38- Haemophilia

Haemophilia is a genetic condition which is characterised by one of the blood clotting factors, usually encoded for on the X chromosome, not being encoded for properly for various reasons- whether it’s a mobile genetic element inserting itself into the gene or a simple mutation. On the show today, we describe the cause and symptoms of haemophilia, as well as using the case study of Queen Victoria to show that new mutations are a surprisingly common root cause…
Sources for this episode: 1-2) Wikipedia entries for Factor VIII and Queen Victoria (online) [Accessed 08/04/2021]. 3) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition). London: Penguin Books Ltd. 4) Author unknown, The Haemophilia Society (date unknown), Bleeding Disorders > Haemophilia (online) [Accessed 08/04/2021]. 5) Francioli, L. C., et al. (2015), Genome-wide patterns and properties of de novo mutations in humans. Nature Genetics 47(7): 822- 826. 6) Mannucci, P. M. and Tuddenham, E. G. D. (2001), The Haemophilias- From Royal Genes to Gene Therapy. The New England Journal of Medicine 344(23): 1773- 1779.

37- Metapopulations

We’re all familiar with populations, but what about a metapopulation? Put simply, these are populations of populations. Thanks to our sources and also my interpretation of the subject from back when I studied the concept, that’s the notion we’re going to unravel today…

Sources for this episode: 1) Cain, M. L., Bowman, W. D. and Hacker, S. D. (2011), Ecology (Second Edition). Sunderland, Massachusetts, Sinauer Associated Ltd. 2) Thompson, J. N., Encyclopaedia Britannica (2016), Metapopulation (online) [Accessed 17/04/2021]. 3) Wu, J., Encyclopaedia Britannica (2019), Patch dynamics (online) [Accessed 18/04/2021]. 4) In this episode, I use an analogy from how I understood the concept from back when I was taught the concept at university, which I’ve signposted.

36- Hardy-Weinberg Equilibrium

Back in the early 20th century, an English mathematician and a German scientist both independently came up with an equation to portray the frequency of different phenotypes in a hypothetical population. As we’ll see today, this equation rests on some pretty big assumptions which effectively exclude evolution. Why is this useful? Well, because we can use it to see if evolution might be occurring…

Sources for this episode: 1-2) Wikipedia articles for ‘Wilhelm Weinberg’ and ‘G. H. Hardy’. 3)TED-Ed, YouTube (2012), Five fingers of evolution- Paul Anderson (online) [Accessed 18/04/2021]. 4) Thain, M., and Hickman, M. (2014), The Penguin Dictionary of Biology, 11th edition. London: Penguin Publishing Group (p.329- 330). 5) Herron, J. C. and Freeman, S. (2015), Evolutionary Analysis (Fifth Edition, Global Edition). Harlow: Pearson Education Limited (p.257). 5) Chen, B., Cole, J. W. and Grond-Ginsbach, C. (2017), Departure from Hardy Weinberg Equilibrium and Genotyping Error. Frontiers in Genetics 8(167).

35- Five Kingdoms, Three Domains

Today, we’re going to discuss classification. We’re going to briefly skim over how people historically used to organise life, before the establishment of the prokaryote-eukaryote division which would stay in place until an American scientist called Carl Woese rocked the taxonomic boat…
 
Sources for this episode: 1) Craine, A. G., Encyclopaedia Britannica (2020), Carl Woese (online) [Accessed 10/04/2021]. 2) Author unknown, Wikipedia (date unknown), Taxonomy (online) [Accessed 10/04/2021]. 3) Some of the discussion is based on my previous education on the topic, as I completed a Massive Open Online Course ‘Emergence of Life’ covering this topic in 2018.

34- The Tuatara

On the show today, we discuss the tuatara- two species of reptile which are the final representatives of an ancient lineage.

Sources for this episode: 1) Cooke, F., Dingle, H., Hutchinson, S., McKay, G., Schodde, R., Tait, N. and Vogt, R. (2008), The Encyclopedia of Animals: A Complete Visual Guide (p.370). Sydney: Weldon Owen Pty Ltd. 2) Thain, M. and Hickman, M. (2014), Dictionary of Biology (Eleventh Edition) (p.622). London: Penguin Books Ltd. 3) Author unknown, Wikipedia (date unknown), Rhynchocephalia (online) [Accessed 28/03/2021]. 4) Blythe, C. A., Encyclopaedia Britannica (2021), New Zealand (online) [Accessed 28/03/2021]. 5) Campbell, N. A., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Reece, J. B. (2018), Biology: a global approach, 11th edition (Global Edition), Harlow, Pearson Education Limited: p.788- 789.

33- Lethal Alleles

At A Level, we are taught that dominant: recessive traits are in a 3:1 ratio for any trait in which only one gene encodes for it. However, it’s not always that simple. Enter lethal alleles…

Sources for this episode: 1) Author unknown, Wikipedia (date unknown), Lethal allele (online) [Accessed 26/03/2021]. 2) Author unknown, Wikipedia (date unknown), Manx cat (online) [Accessed 27/03/2021]. 3) Gao, Z., Waggoner, D., Stephens, M., Ober, C. and Przeworski, M. (2015), An Estimate of the Average Number of Recessive Lethal Mutations Carried by Humans. Genetics 199: 1243- 1254. 4) Roos, R. A. C. (2010), Huntingdon’s disease: a clinical review. Orphanet Journal of Rare Diseases 2010 5:40. 5) For an example of the deleterious effects of inbreeding as discussed in today’s episode, see the Wikipedia or Encyclopaedia Britannica pages on Charles II of Spain. I might come back to him and his ailments in a separate episode, but until then he will also serve as a good example.

32- Trisomies and Non-Disjunction

Usually, we get two copies of each chromosome. However, the finely tuned process of meiosis and fertilisation can go awry such that a new zygote ends up with three copies. Depending on the chromosome, this can have serious consequences…

Sources for this episode: 1) For an explanation of non-disjunction which I found helpful when I was at sixth form, see: Amoeba Sisters, YouTube (2017), Meiosis (Updated) (online) [Accessed 25/03/2021]. 2) NHS website, Edwards’ syndrome (trisomy 18) (online) [Accessed 25/03/2021]. 3) Xu, X., Zhang, X., Han, J.-W., Adamu, Y. and Zhang, B. (2020), Potential Increased Risk of Trisomy 18 Observed After a Fertilizer Warehouse Fire in Brazos County and TX. International Journal of Environmental Research and Public Health 17: 2561- 2571.

31- Choanoflagellates

We often think about animals as an insular group. However, as with any genetic grouping, animals do have close relatives. On the show today, we discuss choanoflagellates- considered the closest relatives to animals today, and possibly a good candidate for what the common ancestor of all animals would have looked like.

Sources for this episode: 1) Campbell, N. A., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Reece, J. B. (2018), Biology: a global approach, 11th edition (Global Edition), Harlow, Pearson Education Limited. 2) The Editors, Encyclopaedia Britannica (2021), Choanoflagellate (online) [Accessed 13/03/2021]. 3) Marshall, M., New Scientist (2009), Timeline: The evolution of life (online) [Accessed 13/03/2021]. 4) Holland, S. M., Encyclopaedia Britannica (2021), Ordovician Period (online) [Accessed 13/03/2021]. 5) Philippe, H., et al. (2009), Phylogenomics Revives Traditional Views on Deep Animal Relationships. Current Biology 19: 706- 712.

30- Measures of Diversity

Biodiversity is often mentioned as one concept in popular culture. However, it can be split into different components depending on who you ask. Today, we’re going to explore two different ways of chopping biodiversity up.

Sources for this episode: 1) Author unknown, Wikipedia (date unknown), Gamma diversity (online) [Accessed 06/03/2021]. 2) Cain, M. L., Bowman, W. D. and Hacker, S. D. (2011), Ecology (2nd edition). Sunderland: Sinauer Associates Ltd. 3) For a formula for Shannon’s index of biodiversity (which I’m going to try and discuss in a future episode), see: Fullick A., Locke, J. and Bircher, P. (2015), A Level Biology for OCR A. Oxford: Oxford University Press.

29- Sympatric Speciation

This week, we’re going to discuss sympatric speciation- the counterpart to allopatric speciation where no physical barrier is needed.

Sources for this episode: 1) Thain, M., and Hickman, M. (2014), The Penguin Dictionary of Biology, 11th edition. London: Penguin Publishing Group. 2) Campbell, N. A., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Reece, J. B. (2018), Biology: a global approach, 11th edition (Global Edition), Harlow, Pearson Education Limited. 3) Author unknown, Understanding Evolution (berkeley.edu), Sympatric speciation (online) [Accessed 28/02/2021]. 4) Author unknown, National Geographic (date unknown), Speciation (online) [Accessed 28/02/2021].