Life Sciences lab classes explained

So once you have isolated genomic DNA from some peas, you need a way to assess how much DNA you have got, and how pure you have managed to get it.... This can be done using a   spectrophotometer  taking advantage of the different absorbance spectrums of DNA and the common contaminants, RNA and proteins. As I have shown in the diagram of an absorbance spectrum below,  DNA  absorbs light most at a wavelength of  260nm ,  protein  absorbs light most at   280nm .  A   DNA/Protein mixture  on the other hand will have a spectrum  somewhere in-between  -  exactly where this spectrum will be depend on how much DNA vs protein there is in the sample. So when we are assessing how much DNA we have, the absorbance of the sample at 260nm can be used to estimate this.  And when we are assessing the purity of the sample (i.e. how much protein contamination we have), we can find the ratio of the absorbance of ...

In practical 9 you will be isolating the DNA from peas - this might seem like a long drawn out process, and you might not really know what you are doing.... so here are the steps explained :) I hope that helps you understand what you are doing in the lab! 

You are also going to need to know about Mendel's second law....so here is a heads up: Mendel's Second Law: The Law of Independent Assortment This law is about the inheritance of more than one trait i.e. more than one set of gene pairs/alleles... During gamete formation,  alleles for one trait will separate into the gametes  independently of alleles for another trait. In other words, the way one pair of genes segregates into the gametes is not affected by the way a different pair of genes segregates into the gametes. This means that the inheritance of one trait is not dependent on the inheritance of another. Take a look at this Punnett Square: image taken from: http://course1.winona.edu/sberg/241f07/Lec-note/Mendel.htm The Punnett Square above shows the possible genotype and phenotype of pea plants with respect to their pea colour and pod colour. Here is a description of what this Punnett Square shows: ...

You won't get too far in your fly experiment if you don't know about  Mendel's laws . These laws describe the  fundamental principles of inheritance . Amazingly, Mendel figured this all out by studying pea plants (over 10,000 for 10 years) way before DNA and Genes were understood.  Mendel first reported these laws in 1865 but they faded into obscurity until they were rediscovered in 1900. A couple of definitions: GENOTYPE  =  What genes a cell contains PHENOTYPE  = T he characteristics/traits of an organism  Anyway, that is enough preamble --> to the laws.... Mendel's First Law: The Law of Segregation   Every individual has a pair of genes (alleles)  for any particular trait.  Each parent passes on only one allele to each of their gametes - by meiosis.  Gametes randomly come together,  hence offspring will have again two alleles for a particular trait,  one from their moth...

In practical 1 this semester you will be setting up crosses with   Drosophila melanogaster , aka the annoying fruit fly! So it is going to be pretty important for you to be able to tell the boys from the girls... Here are some pictures to help you out: This first pic is a diagram comparing the male and female fruit fly - the main things to note are The female is bigger than the male The male has a rounded abdomen The female has a more pointed and elongated abdomen  The dark banding on male abdomen increases towards the back, with the end of the abdomen being totally black The female abdomen has much more uniform stripes  image taken from: http://en.wikipedia.org/wiki/Sex-determination_system And this second pic is a real life picture of a female (on the left) and male (on the right). image taken from: http://www.berkeley.edu/news/media/releases/2002/07/03_paras.html One last thing, if you look reeeally closely, ...