Study Guides (248,609)
Canada (121,634)
Biology (1,536)

Genetics Lecture No. 16.docx

4 Pages

Course Code
Biology 2581B
Jim Karagiannis

This preview shows page 1. Sign up to view the full 4 pages of the document.
Genetics Lecture No. 16: Quantitating Gene Regulation th Monday March 11 , 2013 Introduction: -So far, we have examined gene regulation in a strictly qualitative manner (e.g. the transcriptional levels of the lac operon were either high or low; the presence of glucose in the growth media decreased transcription of the lac operon). Is it possible to examine the transcription of genes in a quantitative manner? If so what could this tell us about transcriptional regulatory networks? Quantitating Gene Regulation: -The goal of quantitating gene regulation is to create working mathematical models of two very simple genetic networks. Here is a model we can use for a given gene Y: Activation: Repression: X -> (+) Y X -> (-) Y X = activator X = repressor Y = target gene Y = target gene -Using this model, we can quantify the rate of mRNA production and degradation for gene Y using a “source and sink” model: Source Sink The Y mRNA is being accumulated in box Y in nmoles: dY/dt = b - aY 1) When production rate > degradation rate, accumulation of Y mRNA in the box. 2) When production rate < degradation rate, loss of Y mRNA in the box. 3) When production rate = degradation rate, levels of Y mRNA stay the same. The level of Y mRNA is dependent on two things: 1) How much Y mRNA is produced through transcription of the source (rate of production) 2) How much Y mRNA is degraded through degradation by nucleases (rate of degradation) Spigots (a and b) control the flow of Y mRNA into the box: 1) When spigot b is open, there is a high production rate of Y mRNA (in nmoles/min) 2) When spigot a is open, there is a high degradation rate of Y mRNA (1/min) Degradation rate depends on the amount of Y mRNA that is present: • If a = 0.1/min, 10% of Y mRNA is degraded every minute • If at an instant in time, there are 1000 nmoles, the rate of degradation is 100 nmol/min • If at another instant in time, there are 100 nmoles, the rate of degradation is 10 nmol/min • a = 10 nmoles / min x 100 nmole = 0.1/min Simulating Gene Transcription: -The transcription of a gene can be simulated with the help of specialized computer programs. For example, it is possible to “create” a gene that is transcribed with a given production and degradation rate within a computer program. In this way, the computer can handle the calculations and you can focus on the results. The levels of Y mRNA will reach a steady state level within a cell based solely on production and degradation rates (in order to quantitate the amount of Y mRNA, you need to know production Steady State Level: Gene F: b = 10 nmoles/min; a = 0.1/min; Yinit and degradation -A concentration of Y mRNA reached over time rates): where the rate of change is zero; calculated by dividing dY/dt = b – a Y the production rate by the degradation rate of the gene. 0 = b – a Y st Gene G: b = 5 nmoles/min; a = 0.1/min; Y init [Y mRNA] (nmol) -b = -a Y st Gene H: b = 5 nmoles/min; a = 0.2/min; Y = 0 init Y stb / a Time (min) The initial levels of Y mRNA will not affect the final steady state levels of the message Gene F: b = 10 nmoles/min; a = 0.1/min
More Less
Unlock Document

Only page 1 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.