Expression Definition and 999 Threads

Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. These products are often proteins, but in non-protein-coding genes such as transfer RNA (tRNA) and small nuclear RNA (snRNA), the product is a functional non-coding RNA. Gene expression is summarized in the central dogma of molecular biology first formulated by Francis Crick in 1958, further developed in his 1970 article, and expanded by the subsequent discoveries of reverse transcription and RNA replication.The process of gene expression is used by all known life—eukaryotes (including multicellular organisms), prokaryotes (bacteria and archaea), and utilized by viruses—to generate the macromolecular machinery for life.
In genetics, gene expression is the most fundamental level at which the genotype gives rise to the phenotype, i.e. observable trait. The genetic information stored in DNA represents the genotype, whereas the phenotype results from the "interpretation" of that information. Such phenotypes are often expressed by the synthesis of proteins that control the organism's structure and development, or that act as enzymes catalyzing specific metabolic pathways.
All steps in the gene expression process may be modulated (regulated), including the transcription, RNA splicing, translation, and post-translational modification of a protein. Regulation of gene expression gives control over the timing, location, and amount of a given gene product (protein or ncRNA) present in a cell and can have a profound effect on the cellular structure and function. Regulation of gene expression is the basis for cellular differentiation, development, morphogenesis and the versatility and adaptability of any organism. Gene regulation may therefore serve as a substrate for evolutionary change.

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  1. L

    Complex exponentials (simplify the expression)

    1. Simplify ei6x(1+e-i10x)/(1+ei2x) 2. i have no idea how to simplify this its supposed to be in terms of cosines 3. i don't how i can simplify this such that i can use the 1/2(e^x +e^-x) = cosx formula
  2. Q

    The integral of the taylor expansion of any expression

    ok .lets say the expression we have is ex the taylor expansion becomes 1+x+x2/2+... integrating becomes x+x2/2+x3/6+...+c so how do we know that c = 1? for it to become back to ex becos it is said that integral of ex = ex do we just let x be 0 to find c = 1? does it work for all...
  3. N

    Rewriting Expression Homework: Tips & Hints for Solving

    Homework Statement Hi I have an expression on the form \frac{\tau }{{\alpha - \varepsilon + i\eta }}\left( {1 + \frac{\tau }{{\alpha - \varepsilon + i\eta }}G} \right) where i denotes the complex i. I have to bring this into the form \frac{\tau }{{\alpha - \varepsilon +...
  4. A

    What Are the Equilibrium Concentrations and Kc for 2NO(g) + Br2(g) ⇌ 2NOBr(g)?

    Given 2NO(g) + Br2(g) <--------_____> 2NOBr(g), Concentration (M) [NO] [Br2] [NOBr] Initial 2.5 5.0 1.0 Change P Q...
  5. B

    Jackson - p. 35 - integral of certain expression

    Homework Statement The expression {\textstyle{{3{a^2}} \over {{{({a^2} + {r^2})}^{5/2}}}}} has a volume integral equal to 4\pi for arbitrary "a". Homework Equations The Attempt at a Solution \int_0^R {\int_0^{\pi /2} {\int_0^\pi {{\textstyle{{3{a^2}} \over {{{({a^2} + {r^2})}^{5/2}}}}}...
  6. H

    What is the expression for the entropy S(T)?

    Homework Statement Compute and plot the entropy S(T) for the truncated system. My actual question is what the function S(T) should be. Homework Equations Consider a bound single-particle system with a discrete, equidistant (spectral constant = delta e) energy spectrum. epsilon_j...
  7. H

    Closed form expression for the partition function Z using the Canonical Ensemble

    Homework Statement I'm looking for a closed form expression for the partition function Z using the Canonical Ensemble Homework Equations epsilon_j - epsilon_j-1 = delta e Z = Sum notation(j=0...N) e^(-beta*j*delta e) beta = 1/(k_B*T) t = (k_B*T)/delta e N is the number of excited...
  8. T

    Rearranging an expression in sqrt argument

    Homework Statement Rearranging an equation...can't quite see how it's done. Homework Equations r=\sqrt{2.5^{2}cos^{2}(t/2)+5^{2}sin^{2}(t/2)} r=2.5\sqrt{cos^{2}(t/2)+4sin^{2}(t/2)} r=2.5\sqrt{1+3sin^{2}(t/2)} The Attempt at a Solution I know that cos^{2}(x)+sin^{2}(x)=1 but...
  9. K

    How to eliminate imaginary parts of complex expression?

    Hi, I have a problem on how to convert the imaginary parts of expression into all real parts. For example: x1 = - (a + ib) x2 = (a + ib) x3 = - (a - ib) x4 = (a - ib) My question is that how to express x1, x2, x3 and x4 in terms of real parts only without imaginary parts. I have used...
  10. O

    Derive expression for Klein-Gordon annihilation operator

    [/tex]1. Homework Statement [/b] Given: \phi(x)=\phi^+(x)+\phi^-(x) Where: \phi^+(x)=\sum_{\mathbf{k}} \sqrt{\frac{\hbar c^2}{2 V \omega_{\mathbf{k}}}} a(\mathbf{k}) \mathrm{e}^{-\mathrm{i}kx} and \phi^-(x)=\sum_{\mathbf{k}} \sqrt{\frac{\hbar c^2}{2 V \omega_{\mathbf{k}}}} a^\dagger...
  11. P

    Derive an expression for the Fermi energy of a 2D structure at 0 kelvin?

    Homework Statement That's basically the whole question in the title there, ie; Derive an expression for the fermi energy of a 2d structure at 0 kelvin. 2. The attempt at a solution Basically the first part of the question had us sketching the Fermi-Dirac distribution function at 0K for...
  12. I

    Advice on a book for expression manipulation?

    Books for self-teaching previously taken math courses, and other problems :) What I want to focus on: While I am a CS student, I am also interested in mathematics subjects as a whole and want to re-familiarize myself with some of the courses I took in the past. I received high grades, but to...
  13. N

    Expression of Gravitational Potential in GR

    Hello everyone...can anyone tell me what is the modified expression for the gravitational potential in GR which takes into account the fact that the speed of gravity is finite (c, to be precise)...In fact, it may be a non-sense question as I haven't started to read GR yet...Is there any...
  14. R

    Factoring a very long expression

    Factoring a very long expression! please help (x^6) - (4x^5) + (x^4) + (10x^3) - (4x^2) - (8x) then: x((x^5) - (4x^4) + (x^3) + (10x^2) - (4x) - 8) my teacher skipped many steps and ultimately found: x * [(x+1)^2] * [(x-2)^3] I guess he's assuming we know how to get through it. Can...
  15. N

    Does this expression has an exact solution?

    how to solve this hamilition? and Does this expression has an exact solution?
  16. V

    1/4th Life expression for First Order Rxn

    I must derive the 1/4th life expression for a first order rxn. ln(\frac{[A]_{\circ}}{[A]_{t}})=kt ln(\frac{[A]\circ}{\frac{1}{4}[A]_{\circ}})=kt_\frac{1}{4} ln(4)=kt_{\frac{1}{4}} do I set t=1/4 ? \frac{ln(4)*4}{k} \frac{5.545}{k} What am I doing wrong here? The answer is allegedly...
  17. J

    Sketch and make an algebraic expression to model graph

    Homework Statement Sketch the graph of a function g(x) with a corresponding domain on (-5, infinity) whose first derivative is always positive and whose second derivative is always negative. Then come up with and algebraic expression to model your graph. Homework Equations The Attempt at a...
  18. F

    Convert Expression to Sum of Prod & Prod of Sums

    Homework Statement Convert the following expression into sum of products and products of sums (AB+C)(B+C'D) Homework Equations Distributive Property The Attempt at a Solution for product of sums it would be (AB+C)(B+C'D) since it is already in this form. When calculating sum of...
  19. R

    Manipulate partial derivatives to obtain desired physical expression

    Homework Statement Show that the expression A, T(dP/dT)|V - P is equal to expression B, T^2 * [d(P/T)/dT]|V Also, show that expression C, -[d(P/T)/d(1/T)]|V is also equal to expression B Homework Equations A: temperature * (dPresure/dTemperature at constant volume) -...
  20. L

    Write out the expression for the vertical velocity

    Homework Statement Given z(t) as above, write out the expression for the vertical velocity Homework Equations z(t)=Asin(vt) where z(t) is the vertical position of a test particle, A is the amplitude of its motion, and t = 0 is the time when the particle is at the midplane The...
  21. W

    How can I simplify this complex expression?

    I need the following expression simplified. 36/[64.4*(0.5+(2+ x)*((1-(1/4)*x^2 )^0.5)) ]-x*((1-(1/4)*x^2 )^0.5)=0
  22. B

    How do I work out an expression for the total energy

    Homework Statement Black body radiation inside a cavity at temperature T may be thought of as a gas of photons with an energy distribution given by the function n(E) given by n(E)dE = A [E^2 / (e^(E/kT) - 1) ] dE Where A is independent of E and T. (k is Boltzmann constant) The...
  23. M

    Use work/energy throem to derive an expression for moment of inertia?

    Homework Statement Today I had a physics lab. It involved a hanging mass on a string that hung off the table. It went through a pulley and the string was then spooled around a rotating spool on the table. We first measure the radius of the spool. Then we figured out the mass it took to...
  24. Q

    Need help simplifying expression

    The Attempt at a Solution I'm attempting to solve a question with a few unknowns, and I managed to get it to the following form: tanx(1-cosx)=0.25 I just can't seem to simplify it further and thus solve.. Any ideas?
  25. K

    Converting a boolean expression into simplest product of sums

    Homework Statement Given F = (A'+B')[ABD' + A'C + A'BD], simplify into a simplest product of sums.Homework Equations The Attempt at a Solution Multiplying through gives me A'BD + A'C. I have tried expanding, adding consensus terms, but I'm not sure how to take it from there. Additionally, I...
  26. T

    Finding the limit of this expression

    Homework Statement The limit of \frac{8x^3+x^2-5x}{3x^4-5x^2+2} as x goes to 1Homework Equations Evaluate this limit algebraically.The Attempt at a Solution Tried using 1 instead of x. The denominator becomes 0. Divided denominator by (x-1) but couldn't continue.
  27. A

    Blackbody radiation - derive expression for T

    Homework Statement Derive an expression for the temperature of an ideal blackbody so that its radiated light at the peak intensity wavelength has exactly enough energy to excite the ground state to fourth excited state. Homework Equations I = σ*T4 λm*T = 2.9 * 10-3 m * K E = hf = hc/λ...
  28. D

    When is an expression Big O, Big Omega or Theta?

    I understand how to compare 2 functions and tell which bound they are in... but what I cannot comprehend is, given a single function... how do you write which bound it is in? Given a simple for loop like : for(int i = 0; i<n; i++) { for(int i = 0; i<j; i++) { System.out.println("Haha.")...
  29. R

    Take the derivative of rational expression

    Homework Statement f(x) = \frac{x}{x-1} + \frac{x+1}{3x} Homework Statement need to take the first derivative of this expression... I can do it but I am curious as too why i cannot take the derivative of \frac{x}{x-1} and then just add it to the derivative of \frac{x+1}{3x}...
  30. S.Daedalus

    Are dualities not just an expression of equivalence in physical theories?

    By 'equivalence', I mean of the computational kind -- i.e. in the same way any universal computer can emulate any other. First of all, hi there, I'm not sure I put this question in exactly the right forum, but it seems to me that most dualities currently being discussed fall under the...
  31. D

    Relative Velocity and Position of Ships A and B: Solving for Least Separation

    Ship A is located 3.3 km north and 2.7 km east of ship B. Ship A has a velocity of 22 km/h toward the south and ship B has a velocity of 40 km/h in a direction 37° north of east. (a) What is the velocity of A relative to B? (b) Write an expression for the position of A relative to B as a...
  32. R

    System equilibrium constant expression

    Hello, geniuses! :) I am having a problem in chemistry... What is this systems equilibrium constant expression? And under what conditions (temperature, pressure, concentrations) you can most fully get rid of SO2? I really have no idea with what to start... :/
  33. B

    Total power of the sun with Rayleigh-Jeans expression

    Homework Statement What is the totaly power emitted by the sun over all wavelengths (frequencies) according to the (incorrect) classical Rayliegh-Jeans expression for ρt(v) Homework Equations ρt(v)dv=8piv^2kT/c^3 dv The Attempt at a Solution I'm not sure how to start this one...
  34. P

    Is this considered a closed expression for pi?

    ln(-1)/i=pi this equation does not use limits or integrals, as you can see, but it does involve imaginary numbers. Does this make it an open expression, or does the fact that it uses i not matter?
  35. A

    Simplification of regular expression

    So is there any set of defined rules that help in the simplification of regular expressions? Because till now I would simply try and look at the patterns and see whether this or that simplified version would generate the same.Intuitive, but now always fast or correcct. So is there any...
  36. S

    Find the derivative of a complicated expression

    Homework Statement Find dP/dt of 2048000(t^2)(e^1600t)+5120t(e^-1600t)+3.2(e^-1600t) Homework Equations The Attempt at a Solution 2048000(2t(e^-1600t)-1600(t^2)(e^-1600t))+5120((e^-1600t)-1600(e^-1600t))+3.2(-1600(e^-1600t)) After moving the t over to simply the first part and...
  37. B

    Calculating an expression for the charge in a capacitor?

    Homework Statement hi I'm new and thanks in advance! I'm trying to work out a problem I've been given but having difficulties! I am given a scope for the current in a capacitor and I'm trying to determine the expression of charge in the capacitor firstly, then when t = 10ms Homework...
  38. A

    Conformal time analytical expression

    Hi all, Anybody pls help me to convert cosmic time to conformal time (numerically)... is there any analytical expression for conformal time, \tau , except d\tau=dt/a(t) ? can we approximate \tau \approx -1/aH ?? pls help... Anuradha
  39. M

    Differential Equation expression help

    Here's the question: Let f be the function satisfying f'(x)=x\sqrt{f(x)} for all real numbers where f(3)=25. a. Find f''(3) b. Write an expression for y-f(x0 by solving the differential equation \frac{dy}{dx} = x\sqrt{y} with the initial condition of f(3)=25. For a, I got...
  40. A

    Factorize the following expression

    Homework Statement Expression is p^3-(x^2+xy+y^2)p+xy^2+x^2y=0 where ^ shows power Homework Equations The Attempt at a Solution the solution is (p-x)(p-y)(p+x+y)=0
  41. S

    Developing a divergence expression

    Hi all, I'm trying to fill in some mathematical steps from a derivation I'm reading in a research paper. I want to see that the following expression \text{Div}\left(\nabla u\frac{ \phi ' \left(|\nabla u|\right)}{|\nabla u|}\right) is equivalent to (\frac{\phi '...
  42. A

    Expression of Electric Field with known charges

    Homework Statement I have 2 charges: Q1 = 300 uC located at (1, -1, -3) m Q2 = ?? uC located at (3, -3, -2) m Q1 feels a force from Q2 of F1=(8i - 8j + 4k) N 1. Find Q2 2. Find the expression of the E-Field at (3, -3, -2) m (at Q2) Homework Equations F=(k|Q1*Q2|) / r^2 E=(k|q|)...
  43. H

    Representing sum of cosine and sine as a single cosine expression

    a.cos(wt) + b.sin(wt) = M.cos(wt + ϕ) Can you give me M and ϕ in terms of a and b?
  44. L

    English expression - not stacionary heat flux

    Hi, I am doing an experiment. I am heating a sample and changing a temperature on one surface of the sample as a sine function of time. Measuring heat flux I am trying to predict heat response of the sample. After some sine cycles heat response is in every next sine cycle the same. How do you...
  45. L

    Landau's derivation of the Langangian expression

    I'm going over the Landau's Mechanics, and can't get over two hurdles. The first is the following(I'm not good with latex here, so please bear with me): Landau asserts that the action S' between t1 and t2 of a Lagrangian L such that L is a function of (q+dq) and (q'+dq') minus the action S...
  46. T

    Deriving an expression using Bernoullis equation.

    Hi! This is my first post, so i apologise if i leave out any information. I need to derive an expression for the theoretical velocity of flow in an open channel using the Bernoulli Equation. I realize it is probably a simple question but i am sort of a beginner. Any help appreciated...
  47. T

    Writing A Trig Expression as an Algebraic Expression

    Homework Statement Write the Trigonometric Expression as an algebraic expression. cos(2arccos 2x) Homework Equations Probably the inverse properties, I'm not sure. The Attempt at a Solution I know I can rewrite this equation as. u= arccos 2x cos(2cos u=2x) I can also...
  48. J

    Simplifying an Expression using Logarithms

    Ok, I have an Expression which is attached and it needs simplifying. What I have done is got 12logx But I don't think this is correct. Another possible place I got to is logx4/logx1/3 Which one is it?
  49. J

    Simplifying Expression using Logarithms

    Simplify the attached expression using any relevant logarithmic rules I haven't really done much with logarithms, so i didnt know where to start?
  50. B

    How to Derive Spectral Intensity for a Laser Pulse?

    Homework Statement Electric field for a single pulse of a laser (operating at central wavelength of 800nm): E = E0e^(-(t^2/2a^2))e^(iwt) (the a is sigma and w is omega) Derive an expression for the spectral intensity (irradiance) The Attempt at a Solution One way I know to...
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