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. J

    Can I apply L'Hopital's rule to this integral expression?

    Hi, Suppose I have \lim_{r\to 0} \left\{\int_0^{\pi} \frac{f(r,t)}{r^2}dt - \int_0^{\pi} \frac{g(r,t)}{r} dt\right\} and both integrals tend to infinity. So I combine them: \lim_{r\to 0} \int_0^{\pi} \frac{f(r,t)-r g(r,t)}{r^2} dt now at this point, the numerator in the...
  2. D

    Quantum - Find the formal expression of the coefficient cn(t=o)

    Quantum -- Find the formal expression of the coefficient cn(t=o) Hello everyone, I'm really stuck on the first question of an exercise, so I can't start! :cry: Homework Statement ψ(x,t) a wave function normalized and solution of Shrodinger equation for a given potential. I the...
  3. H

    Engineering Drawing a circuit diagram for a Boolean expression

    Homework Statement Draw the logic diagram for the following Boolean expression. The diagram should correspond exactly to the equation. Assume the complements of the inputs are not available. B(A'C'+AC) + D'(A+B'C) Homework Equations The Attempt at a Solution I can't find any...
  4. S

    What is the Sackur-Tetrode expression for the entropy of a monatomic ideal gas?

    Homework Statement Write the Sackur-Tetrode expression for the entropy of a monatomic ideal gas as a function of pressure, temperature, and number, S(N,T,P). Homework Equations S = Nk[ln(V/N(4πmU/3Nh2)3/2) + 5/2] PV = NkT U = (f/2)NkT The Attempt at a Solution I found that...
  5. V

    Expression of an object and its image onto a screen with two lens?

    Homework Statement Formulate an expression that gives the focal length of a corrective lens, to be used in conjunction with a fixed lens. You may assume that both lenses are on the same plane, i.e. that they are very close together. The corrective lens should allow an object at a specified...
  6. K

    What is the expression of N=2 SUSY transformation

    I have checked many textbooks and papers on SUSY and it seems that none of them mentions anything about the infinitesimal susy transformation on component fields in the case N\neq 1. So I am wondering what does it looks like, say for N=2 vector multiplet? Another related question is, do we need...
  7. L

    Simplify the boolean expression #2

    Homework Statement Simplify the expression using boolean algebra postulates, laws, theorems. (\overline{\overline{x + \overline{y})(xz + \overline{y}}) + x (\overline{yz}}) The Attempt at a Solution (\overline{\overline{x + \overline{y})(xz + \overline{y}}) + x (\overline{yz}}) 1. ((x +...
  8. L

    Simplify the boolean expression

    Homework Statement Build the truth tables for the boolean expressions. (x + y' * z)' + (x * y * z' + (y + z)') + (y + (x * z')')' The Attempt at a Solution Given that the expression is so complex I believe that I need to simplify first then proceed to build the truth table? Work so...
  9. I

    Simplifying an integral expression involving Airy functions

    Hello, Is there some way to express the following integral in terms of some simpler functions? f(x,s) = \int^{\infty}_{-\infty} dk\, e^{-ks} \text{Ai}(-k) \text{Ai}(x-k) where the parameter s \in (0,1) and the coordinate x \in (-\infty,+\infty) The best I can come up with is to...
  10. B

    Expression of electrostatic field

    Homework Statement Why does this expression, given in cylindrical coordinates, rapresent an electrostatic field: $${\bf E(r)}=\frac{\alpha}{z^2}{\bf u_r}-2 \frac{\alpha r}{z^3}{\bf u_z} $$ Homework Equations The Attempt at a Solution I can't understand why the expression rapresent...
  11. Drakkith

    How to Simplify the Expression (6w2-w-3) + (7w2-4w+5)

    Homework Statement Simplify, if possible. (6w2-w-3) + (7w2-4w+5) Homework Equations The Attempt at a Solution I attempted to factor both expressions, but they don't seem to be factorable. Is this already simplified as much as possible, or am I missing something?
  12. Petrus

    MHB What is the expression for |c_n| in terms of the given matrice?

    Matrice c_n is a 2nxn2 matrice and is given by (\delta_{ij}+2\delta_{i,2n-j+1})_{ij} determine the expression of |c_n| progress: I have been drawing the matrice n=1,2,3 and calculate the determinant. As you see there is a pattern with the matrice and I would like to have tips how i write |c_n|...
  13. B

    MHB Simplify a trig. expression using a right triangle

    I have the expression sin^{-1}(cosx) I'm not sure how to simplify this at all. I've never done a problem like this and it's in my textbook as a review question. A quick boot in the right direction would help
  14. M

    I hope this helps!Translating Statements into Logical Formulas

    Is the statement "if you are a comedian then you are funny." equivalent to what is defined in part (a)?
  15. S

    MHB Solving Complex Expressions for Scientists

    How to go about solving this one? (1-i)-1+i so far i have tries using the famous Uv=ev(ln(U) im stuck where i get e-1/2ln(2)+(pi/4)-2kpi*ei(-1/2ln(2)+(pi/4)-2kpi)
  16. S

    MHB Evaluating imaginary expression

    Find all possible Values of: 2(-i)
  17. M

    How do I simplify (sin t + cos t)2 / sin t cos t?

    Homework Statement Simplify: (sin t + cos t)2 / sin t cos t Homework Equations tan t = sin t/cos t cot t = cos t/sin t cot t = 1/tan t The Attempt at a Solution (sin t + cos t)2 / sin t cos tsin2 t + 2sin t cos t + cos2 t / sin t cos t(sin t/cos t) + 2 + (cos t/sin t) tan t + cot t + 2...
  18. M

    Simplifying a trigonometry expression

    Homework Statement Simplify: [(sec x)(sec2 x) - (tan x - 1)(sec x tan x)] / sec2 x Homework Equations none The Attempt at a Solution [(sec x)(sec2 x) - (tan x - 1)(sec x tan x)] / sec2 x [(sec x)(sec2 x) - tan x (1 -1) sec x ] / sec2 x [(sec x)(sec2 x) - 0 ] /...
  19. C

    Eliminate the denominator in this expression

    Homework Statement Eliminate the denominator on the RHS of the following expression sin(\alpha)-sin(\beta) = -\frac{-v(sin(\alpha) cos(\alpha) + sin(\alpha) cos(\beta)}{c-vcos(\alpha)} and from it, derive sin(\alpha)-sin(\beta) = -\frac{v}{c}(sin(\alpha)cos(\beta)+sin(\beta)cos(\alpha))...
  20. A

    Why is this expression bounded by 1?

    How exactly might one go about showing that \left| \frac{1 - e^{-iy}}{-iy} \right| is bounded by 1 for y\in \mathbb R? I thought this would be easy to show using the series expansion of e^{-iy} in some way: \left| \frac{1 - e^{-iy}}{-iy} \right| = \left| 1 - \frac{iy}{2} -...
  21. S

    Inverse Laplace Transform of this expression?

    Homework Statement Find the Inverse Laplace Transform of \frac{1}{(s^{2} + 1)^{2}} Homework Equations The Attempt at a Solution I tried using partial fractions but it didn't work. It looks like a cosine transform, but I don't know what else to do. Help please :(
  22. C

    Find an Expression for the Helmholtz free energy

    Homework Statement I am attempting the problem below, I might have the correct answer but would appreciate if someone could confirm this (or tell me where I'm going wrong). Consider a statement having 2 states, one at energy 0 and one at energy ε. Find an expression for the Helmholtz free...
  23. anemone

    MHB Find the Units Digit of An Expression

    What is the units digit of \left\lfloor \frac{10^{20000}}{10^{100}+3} \right\rfloor?
  24. alyafey22

    MHB Creating a Summation Expression with k and m Variables

    How to write something similar to the following Or is it better to write \sum_{n=k ,m=1}^{k+1}
  25. D

    MATLAB A simple symbolic expression in Matlab

    I tried to check x²-1 = (x+1)(x--1) So I did the following: Matlab returns 0. Any suggestions? :) (Matlab beginner by the way)
  26. K

    Simple algebra/trig expression, simplifying

    Hello, I'm trying to solve this equation. (4-4cos(∏*0.16*4)) - (4-4cos(∏*0.16*3)) It seems like it should be so easy. First I start with the left hand side (∏*0.16*4). Then I take the cosine of that, and then multiply it by 4. Then I do 4 - [answer] to get a value for the full left side...
  27. S

    MHB How can I confidently find the value of z in the given equation?

    Find the value of z = \frac 1{\cos x} + \tan x given \frac 1{\cos x} - \tan x = 2. By squaring and using trigonometric identities on the given equation, one can arrive at \frac {1- \sin x}{1 + \sin x} = 4 The unknown expression z can, by squaring, be written as z^2 = \frac {1 + \sin x}{1 -...
  28. anemone

    MHB Evaluate Trigonometric Expression Challenge

    Evaluate \tan\frac{\pi}{13}\tan\frac{2\pi}{13}\tan\frac{3 \pi}{13}\tan\frac{4\pi}{13}\tan\frac{5\pi}{13} \tan \frac{6\pi}{13}.
  29. N

    How to simplify following trignometric expression

    Homework Statement - 1/[cosx(cos(x-90))] The Attempt at a Solution = - 1/[cosx(-cos(90-x))] //so first I take the negative sign out from (x-90) to make it (90-x) = +1/[cosx(cos(90-x))] // negative sign from outside the cos and outside the entire fraction combine to...
  30. V

    Calculating an expression for trace of generators of two Lie algebra

    Suppose we have $$[Q^a,Q^b]=if^c_{ab}Q^c$$ where Q's are generators of a Lie algebra associated a SU(N) group. So Q's are traceless. Also we have $$[P^a,P^b]=0$$ where P's are generators of a Lie algebra associated to an Abelian group. We have the following relation between these generators...
  31. Saitama

    Simplifying a trigonometric expression

    Homework Statement If ##\displaystyle \tan\left(\frac{\pi}{4}+\frac{y}{2}\right)=\tan^3\left( \frac{\pi}{4}+\frac {x}{2} \right)##, prove that $$\frac{\sin y}{\sin x}=\frac{3+\sin^2 x}{1+3\sin^2x}$$Homework Equations The Attempt at a Solution...
  32. QuantumCurt

    Find the exact value of the trigonometric expression

    Homework Statement Find the exact value, without using a calculator. \ cos(\frac{\pi}{15}) \ cos(\frac{\pi}{45}) The Attempt at a Solution I started off using a product to sum formula- \frac{1}{2}[cos(\frac{4\pi}{45})+ \ cos(\frac{2\pi}{45})] Now I don't know where to...
  33. E

    Equivalent form for Binomial Expression?

    Is there a way to express ##{n\choose k}{n\choose r}## in another form without n as the "top" of the binomial coefficient? I remember seeing it once but I forgot what it was.
  34. paulmdrdo1

    MHB Simplification of Expression

    how would you simplify this $\displaystyle \frac{1}{5}\ln|\sin5x|+\frac{1}{5}\ln|\csc5x-\cot5x|$ please explain.
  35. anemone

    MHB Evaluating Trigonometric Expression

    Without the use of a calculator, evaluate \tan^2 20^{\circ}+\tan^2 40^{\circ}+\tan^2 80^{\circ}.
  36. Saitama

    What is the Range of the Given Expression When ##\sin 2\beta≠0##?

    Homework Statement If ##\beta## is such that ##\sin 2\beta≠0##, then show that the expression ##\displaystyle \frac{x^2+2x\cos\alpha+1}{x^2+2x\cos\beta+1}## (x real) always lies between ##\cos^2\alpha/\cos^2\beta## and ##\sin^2\alpha/\sin^2\beta##. Homework Equations The Attempt at...
  37. L

    Find the Expression of an Electric Field Produced by a Dipole

    Homework Statement An electric dipole is located along the y-axis as shown in (picture attached). The magnitude of its electric dipole moment is defined as p=2aq. (a) At a point P, which is far from the dipole (r>>a), show that the electric potential is V=\frac{k_{e}pcosθ}{r^{2}} (b)...
  38. Q

    Calculating an expression for work in a magnetic field

    As shown, I must derive a formula to find work. http://i.imgur.com/0U0eLqm.jpg I proceeded as follows. W= F * D = (B * I * L) * D V = BA/T I = V/R = (BA/t)/R = BA/tR F = B * (BA/tR) * A W = ((B^2*A^2)/tR) * A W = (B^2 * A^3)/tR Does that seem right? IIRC, the B*I*L formula is only...
  39. V

    Calculating the residue of complicated expression

    Homework Statement Hi, I want to calculate the residue of this expression: Homework Equations I know that the residue of a function with a pole of k-th order is given by this: The Attempt at a Solution I know that the function has infinite number of poles at k*∏, for k=-∞ to...
  40. B

    Deriving the expression for wind velocity around low pressure area

    Hi Can somebody tell me the steps and assumptions made in deriving the equation to calculate the wind velocity around a low pressure area ? (see the attachment fro Kleppner & Kolenkow). I tried to derive like this : Coordinate system located on Earth's surface with i direction towards E, j...
  41. N

    Mathematica Mathematica: Recursive expression

    Hi I am trying to find a smart way to write the following fraction, $$ F = \frac{a_1}{1+\frac{a_2}{1+\frac{a_3}{1+a_4}}} $$ Here we can just take a_n= n for simplicity. My fraction is in principle infinite, but I am trying to construct a function which can find F for a given n recursively. I...
  42. U

    Find the maximum value of this expression

    Homework Statement \dfrac{tan\left( \theta + 2\pi /3 \right) - tan\left( \theta + \pi /6 \right) + cos\left( \theta + \pi /6 \right)}{\sqrt{3}} \\ \theta \in \left( -5 \pi /12, - \pi /3 \right) The Attempt at a Solution At maximum, f'(x)=0 sin(θ+∏/6)=0 But there is no theta in...
  43. Sudharaka

    MHB Simplifying an Expression (Heather Jean's Question from Facebook)

    Heather Jean's of Facebook writes: Simplify, \[-(6y-\gamma)-5(-\gamma+6y)\]
  44. N

    Canonical expression and truth table

    Hey, What are the steps to follow to draw a truth table and create canonical expression from a given expression A? Lets say I have A= B'.(C'+D) 1) first I have to draw the truth table for the expression above, but How could I do that since I only have one expression? 2)Then I...
  45. Femme_physics

    Rewriting an expression what math operation did my teacher do?

    Rewriting an expression...what math operation did my teacher do? I'm trying to see how did my teacher rewrite this expression in the following manner: What mathametical operation did he do? I really can't see it...
  46. Femme_physics

    How can I simplify this expression without getting confused?

    My basic math is failing me again :( My attempt to simply: My teacher's attempt: Ignore the difference in notation. He writes || which signifies (A x B) / (A + B) = A || B And yes I'm aware there is more to simplify but I fail to follow him on the first step
  47. J

    Writing Common Ion Concentration in Buffer Eq. Expression

    Homework Statement What is the pH of a buffer solution created by combining 100 mL of 0.2 M acetic acid and 400 mL of 0.10 M sodium acetate? Ka= 1.8 x 10^(-5)Homework Equations 1.8 x 10-5=([C2H3O2-][H+])/([HC2H3O2]) The Attempt at a Solution I know what I'm supposed to do to solve this...
  48. P

    Simplify Expression and Find Product of a*b + 15m + 11n + 8

    for which value of a the expression write a*m*b+15*m+11*n+8 can be written into a product of something(with m)*something (with n) i can think how to find the product of this expression
  49. I

    How to evaluate this nabla expression in spherical coordinates?

    I'm currently working out the Schrödinger equation for a proton in a constant magnetic field for a research project, and while computing the Hamiltonian I came across this expression: (\vec{A}\cdot\nabla)\Psi where \Psi is a scalar function of r, theta, and phi. How do you evaluate this...
  50. G

    Reduction of Boolean Expression to its Lowest From

    Hey Guys I am Currently doing my degree in information systems. At the moment the subject is PLC(Processing and Logic Concepts) I understand all of it, I am not sertain on how to start reducing a boolean expression. Once the first step is done I normally get it and can complete the...
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