Interesting Cancer Discovery

For once I'm not actually posting one of my own articles! Read about this today and thought it was really interesting - a modified form of the herpes virus has been used to treat skin cancers. As I did my Extended Project Qualification (EPQ) on the use of cannabinoids (extracts from the cannabis plant) to treat cancer, I find novel methods of tackling tumours really fascinating. Worth a read if you have a minute, I've used the NHS' coverage of it as I feel it's laid out more clearly than some of the others!

http://www.nhs.uk/news/2015/05May/Pages/Modified-herpes-virus-could-combat-skin-cancer.aspx

Introduction to DNA, Genes, Chromosomes and Nucleotides

Genetics can seem a little daunting at first but once the basics are understood it is fairly easy to build on that knowledge and understand genetics in much more depth. To begin with, we need to establish the definitions of some key terms.

Probably the best place to start is with nucleotides, which are the building blocks of DNA.
They consist of a sugar (called deoxyribose), a base (a nitrogenous ring-like structure), and a phosphate group (pictured left).

The sugar and the phosphate groups are pretty much always the same in DNA nucleotides, but it is the bases that are really important. There are four different types of bases, known as adenine, thymine, cytosine and guanine. 

DNA stands for Deoxyribonucleic Acid and is actually just long strings of nucleotides. It carries the genetic material for the cell and is located in the nucleus (which acts as the cell's 'brain'). Its structure is a bit like a twisted ladder and is known as the "DNA double helix", with two strands of nucleotides opposite each other.The nucleotides' sugars and phosphates form the blue and red strands, and bonded bases form the 'rungs' of the ladder, as pictured to the right. 

The bases mentioned earlier (adenine, thymine, cytosine and guanine) pair in particular ways in the DNA molecule:

Adenine ALWAYS pairs with thymine 

Cytosine ALWAYS pairs with guanine. 

This is also shown here, represented by the letters A, T, C and G. 

A gene is a length of DNA that codes for a particular protein. Proteins are made up of amino acids that form long chains called polypeptides - large polypeptides are referred to as proteins. One amino acid is formed from 3 nucleotides which are referred to as a 'triplet code'. A series of triplet codes forms a series of amino acids. Humans have about 25,000 genes, made up of about 3 billion nucleotide base pairs. The difference between DNA and genes is that DNA is all of the genetic information in the cell, and the gene is just one particular segment of this that has a specific code for a specific protein. 

DNA is not just free in the nucleus but is in fact organised into chromosomes. The genes are on these chromosomes - different genes are present on different chromosomes. Humans have 23 pairs of chromosomes (one copy of each chromosome from each parent). Chromosomes are made up of 'chromatin' which is just DNA wrapped around histone proteins. 'Chromosome' is the collective term for two sister chromatids (as mentioned before, one comes from each parent) joined in the middle by the 'centromere' which will be explored further when I discuss mitosis and meiosis. 

SO, just to clarify:

- The nucleus stores all of the cell's genetic material. 

- In the nucleus, there are chromosomes which are comprised of DNA tightly coiled around special proteins. 

- DNA is made from chains of nucleotides.

- Sections of the DNA that code for particular proteins are referred to as genes. 

Article 3: Seasonal Variation in Genetic Immunity

Wrote my third article for Bang this week and currently in the process of writing my first article for the Oxford Student which is exciting! I also went to an excellent talk by Immediate Media tonight, really hoping I can do work experience with them at some point. Anyway, link to the article is below (yet another one on genetics sorry) and will be hopefully posting more often in the next few weeks!

http://www.bangscience.org/2015/05/immunity-and-the-genetic-seasons-gene-function-varies-throughout-the-year/

Key Texts for Genetics

Below is a list of the main books I have found most helpful for my studies, from hardest to easiest (so choose the level you think is most appropriate to your current understanding if you are interested in reading around the subject further).

1) Hartwell, L., 2008. Genetics: From Genes to Genomes. 3rd ed. New York: McGraw-Hill.

This book is very challenging in some places and is definitely not for someone who is just dabbling in genetics as there are much simpler books out there!

2) Griffiths, A., 2005. Introduction to Genetic Analysis. Basingstoke: W.H. Freeman and Company.

Whilst aimed at around the same level as book 1 in terms of content, I found this book was much better at explaining most of the topics and I also much preferred the layout, but this may just be personal preference.

3) Sudbery, P., 2002. Human Molecular Genetics. 2nd ed. Harlow: Pearson Education Ltd.

This book is much less of a textbook-style than 1 and 2 and is therefore much thinner and generally smaller, so seems less daunting and for the most part explains things well. However, in terms of breadth of topics, it doesn't cover nearly as much and focuses on genetic diseases and aspects of genetics specific to just humans so is not as good of an overview.

4) Fletcher, H., Hickey, I., 2013. Genetics. 4^th ed. Garland Science, Taylor and Francis Group, LLC.

In my opinion, this is the best book by far in terms of balance between complexity and how easy it is to understand. Again, this is probably best for those with a basic level of genetics knowledge but it explains everything really really well and covers nearly every topic you are likely to need.

5) Rodden Robinson, T., 2011. Genetics for Dummies. John Wiley & Sons.

Similar to book 4, this goes into slightly less complexity but I feel is not as well presented as 4. However, a great book for beginners.

6) Hocking, S., 2008. OCR A2 Biology Student Book. s.l.:Heinemann.

Although this is an A-level book, the genetics section is brilliant for those just starting out as a basic backdrop of the main concepts of genetics, or as a refresher for those who haven't studied genetics for a while.