1 in 10 of global mortality now attributed to smoking and its effects


Despite all the negative publicity, despite all the warnings, despite education on the risks, the number of people who smoke tobacco continues to rise and the mortality from smoking related illnesses now has reached 1 in 10 of all deaths.

This article is from the BBC, 6th March 2017, quoting a report in the Lancet – probably the world’s most respected medical research journal.




IB Past Paper Questions: Carbohydrates, lipids, proteins and nucleic acids (incl. DNA replication)


This is a collection of multiple choice and long answer questions on molecular biology, from old IB papers. Especially for SB. Try to complete at least the MC questions before next Tuesday.


Enjoy dissection? Watch this one, of an Amur tiger

Siberian tigers

The Amur tiger almost became extinct in the 1940’s, with maybe just 40 individuals remaining in the wild. Their conservation and subsequent recovery, supported by WWF, has been slow work but now a population of about 550 exists in the far east of Russia, northern China and perhaps North Korea. They are the tigers with the largest home range of any tiger species – needing to cover huge distances in order to get subsistence from the inhospitable terrain which they inhabit.

A team in Scotland made a dissection of an Amur tiger and carefully recorded and annotated it on video.

Here is the full link to the BBC Earth web page: http://www.bbc.com/earth/story/20170302-discover-how-the-amazing-body-of-an-amur-tiger-works


Gene therapy is successfully used to cure sickle celled anaemia. A first!



2nd March 2017

Here is a link to a BBC summary about the way in which, for the very first time, gene therapy has been used to ‘correct’ the abnormal mutation which causes sickle celled anaemia. A 13 year old French boy with an advanced condition of sickle celled anaemia had bone marrow removed and then genetically modified using a lentivirus vector, before being reintroduced back into his body, where it has subsequently been producing largely faultless red cells. http://www.bbc.com/news/health-39142971

This hugely successful and significant gene therapy procedure  was described formally March 2nd 2017 in the New England Journal of Medicine (NEJM), from where it cannot be freely accessed. A version of the story with much more detail and science than the BBC version can be accessed on the Medscape web pages:  http://www.medscape.com/viewarticle/876505

In the field of gene therapy this procedure is hugely, hugely significant. For some decades now the dream has been that gene therapy will offer ‘wonder’ cures for several genetically inherited diseases but so far, successes have been limited. From the University of Utah’s Genetic Science Learning Center (Learn.Genetics), here is a summary of the more important successes:  http://learn.genetics.utah.edu/content/genetherapy/success/

(Let me plug, yet again, the University of Utah’s Genetic Science Learning Center. A fabulous resource!  http://learn.genetics.utah.edu/)

Check out Topic 3.1 Genes, on this Blog, to learn more about sickle celled anaemia:  https://johnosborneabcbiology.wordpress.com/genetics-topics-3-10/3-1-genes/


Drunken Monkey Hypothesis: some serious evolutionary and molecular biology


This has to be a good read! Not just because it might be amusing but also because there is some serious evolutionary and molecular biology here. Our craving for alcohol seems to have a long, long evolutionary history, with a neat mutating gene, ADH4 (No! Not anti-diuretic hormone but alcohol dehydrogenase enzyme), which speeds up the digestion of alcohol, beginning in the mouth. Several primates are known to feast on fermented fruits and there is good evidence that this pursuit of alcohol has or had a significant calorific value for those animals.

From BBC, 23 February 2017



The evolutionary investigation done by Mathew Carrigan and his associates is so very interesting but of course way beyond what the IB might require. Nevertheless, if you are interested enough (Extended essay???) here is a link to the full text of Carrigan’s publication:  http://www.pnas.org/content/112/2/458.full. Early primate ancestors, about 50 million years ago, evidently possessed a gene to produce ADH in some form, and were able therefore to digest alcohol. Some 10 million years ago, primates began foraging on the ground and encountered fallen, fermenting fruit – an excellent source of sugar and thus calories. At about the same time the ADH4 gene underwent a significant, single mutation which enabled some primates to digest alcohol very much more efficiently and therefore be at a competitive and evolutionary advantage. In humans, this gene is one of a bunch of alcohol digesting genes on chromosome 4. The focus upon alcohol in different forms as a source of energy food, pre-dates the supposed time, maybe just 9,000 years ago, when humans apparently first began to enjoy alcohol as a drink and for its pleasurable effects of inebriation. Carrigan even argues that the pleasure ‘kick’ we modern humans get from alcohol can be explained by our ancient ancestors especially seeking out fermented fruits for their high energy value, and thus obtaining a cerebral ‘hit’ of satisfaction, even though they possibly did not obtain significant effects from inebriation.

I love this! it can go on and on and on ….!

What is the mutation? ADH is a zinc based enzyme. (See a molecular visualisation of it here:  http://www.proteopedia.org/wiki/index.php/3cos.) The mutation is one of the most frequent sorts of mutation – a ‘snip’ or SNP, SINGLE NUCLEOTIDE POLYMORPHISM, which occurs when just one nucleotide and its base is changed, resulting in a the synthesis of a modified protein. Research has shown that in humans there are two variants of the ADH1 SNP, with a resultant protein carrying either the amino acid histidine or arginine – effectively two different alleles. The first of these alleles, with the amino acid histidine, is much more effective at the breakdown of ethanol. People with this allele are consequently more tolerant to alcohol. A wonderful piece of research in China has shown how the less effective allele, containing arginine, was selected out of a population about 10,000 years ago. This time coincides with the early domestication of rice in Eastern Asia. Supposedly early humans commonly consumed alcohol derived from the fermented rice. Those with the arginine-coding allele were less tolerant to alcohol and were therefore less likely to have reproductive success, so the allele became uncommon.  (http://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-10-15)


Cytochrome c and cladistics – and much more!


I love the way the new syllabus can bring together different themes, concepts and understandings, through a focus upon one, seemingly small component. An understanding of cytochrome c might bring together and help a comprehension of this lot:

  • protein structure structure (2.4 Proteins & HL 7.3 Translation)
  • function in cell respiration as an electron carrier (8.2 Cell respiration HL)
  • coding gene, CYCS, on chromosome 7 (3.1 Genes & 3.2 Chromosomes)
  • mutations of DNA (1.6 Cell division, 3.1 Genes, 3.4 Inheritance)
  • synthesis of a protein through transcription and translation (2.7 DNA replication, transcription and translation & HL 7.2 Transcription and gene expression & 7.3 Translation)
  • comparing gene sequences in different species to provide support for cladistics and evolutionary arguments (5.1 Evidence for evolution & 5.3 Classification and biodiversity)

What is the specific context? Topic 3.1 – Genes. The IB syllabus suggests that students make a comparison between the amino acid sequences of cytochrome c in different species, using Genbank or some other database. Why cytochrome c? Because this electron carrier in mitochondrial membranes has been studied in depth as molecular evidence for the 3 Domain proposal for the classification of living organisms. Read on …. it is fascinating!

Now comparing amino acid sequences in different species. This is from Biology Second Edition, C.J. Clegg, 2014, Hodder Education and seems to work fine for cytochrome c oxidase, if you follow the instructions and use your head!p-137-gene-bankp-138