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. anemone

    MHB Simplifying Expression: Simplify Expression

    Simplify the expression $\dfrac{\sqrt{1+\sqrt{1-a^2}}((1+a)\sqrt{1+a}-(1-a)\sqrt{1-a})}{a(2+\sqrt{1-a^2})}$.
  2. D

    Engineering Eq. Logic Expression for Circuit 2

    Homework Statement https://www.dropbox.com/s/d3qdr96n27j8wa7/circuit.png?dl=0 The questions is as follows: For each circuit write the equivalent logic expression. Homework Equations (B' + C) * A (?) My Attempt at circuit 2 (A* (A' * C') * B') + (A * C * B) My Attempt at Circuit 1 The Attempt...
  3. H

    Derive an expression for the potential

    Homework Statement A positive charge +q is located at the point x= 0, y = -a and a negative charge -q is located at the point x=0, y=a (a) Derive an expression for the potential at points on the y-axis as a function of the coordinate y. Take V to be zero at an infinite distance from the...
  4. D

    MHB Deriving a Vector Expression from Given Direction

    How can you derive an expression from the given direction defined by dx=2dy=-2dz. This is just a part of a problem that I'am solving. I have no idea how to get a vector expression using the given info. please help. Thanks! by the way I'm trying to find the directional derivative of a certain...
  5. R

    Finding the sum of inverse trigonometric expression

    Homework Statement Find ## \sum_1^{23} tan^{-1}(\frac{1}{n^2+n+1}) ## Homework Equations ## tan^{-1}x + tan^{-1}y = tan^{-1}(\frac{x+y}{1-xy} )##The Attempt at a Solution I think we have to split the question in a form of relevant equation given above. First thing what should I do?
  6. L

    Function expression, area of a window

    Homework Statement http://www.inter-ped.no/skei/MAT1013%20Matematikk%201T%20%20bokmal.pdf Page 10 task 4 for a picture. The window above consists of a rectangle and a semicircle. The windows perimeter is 8.0m. What does the radius in the semicircle have to be for the area of the window to be...
  7. P

    How to simplify the expression -- Boolean algebra

    1. prove that: X'Y'Z + X'YZ' + XY'Z' + XYZ = (X⊕Y)⊕Z Homework Equations Use postulates and theorems. The Attempt at a Solution X'Y'Z + X'YZ' + XY'Z' + XYZ (original expression) X'Y'Z + X'YZ' + X(Y'Z' + YZ) (distributive) X'Y'Z + X'YZ' + X.1 (complement) X'Y'Z + X'YZ' + X (identity)[/B]...
  8. A

    Finding the expression for momentum.

    Homework Statement A bullet of mass m is fired into a block of mass M that is at rest. The block, with the bullet embedded, slides distance d across a horizontal surface. The coefficient of kinetic friction is μk. Find an expression for the bullet's speed vbullet. Express your answer in terms...
  9. Telemachus

    Feynman Expression for the field of a point charge

    Hi there. I'm reading Jackson's Classical Electrodynamics. 1. Homework Statement In chapter 6, the equation for the electric field of a moving point charge is derived. I could follow the mathematics to get the electric field for the moving charge, which is given in equation 6.57 in Jackson...
  10. U

    Quick expression on geodesic equation

    Taken from Hobson's book: How did they get this form? \dot u^{\mu} = - \Gamma_{v\sigma}^\mu u^v u^\sigma \dot u^{\mu} g_{\mu \beta} \delta_\mu ^\beta = - g_{\mu \beta} \delta_\mu ^\beta \Gamma_{v\sigma}^\mu u^v u^\sigma \dot u_{\mu} = - \frac{1}{2} g_{\mu \beta} \delta_\mu ^\beta...
  11. B

    Engineering Finding the steady state expression of a circuit

    Homework Statement For the circuit in (Figure 1) , suppose va=10cos16,000tV vb=20cos4000tV. Suppose that R = 700Ω . Write the steady-state expression for io(t) as io=I′ocos(ω′t+ϕ′)+I′′ocos(ω′′t+ϕ′′), where −180∘<ϕ′≤180∘, −180∘<ϕ′′≤180∘, and ω′>ω′′. Find the numerical value of I′o. Find the...
  12. anemone

    MHB Simplifying Expression: $\frac{z^2(w-x)(x-y)}{(w-x)(x-y)(y-w)}$

    Simplify the expression below: $\dfrac{w^2(z-x)(z-y)}{(w-x)(w-y)}+\dfrac{x^2(z-y)(z-w)}{(x-y)(x-w)}+\dfrac{y^2(z-w)(z-x)}{(y-w)(y-x)}$
  13. STEMucator

    Fixing hazards in a logic expression

    Homework Statement Identify and fix all hazards in ##f = (ab + \bar{a}c)(c + \bar{b}) + ab##. Re-check if the final expression obtained is hazard free. Homework EquationsThe Attempt at a Solution So I used a binary tree and found a static 1 hazard present for ##bc = 11##. The hazard was ##a...
  14. M

    MHB Convert an automaton into a regular expression

    Hey! :o How can we find the regular expression of a language given by an automaton M?? Could you give some hints?? (Wondering) Which are the steps that we have to follow so that we convert an automaton into a regular expression?? (Wondering)
  15. M

    MHB Convert the regular expression to a NFA

    Hey! :o I have to convert the following regular expressions to a NFA: $$(0 \cup 1)^{\star} 000 (0 \cup 1)^{\star}$$ $$(((00)^{\star} (11)) \cup 01)^{\star}$$ $$\emptyset^{\star}$$ $$a(abb)^{\star} \cup b$$ $$a^+ \cup (ab)^{\star}$$ $$(a \cup b^+)a^+b^+$$ For the regular...
  16. U

    Simple expression for Coloumb energy

    How did they arrive at this expression? I understand the ##Q^2## term in the nominator and the ##r = r_0 (A)^{\frac{1}{3}}## term in the denominator. Where did the ##\frac{\alpha}{2}## term come from? Putting in Z=40, A=100 gives ##3.3 \times 10^{14} J##, not ##65 MeV##. The energy term...
  17. anemone

    MHB Simplify a trigonometric expression

    Simplify $\left(\sqrt{3}\sec \dfrac{\pi}{5}+\tan\dfrac{2\pi}{5}\right)\tan \dfrac{2\pi}{15}$.
  18. B

    How Do You Simplify Complex Algebraic Expressions?

    Homework Statement I have the expression [((1-x)/x) * x^(2/1-x)] / x^(2x/1-x) I want to simplify this expression.Homework Equations None The Attempt at a Solution I am not so good with algebra. But I tried to find a common factor for x^(2/1-x)] / (x^2x)/1-x and then add them. However, it...
  19. anemone

    MHB Find closed form expression for a given sum

    Find a closed form expression for \sum_{k=1}^{n^2}\dfrac{n-\lfloor\sqrt{k-1}\rfloor}{\sqrt{k}+\sqrt{k+1}}.
  20. I

    What does this mathematical expression mean physically?

    This is from from Sakurai and Napolitano HW Prob #2.6. I've done the HW problem and can fit all the pieces together with the mathematical formalism, but even afterwards I'm still scratching my head wondering what I'm looking at. I start with the commutator [[H,x],x]. If I take...
  21. R

    Flux through a Disk: What's Wrong with My Method?

    Homework Statement According to my textbook, the electric flux through a disk of radius R situated at a height d from the xy plane is given by: ##2 \pi k_0 Q [1- \frac{d}{\sqrt{R^2+d^2}}]## Where ##k_0 = \frac{1}{4\pi \epsilon_0}## I'm having some difficulty obtaining this answer. Homework...
  22. T

    Rewrite the trigonometric expression as an algebraic equation

    What is this asking for? Is it asking for the trig expression in the form of x and y? Or is it asking for something else?
  23. L

    MHB Can someone help me find the derivative of y=$\sqrt{x+\sqrt{x+\sqrt{x}}}$?

    Hi, this is my online homework exercise. I think I did it right, but the system gives me wrong answer... Can someone please check what I did y=$\sqrt{x+\sqrt{x+\sqrt{x}}}$...
  24. B

    DOUBLE cannot convert the input expression into double array

    Hi Folks, I have a symbolic A=18*1*18 array containing symbols/expressions. I want to populate certain entries of this array into another matrix. For example K(1,1)=A(1,1,1) I get the following ? The following error occurred converting from sym to double: Error using ==> mupadmex Error in...
  25. PsychonautQQ

    Alternate expression for definition of an Ideal?

    If A is an additive subgroup of a ring R, A is said to be an ideal if Ra is contained in A for all a in A; that is, if every multiple of an element of A is again in A. Is it true that A is an ideal of R if Ar is contained in A for all r in R? To me it seems like they are equivalent statements...
  26. K

    Can You Simplify a Parallel Adder SOP Expression Using Karnaugh Maps?

    My working: S3 = A S2 = B S1 = C' S0 = D' F = Sum-Minterm(0, 1, 2, 4, 5, 8) (Basically i find when is X smaller then Y) Used Kmap to arrive at A'C' + B'C'D' + A'B'D' Am i correct?
  27. evinda

    MHB Expression isn't shown entirely

    Hello! (Wave) I am writing a text in LATEX and I wrote this: \begin{align*} \epsilon_p(a+b)&=((a+b)\pmod p, (a+b)\pmod{p^2}, (a+b)\pmod{p^3}, \dots )\\ &=(a\pmod p+b\pmod p, a\pmod{p^2}+b\pmod{p^2}, a\pmod{p^3}+ b \pmod{p^3}, \dots) \\ &=(a\pmod p, a\pmod{p^2},a\pmod{p^3}, \dots)+(b\pmod...
  28. C

    Maximal ideal not containing specific expression

    May there exist an integral domain R, with fraction field K, that fulfills the following condition: there exists x\in K, x\not \in R and a maximal ideal \frak m of R{[}x{]}, such that \frak m does not contain x-a for any a\in R ? Motivation : I am trying to prove a difficult result. A way to...
  29. L

    Expression for magnitude of magnetic force

    Homework Statement A particle with charge q moves with velocity v near a long, straight wire which has a current I flowing through it which generates magnetic field B. Give an expression for the magnitude of the force on this particle in terms of q, v = | v | and the magnitude of the magnetic...
  30. Extreme112

    Help with simplifying boolean expression

    < Mentor Note -- thread moved to HH from the technical math forums, so no HH Template is shown > (A+B)&(C+D) + (A+B)&(C+D)' + C (A+B)&(C+D) + (A+B)&(C'&D') + C by deMorgans (A+B)&[(C+D)+(C'&D')] + C by Distributive I'm just wondering if I did anything wrong in this simplification or if it...
  31. M

    Gravitational potential energy: derive expression for energy

    Homework Statement Part A: Derive an expression for the energy needed to launch an object from the surface of Earth to a height h above the surface. Part B: Ignoring Earth's rotation, how much energy is needed to get the same object into orbit at height h? Express your answer in terms of...
  32. shanepitts

    Is a given expression a travelling wave?

    How can one compute and/or tell if a given expression is a traveling wave? I thought of using the characteristic wave equation δ^(2)ψ/δt^(2)=v^(2)δ^(2)ψ/δx^(2). An example of an expression would be ψ(x,t)=A(x-t). Should I partially derive this expression twice with respect to x and then to t...
  33. Eric Fossum

    Find an expression for the electric field(Mastering Physics)

    I just wanted to post a solution for anyone interested. Any notes on how to solve would be nice for others. 1. Homework Statement Mastering Physics (3rd edition) Problem 26.40 The figure (Figure 1) shows a thin rod of length L with total charge Q. Part A) Find an expression for the...
  34. A

    How to decompose the following expression?

    This comes from one of the research papers that I'm reading. The authors decompose Eq. 1 and obtain Eq. 2. After several attempts, I have been fairly unsuccessful at obtaining Eq. 2 from Eq. 1. I have tried using partial fractions decomposition without much success. Any help would be greatly...
  35. T

    Expression for the line element ds^2

    ds2=guvdxudxv Why is the invariance of ds2 as shown above? Why can't it be something like ds2=guudxudxu or ds2=dxudxu ? Isnt it based on Pythagoras theorem? Why must it have 1 u and 1 v instead of just 2 u or 2 v? Forgive me for such dumb question as I just started.
  36. anemone

    MHB Determine the minimum value of an expression

    If $x,\,y,\,z>0$ and $x+y+z=1$, find the minimum of $\left(x+\dfrac{1}{x}\right)^{10}+\left(y+\dfrac{1}{y}\right)^{10}+\left(z+\dfrac{1}{z}\right)^{10}$.
  37. A

    MHB Simplifying a trigonometric expression

    (tg 570* sin 1469) / (ctg 495 * cos 781) = Its in degrees
  38. anemone

    MHB Evaluate a given expression without using a calculator

    Evaluate the expression $(2^{2^{2014}}+1)(2^{2^{2013}}+1)\cdots(2^{2^2}+1)(2^{2^1}+1)(2^{2^0}+1)+1$
  39. Dethrone

    MHB Simplying Summation Expression

    I encountered this expression while trying o express $f(x)=\ln\left({\frac{1+x}{1-x}}\right)$ in terms of a power series: $$\int \left[ \sum_{n=0}^{\infty}(-1)^n x^n + \sum_{n=0}^{\infty}x^n\right] \,dx$$ The book simplifies this expression as $\int \sum_{n=0}^{\infty}2x^{2n} \,dx$ by expanding...
  40. Silicon Waffle

    Gene expression for bigger limbs

    Take for example a fetus of 2 weeks old and a baby of 2 years old. The fetus doesn't show any limbs, skull. How do I know that is a human fetus ? :nb)
  41. Captain1024

    Obtain Expression For Voltage Across Capacitor

    Homework Statement A voltage source given by ##v_s(t)=25cos(2\pi\times10^3t-30^\circ)## is connected to a series RC load. If R = 1MOhm and C = 200pF, obtain an expression for ##v_c(t)##, the voltage across the capacitor. Answer known to be: ##v_c(t)=15.57cos(2\pi\times10^3t-81.5^\circ)##...
  42. D

    Minterms and maxterms of boolean's expression

    i couldn't find the definition of Minterms and maxterms of boolean's expression on the internet nor my book. Can someone explain it? I was given only this in my book, without any explanation.
  43. V

    Rearranging neutrino expression in see-saw maths

    Hello I'm working through the see-saw mechanism. This is currently from the one-generation section. (I haven't got to the three generation workings yet... although I'm guessing I'll come across something very similar in the three generation model) Could someone please tell me if it is correct...
  44. R

    Reducing a mathematical expression

    Hi guys i need your help! How can i reduce this equation: (Nd-Na)*[B*sqrt((Nd-Na)^2) + n^2) - sqrt((Na-Nd)^2) + n^2)] into this: (B-1)*(Nd-Na) + (B+1)*sqrt(Nd-Na)^2) + n^2)? I'm totally depressed, I'm always stocked in sqrt part of the equation: if there's a techniques in dealing this kind...
  45. P

    MHB Rational Expression word problem

    Nancy's lawn care specializes in residential lawn cutting and fertilizing. Nancy the owner has tracked her income and expenses. She has determined that her profit can be represented by the expression $5A, where A is the area of the lawn in square metres. The time in hours that it takes her to...
  46. anemone

    MHB Evaluating an Expression with $k^{101}=1$ and $k\ne1$

    If $k^{101}=1$ and $k\ne1$, evaluate $\dfrac{k^2}{k-1}+\dfrac{k^4}{k^2-1}+\dfrac{k^6}{k^3-1}+\cdots+\dfrac{k^{200}}{k^{100}-1}$.
  47. J

    MHB Range of t in rational expression

    Evaluation of range of real values of $t$ for which $\displaystyle 2\sin t = \frac{1-2x+5x^2}{3x^2-2x-1}\;,$ Where $\displaystyle t\in \left[-\frac{\pi}{2}\;,\frac{\pi}{2}\right]$
  48. 2

    [CalcII/DiffEq] Closed form expression for f(x) which the series converges

    Homework Statement Find a closed form expression for the function f(x) which the power series Σn=0..∞ n(-1)nxn+1 converges to and determine the values of x for which f(x) equals the given power series. Homework Equations N/A The Attempt at a Solution I'm actually not sure how to start. First...
  49. M

    Differentiation of an exponential expression

    Homework Statement [/B] I need to differentiate the exponential function i = 12.5 (1-e^-t/CR) and I need to plot a table so that I can do a graph of i against t but I'm not sure how. (CR is the equivelant of Capacitance 20 Micro Fards and Resistance 300 Kilo Ohms)Homework Equations [/B] How do...
  50. Pythagorean

    "Mind-controlled" gene expression

    Mind-controlled transgene expression by a wireless-powered optogenetic designer cell implant. Kind of a sensationalized title, since it's really just interpreting brain waves through a BCI, but neat anyway. http://www.nature.com/ncomms/2014/141111/ncomms6392/full/ncomms6392.html
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