expression

Examples of expression in the following topics:

• Simplifying Exponential Expressions

  • Multiplying exponential expressions with the same base: $a^m \cdot a^n = a^{m+n}$
  • Previously, we have applied these rules only to expressions involving integers.
  • The same rule applies to expressions with variables.
  • Now apply the rule for dividing exponential expressions with the same base:
  • To simplify the first part of the expression, apply the rule for multiplying two exponential expressions with the same base:

• Expressing the Equilibrium Constant of a Gas in Terms of Pressure

  • Note that this expression is extremely similar to KC, the equilibrium expression written in terms of concentrations.
  • In order to prevent confusion, do not use brackets ([ ]), when writing KP expressions.
  • Therefore, the term RT is a constant in the above expression.
  • In this expression, $\Delta n$ is a measure of the change in number of moles of gas in the reaction.
  • Write the equilibrium expression, KP, in terms of the partial pressures of a gas-phase reaction

• Mammalian Gene Expression in Bacteria

  • In the broadest sense, mammalian gene expression includes every living cell but the term is more normally used to refer to expression as a laboratory tool.
  • An expression system is therefore often artificial in some manner.
  • Viruses and bacteria are an excellent example of expression systems.
  • The oldest and most widely used expression systems are cell-based.
  • There are many ways to introduce foreign DNA to a cell for expression, and there are many different host cells which may be used for expression.

• Rational Action in Specific Contexts

  • Our basic expression for the elements of action and decision is not merely manipulatable.
  • In the context of the transformations, the original expression also acquires a special meaning which is distinguishable from its role as a general model.
  • The six variations of the expression (again taking the circumstances of action as implicit) are (shown in Table 2):
  • Each of these six variations can be manipulated in exactly the same ways as the basic expressions, but we need
  • Each of these six variations can be manipulated in exactly the same ways as the basic expressions, but we need not go into this here.

• The Process and Purpose of Gene Expression Regulation

  • Therefore, only a small subset of proteins is expressed in a cell that constitutes its proteome.
  • Specialized proteins that make up the eye (iris, lens, and cornea) are only expressed in the eye, whereas the specialized proteins in the heart (pacemaker cells, heart muscle, and valves) are only expressed in the heart.
  • The expression of specific genes is a highly-regulated process with many levels and stages of control.
  • This complexity ensures the proper expression in the proper cell at the proper time.
  • In this section, you will learn about the various methods of gene regulation and the mechanisms used to control gene expression, such as: epigenetic, transcriptional, post-transcriptional, translational, and post-translational controls in eukaryotic gene expression, and transcriptional control in prokaryotic gene expression.

• Simplifying, Multiplying, and Dividing Rational Expressions

  • Performing these operations on rational expressions often involves factoring polynomial expressions out of the numerator and denominator.
  • As a first example, consider the rational expression $\frac { 3x^3 }{ x }$.
  • We follow the same rules to multiply two rational expressions together.
  • Dividing rational expressions follows the same rules as dividing fractions.
  • The same applies to dividing rational expressions; the first expression is multiplied by the reciprocal of the second.

• Riboswitches

  • Riboswitches are naturally occurring RNA molecules that can regulate gene expression.
  • Riboswitches are specific components of an mRNA molecule that regulates gene expression.
  • An mRNA molecule may contain a riboswitch that directly regulates its own expression.
  • The binding of the aptamer to the target molecule results in a conformational change of the expression platform, thus affecting gene expression.
  • The expression platforms, which control gene expression, can either be turned off or activated depending on the specific function of the small molecule.

• Simplifying Radical Expressions

  • A radical expression that contains variables can often be simplified to a more basic expression, much as can expressions involving only integers.
  • Expressions that include roots are known as radical expressions.
  • A radical expression is said to be in simplified form if:
  • For the purposes of simplification, radical expressions containing variables are treated no differently from expressions containing integers.
  • This follows the same logic that we used above, when simplifying the radical expression with integers:

• Adding and Subtracting Algebraic Expressions

  • Every algebraic expression is made up of one or more terms. 
  • Terms in these expressions are separated by the operators $+$ or $-$.
  • For instance, in the expression $x + 5$, there are two terms; in the expression $2x^2$, there is only one term.
  • The same rules apply when an expression involves subtraction.
  • The expression therefore simplifies to:

• Plasmids as Cloning Vectors

  • Vectors called expression vectors (expression constructs) express the transgene in the target cell, and they generally have a promoter sequence that drives expression of the transgene.
  • However, expression vectors have a two expression patterns: constitutive (consistent expression) or inducible (expression only under certain conditions or chemicals).
  • The above conditions are necessary for expression vectors in eukaryotes, not prokaryotes.
  • Allows for antibody identification of cells expressing the target protein.
  • Protein purification tags: Some expression vectors include proteins or peptide sequences that allows for easier purification of the expressed protein.