strand from these fragments is then incorporated into the RNA-induced silencing complex (RISC). The RISC searches for and binds to an mRNA that is complementary to the RNA fragment. If a match is found, the mRNA is targeted for degradation, effectively silencing the gene from which the mRNA was transcribed. This leads to a decrease or complete cessation in the production of the protein coded by the gene, impacting gene expression in the cells.
The RNAi pathway is a critical regulatory mechanism in cells, used not only for developmental processes but also as a defense against viruses. Upon the introduction of siRNA or miRNA, the RISC complex can either cleave perfectly matched mRNA or inhibit translation if the miRNA is not fully complementary. This post-transcriptional regulation is an important tool in controlling gene expression and is leveraged in research and therapeutic interventions.
Final answer:
Double-stranded RNA introduced into mammalian cells activates RNA interference (RNAi), leading to the degradation of mRNA with a matching sequence, thereby reducing gene expression temporarily. Continuous gene suppression is achievable with shRNA synthesized by the cell.
Explanation:
When double-stranded RNA (dsRNA) is introduced into mammalian cells, it engages a cellular mechanism known as RNA interference (RNAi) which affects gene expression. Researchers Mello and Fire discovered that dsRNA, not single-stranded antisense RNA, interfered with gene expression, chopping up the dsRNA into smaller fragments that block mRNA's function in protein synthesis. The enzyme DICER attaches to the dsRNA and cuts it into short fragments. These fragments are then incorporated into the RNA-induced silencing complex (RISC), which degrades any mRNA matching the sequence of the RNA fragment.
Furthermore, the use of a DNA vector encoding a small hairpin RNA (shRNA) allows for the continuous synthesis of sequences against a specific gene in mammalian cells. The shRNA is processed into typical siRNA molecules that maintain the RNAi effect for an extended period. This technique has practical applications, such as creating caffeine-free coffee plants through genetic engineering, representing a significant advancement in RNAi technology.