Life Sciences lab classes explained

Chi squared is the other statistical test you are coming across in your first year.... I have already written  a post on the t-test ,   and how this can be used to see if means from different data sets are significantly different. But the t-test only works with   measurement data   (bummer!) . These are data that are continuously variable - i.e. can take any numerical value within a range, like between 1mm and 2mm you can have any value eg 1.5mm or 1.0000003mm or 1.8585mm......... So what about when you have data that is  discontinuous .  For example eye colour, motile or non-motile cells, Marmite lover or Marmite detester. In these cases we are dealing with numbers of individuals in defined classes - therefore these data can only have particular values with nothing in-between.  In these cases, the questions you might have are;  Do my results reflect what I expected?  or,  Are my results significantly different from what I expected  and so  are they suggesting my expectation

I have found this really excellent U-tube video on the T-test and P-values. It takes you on a really nice slow tour of the T-test and P-values, with some nice visual examples. NB, the main example the guy shows he calls the 'independent samples t-test'. This is also sometimes called the 'two sample t-test'. Also, make sure you watch all the way to the end-  the last thing dealt with is how to write the results of a t-test down - this will be very useful to you for your 109 work!! Enjoy! If the video isn't working, you can find it at :   http://www.youtube.com/watch?v=0Pd3dc1GcHc

The second experiment you will be setting up in your first 107 practical will involve exposing two different yeast strains to hydrogen peroxide - H 2 O 2 . One of the yeast strains will be   wild type .  The other yeast strain will be   mutant .  The  mutant   strain has had three genes involved in DNA repair removed. This means that the   mutant   yeast will be less good at repairing damaged DNA. Since H 2 O 2  produces free radicals that love damaging DNA, you can imagine that your mutated yeast might not grow as well as the wild type yeast when exposed to H 2 O 2 . So far so good. But what if you want to actually measure how much more susceptible the mutant yeast is to the H 2 O 2  than the wild type yeast?  This is where the LD50 comes in.... The  LD50   (aka lethal dose) is how much of something it takes to kill half of a population, or, if you have a more positive mind, at what amount of something half of a population will still survive. So, for our yeast and H 2 O

107 Practical 1 is just around the corner, so here is your trusty summary of what to expect :) Practical 1 is actually split into two halves - you will be setting up  two different experiments   and then you will be collecting and analyzing the results in your next practical session. Experiment 1   will involve our friends the fruit flies (actually, I'm no great fan of these little bugs!). You will be setting up some crosses to investigate Mendel's 1st law of inheritance. Experiment 2   is an ecotoxicology experiment - you will be testing the sensitivity of two strains of the yeast  Saccharomyces cerevisiae  to H 2 O 2 . One of the strains you are testing will have several mutations in its genome and your goal is to test whether these mutations have given the mutant yeast any survival advantage over the wild-type yeast when exposed to the toxin  H 2 O 2 . Here are some of the things this day is going to teach you about: how to set up crosses with fruit flies - 

Hi all, I hope you exams have been going well....semester 2 is almost here  - here is a recap of some of the important points from your 'introduction to semester 2 of Life107' lecture you had at the end of last semester: This semester  LIFE107  is going to be a little different as the focus is going to move from learning good laboratory practice to   Experimental Design and Analysis!   -  sounds scary?   Never fear!  You are not going to be expected to individually design and run an entire experiment from scratch!  Phew!  Rather, you are going to work with your group and you will discuss, plan and do experiments and data analysis together,  PLUS , you will have a friendly demonstrator always at hand ready to help you out if you get stuck! Sound less bad now? NOTE: 1. Your practical sessions will last for the entire day  - so you all should come to your lab at 9am!   2. You will have two experiments this semester, you will be setting up both experiments one week, and t