What is Expression: Definition and 999 Discussions

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. P

    Analytical expression of the impedance of a CPW ground

    Hi, I am trying to understand the calculation of the characteristic impedance of a CPW ground. I need to get an analytical expression for the impedance. My first step was to read the book: "Coplanar_waveguide_circuits__components__and_systems" Here is what I don't understand: the...
  2. G

    Finding an expression for linear acceleration of a hanging mass

    A rope of negligible mass is wrapped around a uniform solid cylinder, of radius R, that can rotate freely about its axis, which is horizontal and fixed. A block hangs vertically from the rope and causes the cylinder to spin. The blocks mass, M_B is 4 times the mass, M, of the cylinder. Find an...
  3. T

    Finding an expression for the series

    Homework Statement 1+2x+(4!x^(2))/((2!)^(2))+(6!x^(3))/((3!)^(2))+(8!x^(4))/((4!)^(2))+... Homework Equations Uhhhhh... The Attempt at a Solution Well, the denominator looks like it's going to be (n!)^2. And this expression appears to be using values of N≥0. But I'm not so sure...
  4. D

    Gradient of a complex expression

    Hello, My question is concerning how to compute the complex gradient of the following cost functional with respect to W: F=Ʃ_i=1:M ||y_i-Go*W_i||^2 + Ʃ_i=1:M ||W_i - X*(E_i - Gc*W_i)||^2 Where the summations go from i=1 to i=M and the dimensions of the diferent elements are: y: Nx1 Go: Nxn W...
  5. DryRun

    Prove trigonometric expression

    Homework Statement Prove that sec^(2)(x/2) divided by 1 - tan^(2)(x/2) is sec x Homework Equations Trig identities. The Attempt at a Solution I used the identity: 1 + tan^2(x) = sec^2(x) I get for numerator: 1 + tan^2(x/2) I kept denominator same: 1 - tan^2(x/2) I get the...
  6. R

    Deriving a scale factor expression for FLRW model

    Hello, I am reading this paper about quantum gravity, trying and failing to follow along in the derivation of this, eq (204) p. 72, expression for the scale factor: a(t) = a_1 \left( 1 + \frac 3 2 ( 1 + \omega ) H_1 (t - t_1) \right)^{\frac 2 {3(1+\omega)}} (I'm not sure what the...
  7. A

    Pauli Matrices: Calculating Expression

    Hey guys, I was wondering how to get the expression for pauli matrices. I know that for one electron: S_i = \frac{\hbar}{2} \sigma_i But I also know that you can get to the above expression by explicitly calculating the matrix elements of the Sz, Sx and Sy operators (in the basis generated...
  8. Z

    Question about taking the difference between two square root expression

    In Ramakrishna's paper, http://arxiv.org/ftp/arxiv/papers/1111/1111.1922.pdf , he derived equation (9), page 5. It is a difference of two square-roots using an approximation method. Can anyone help in how this is done? Thanks
  9. S

    Simplest algorithm for computing the resultant of a boolean expression?

    hi, let's take something simple, for example: (a>b) && ((b>c) && c>d) || (d > c) Intuitively, it's easy to work out given the values of a, b, c and d and just evaluating the brackets in order of precedence. i.e. Is b > c?? then is c > d Then in addition to the above answer being...
  10. Q

    Formulating the correct least action expression

    I am trying to understand how, for a given physical system it is possible to come up with the correct expression for the lagrangian and thence the least action formulation from which the governing equations can be derived by application of the euler lagrange equation. From what I have seen so...
  11. B

    Obtain an expression for the expectation value in terms of energy

    Homework Statement The ground state wave function for a particle of mass m moving with energy E in a one-dimensional harmonic oscillator potential with classical frequency omega is: u(subscript 0) (x)= N(subscript 0) exp((-alpha^2)(x^2)/2) and alpha=sqrt (m *omega/h-bar) where...
  12. L

    Reduce the expression to xor and or xnor

    Homework Statement Reduce the expression to one that just contains xor and/or xnorHomework Equations (A'B'C')+(A'BC)+(ABC')+(AB'C)The Attempt at a Solution C'(A'B'+AB)+C(A'B+AB') C'(A\ominusB)+C(A\oplusB) not really sure what to do next.Do the C' and C cancel each other out?
  13. E

    Integer values of this expression

    Is there a simple way to find the integer values of f(x)=(a+5x)/(6x+1) with a, x integers.
  14. G

    How can I find x in terms of c for this expression?

    Homework Statement With f(x)=-\lgroup\frac{a}{2}-\frac{x}{2b}\rgroup\ln\lgroup\frac{a}{2}-\frac{x}{2b}\rgroup-\lgroup\frac{a}{2}+\frac{x}{2b}\rgroup\ln\lgroup \frac{a}{2}+\frac{x}{2b}\rgroup and z=\frac{df}{dx}=\frac{1}{c} find an expression of x in terms of c. Homework...
  15. M

    Boolean Expression Simplification

    Homework Statement Simplify the following expressions (x'y'+xy'+x'y) (p+q'p)(p+qr) Homework Equations Laws of boolean algebra The Attempt at a Solution For the first one I've found many ways to solve it... something isn't right here (x'y'+xy'+x'y) =x'(y'+y)+xy' =x'+xy'...
  16. D

    Reduce the boolean expression as much as possible

    Homework Statement Reduce, x(w+y'+z') + (w+x)y'z + wx'yz + wxy Homework Equations + stands for OR * (multiplication) stands for AND ' NOT The Attempt at a Solution I tried to combine some terms but I cannot find a good start... x(w+y'+z') + (w+x)y'z + wx'yz + wxy = xw + xy'+...
  17. D

    Simplify boolean expression (a+b+c)*(a'+c)*(a'+b')

    Homework Statement I need to simplify the boolean expression by algebraic manipulation as much as possible. (a+b+c)*(a'+c)*(a'+b') Homework Equations + stands for OR * stands for AND (or no operator between variables) ' Stands for NOT The Attempt at a Solution I tried but I do not...
  18. C

    Need help finding a strange vector system expression.

    Homework Statement A toy cart of mass M1 moves on frictionless wheels as it is pulled by a string under tension T. A block of mass M2 rests on top of the cart. The coefficient of static friction between the block and cart is μ. The cart is moving up a ramp at angle θ. Find an expression for...
  19. J

    Finding an expression for the maximum tension?

    A toy cart of mass m1 moves on frictionless wheels as it is pulled by a string under tension T. A block of mass m2 rests on top of that cart. The coefficient of static friction between the cart and block is μ. Find an expression for the maximum tension T that will not cause the block to slide on...
  20. A

    Create an expression for a rotating plate

    A flat, circular plate (mass Mp, radius Rp, thickness Tp) rotates parallel to the surface of the Earth on a frictionless axle. As it spins, a point on the top of the disc traces a circle each time the plate completes a rotation. in terms of the number of rotations per minute (N/min), create...
  21. V

    Write the trigonometric expression as an algebraic expression in u.

    Homework Statement csc(cos^-1 u) Homework Equations Fundamental identities properties The Attempt at a Solution The book is incredibly vague on how to do this. I tried multiplying csc by (cosθ/cosθ) to get cotθ*secθ. I'm not sure if this is the right thing to do, or what to do...
  22. M

    Formulating an expression

    I'm having trouble trying to decipher this: A number U is on the unit interval. Write the algebraic expression for "U differs from 0.5 by more than 0.25" This is what I did...am I doing this correctly? 0.5-U > 0.25 after doing the algebra U < 0.25
  23. I

    Expression of Acceleration and velocity

    Homework Statement The position of an object of mass m is given by: http://imageshack.us/photo/my-images/62/20110920161443.jpg/ Find expression for the velocity and the acceleration and deduce the force components acting on the particle. Homework Equations W = vr, v = u+at , f = ma v = d/t...
  24. I

    Find an expression of acceleration

    Homework Statement A particle has mass m = 0.1 kg , has a velocity which is given as: v = 3.2i+4.3j+5.4k m/s It's acted by force f = 7.1i+8.2j+9.3k The questions which arise are: i) Find the speed of the particle. ii) Write down a unit vector in the direction of the velocity. iii)Find...
  25. X

    Finding the expression for the horizontal acceleration

    Hey folks its me again! The problem at hand gives me a potential energy function ( V(x) ) that defines the height of a particle in motion. Next to the problem is a picture of a curvy graph that is y vs x. It asks to find the expression for the horizontal acceleration. This is what I did...
  26. B

    What is the expression for the inverse matrix of A?

    1. a) Prove the following holds for A A is a matrix [a b, c d] I is identity matrix. A^2 = (a+d)A-(ad-bc)I. b) Assuming ad-bc not equal to 0, use a) to obtain an expression for A^-1. The Attempt at a Solution I proved the first equation, but I'm not seeing where it relates to...
  27. D

    Cascading low pass op amps, derive expression for f3db

    Homework Statement consider the cascading of two non identical amplifiers stages, each having a low-pass STC frequency response. STage 1 has a low freqency gain of ALF1 and a 3 dB frequency of f1. Stage 2 has a low frequency gain of ALF2 and a 3 dB frequency of f2. Derive a polynomial...
  28. 1

    Expression for Variances in X with Respect to W, Y, and Z

    Homework Statement Determine the expression for the variances in x (that is \sigma2) with respect to the appropriate variables for the following: a) X = \frac{wy}{z}, with variance in w,y,z Homework Equations I'm having trouble typing out the equation, but the equation I know for...
  29. J

    Alternate expression for Maxwell's Equations

    Hello, I'm prepping for a course I'm about to take and on the pre-course syllabus it said I should be able to: "Derive the equations for E and H fields in terms of magnetic current source M." It's been a long time since I've had an EM course, so I'm naturally lost. How would I go about...
  30. D

    The Attempt at a SolutionSolution to Integral using Leibniz Rule & IB Parts

    Homework Statement Using Leibniz rule and integration by parts, solve \frac{\partial}{\partial x} \int_0^y u dy. Homework Equations u = U(x) f' (\eta) \eta = \eta(x,y) = y g(x)
  31. DryRun

    Simplify complex number expression into acos(wt+x)

    Homework Statement I could not type it here, so i made a screenshot and posted it below. Homework Equations it's about complex numbers undergraduate level. I'm currently doing Euler's formula and De Moivre's theorem, although I'm not sure that the solution lies there. The Attempt at...
  32. L

    Help deriving expression of current density

    Hey I got an assignment where I have to get an expression of the current density to be: j = -e\int \frac{dk}{4\pi ^{3}} v_{x}f(k) It says k_{x} >0 underneath the intergrale. The current is flowing to the right (velocity of v_{x} > 0) Where f(k) is the fermi-dirac distribution function...
  33. S

    Finding the interval of expression having two quadratic equations.

    Homework Statement What will be the values of 'm' so that the range of the equation y= \frac{mx^2+3x-4}{-4x^2+3x+m} will be all real values i.e. y\epsilon (-\infty,\infty)given:x can take all real values. any help or hint will be appreciated. Homework Equations The Attempt at a Solution i...
  34. U

    Determine the negation of the expression

    The question states: Determine the negation of the expression. p -> q ^ r. I am having difficulty finding the negation. Below are the steps I have taken in an attempt to come to the solution. The - symbol will be the negate symbol. p -> q ^ r (-p OR q) ^ r -(-p OR q) ^ r...
  35. D

    Simplify each expression: 2/1+y-2 /2x^3+x

    Homework Statement 2/1+y-2 /2x^3+x its all over top of 2x^3+x Homework Equations The Attempt at a Solution should i multiply the top by 1+y, like the 2 and the -2.
  36. D

    Simplify each expression: 2(4-h)^2-32/h

    Homework Statement simplify each expression: 2(4-h)^2-32/h Homework Equations The Attempt at a Solution I forget if I should multiply the 2 into the 4-h.
  37. G

    Terms in a Mathematical Expression

    When we refer to terms in an equation, what EXACTLY are we referring to? Suppose for example we have: ab + bc + cd = A Suppose somebody refers to term "ab". Are they referring to the syntactical NAME "ab", the IMAGE of ab (i.e., it's value), or the ARGUMENT (a,b) which belongs to some...
  38. S

    Polynomial expression of Pendulum period with respect to angle (large)

    [b]1. Homework Statement The swinging period T(θ) for a small amplitude simple pendulum, is given by T, a constant for a constant length pendulum. If the initial angle θ is large, then the amplitude becomes large and the period needs to be corrected. The correction to the large amplitude...
  39. Alpharup

    What is the expression for work done in a perpendicular collision?

    I have studied in my lower grades that work(w) done or energy is the product of force(f) and displacement(s).Till now I was thinking that this was true. I was not taught that it was the dot product of force and displacement. according to this definition, the work done when the force and...
  40. V

    Inrectangular subintegral expression

    Normally, integration means summing the infinitesimal rectangles of height f(t) and width dt. The differential dt appears as a multiplier behind the integration mark, \int, therefore. But, what do you think about summing non-standard infinitesimal pieces, like \int{1 \over 1/dt + 1}? For...
  41. D

    Scientific Thinking Graphing -Determining the Mathematical Expression

    "Scientific Thinking Graphing" -Determining the Mathematical Expression Homework Statement Ok, so I recently got an assignment for "Scientific Thinking Graphing Practice". Basically, I need to take a data table that will produce a curve shaped graph and turn it into a straight lined graph...
  42. P

    Expression for the time average power dissipated in a resistance R

    Homework Statement A square loop with side-length a is positioned at the centre of a long thin solenoid, which has radius r (with r > a), length l and N turns. The plane of the loop is perpendicular to the 5axis of the solenoid. A current I = I0 sin ωt flows through the loop. Derive an...
  43. 1

    Find the derivative of the expression and simplify fully.

    Homework Statement k(x) = x^2(2x^3+x)^1/3 Homework Equations I used the product rule and the chain rule to get to the point that i did. The Attempt at a Solution dy/dx(x^2)(2x^3+x)^1/3 + dy/dx(2x^3+x)^1/3(x^2) = (2x)(2x^3+x)^1/3 + 1/3(2x^3+x)^-2/3(6x^2+1)(x^2) I can't...
  44. 5

    Find an expression for the nth partial sum using this identity

    Homework Statement The series, 1 / (1 x 2) + 1 / (2 x 3) + 1 / (3 x 4) + ... + 1 / [n(n + 1)] + ... is not a geometric series. (A) Use the identity 1 / [k(k + 1)] = 1 / k - 1 / (k + 1) to find an expression for the nth partial sum Sn and (B) use it to find the sum of the...
  45. P

    Two expression for relativistic acceleration

    Suppose a particle in frame S moves with acceleration a_{x} and velocity u_{x} at a given instance in the x-direction. I wanted to find the acceleration in a frame S' moving with velocity v in the positive x-direction with respect to frame S. To do this I used the following approach...
  46. M

    Why does this expression not have a vertical asymptote?

    Homework Statement Find the vertical asymptote, if there is one, of this rational function. \frac{\sqrt{16x^2 + 3x + 6} -5}{x-1} Homework Equations The Attempt at a Solution This was actually a Calculus problem, I had to find the limit at infinity. I was able to do that easily; an extra...
  47. C

    Horrible expression involving logs and inverse tan functions

    Homework Statement \frac{d^2y}{dx^2} + (y^4-1)\frac{dy}{dx} = 0 Homework Equations \frac{dy}{dx} + (y^4-1) = 0 The Attempt at a Solution \frac{dy}{dx} = (1- y^4) \frac{dy}{1- y^4} = dx Then I get a horrible expression involving logs and inverse tan functions...
  48. E

    Algebraic expression for triangles within polygons

    Homework Statement If a polygon has n>=4 sides, what is the probability, in terms of n, that a triangle made up of vertices of the polygon shares at least one side with the polygon. Homework Equations The Attempt at a Solution Treating vertices of polygons as possible outcomes...
  49. J

    Question about rewriting an expression with radicals

    Homework Statement (-3/x^(1/2)) / ((2/y^(1/2))-8) which, from my book, I see can be rewritten with radicals as: (-3/sqrt(x)) / ((2-8sqrt(y))/(sqrt(y)))The Attempt at a Solution Now, what I don't understand is how the denominator was rewritten. I understand that in the numerator, the 1/(...
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