Category Archives: 04 Genetics
This week was the first episode of Dara O’Briain’s Science Club from the BBC. The theme: Genetics. Here’s their introductory animated clip, which gives a neat condensed history of sex, genes and DNA:
I’m looking forward to seeing the series!
Wow. Two papers published in Nature Methods have outlined a new technique which allows researchers to track development of embryos (in this case Drosophila melanogaster), in real time. By taking simulataneous multi-view microscopic images of the developing embryo, individual cells can be tracked in real time. The methods are described in more detail at Nature News here.
Have a look at the amazing results below, as a fruitfly embryo develops into a larva, ready to hatch. The two views are the dorsal (upper side) and ventral (lower side) view of the same embryo. See if you can pick a cell and watch its path of development.
Think about how this links to IB Biology topics of cell division, cell specialisation and embryonic development. How does a stem cell know what type of cell to become? If you look closely, there’s a scale bar in the bottom-right. Take a snapshot and calculate the actual length of the embryo.
For more reasons to love fruit flies, check out my mini-review of Fly: An Experimental Life by Martin Brookes.
Image source: Drosophila melanogaster, from Wikipedia.
In 2011, Drew Berry’s animation of the role of breast stem cells won the Imagine Science Film Festival award for visual science (posted here). In this TED Talk, he explains how and why he and his team have put together these accurate representations of invisible cellular processes. The talk shows some examples of the animations, including a really great segment on mitosis and what is happening when spindle microtubules attach and contract.
For more excellent animations, visit the Walter and Elizabeth Hall Institute (WEHI) TV Channel: http://www.wehi.edu.au/education/wehitv/, or their YouTube channel.
The effective communication of Science is an Art.
Neil deGrasse Tyson presents this short PBS NOVA overview of how epigenetics determines the differences between gene expressions in identical twins, how epigenetic variations build up over time and how it affects us. A relatively new, but very interesting field of medicine and genetics, this is a good introduction.
Epigenetics is not directly mentioned in our syllabus, but does help us to connect the ideas of nature vs nurture, genetic variation and inheritance. To what extent does the nurture of our cellular environment (lifestyle) affect the genetic nature of who we are?
For some more really good resources on epigenetics, visit the brilliant Learn.Genetics site from Utah.
Thanks to Ed Yong for posting this on his weekly links roundup.
An entertaining and informative TED talk by medical ethicist Harvey Fineberg on the future of human evolution and the ethics surrounding the decisions that we may soon be able to make regarding our children and our health. With strong links to the Human Genome Project, evolution, ethics, genetic engineering, stem cells and TOK, this is a great video to watch and stimulate discussion and thought in the Genetics unit.
What do you think?
DrosophiLab is a brilliant, free and downloadable piece of software that allows students and teachers to edit fruit flies and carry out crosses. The teacher can use the chromosome editor to set up parent flies of any genotype and there are 20 genes and traits represented, on four chromosomes. This allows for simple monohybrid crosses, sex-linkage, gene linkage and many other combinations – so the problems you set can be differentiated by level. There is also a password-protected teacher setting, to restrict students’ access to results tables and chromosome maps (so they have to work it out for themselves!).
Here are our class resources:
Fly files in this folder: http://www.box.net/shared/dy326rb01d
Chi-Calc (Chi-squared calculator, .xlsx)
How to catch and observe Drosophila:
And this is how you tell the sexes apart:
When trying to observe the flies for real, think about the following questions:
- How are you ensuring ethical treatment of the animals?
- How long would it take to determine the phenotypes of the number of flies you have set for your investigations?
- What difficulties do you encounter when observing the flies?
- What are the limitations or sources of error that might affect the reliability of your results?
Why are fruit flies so important in science?
Science loves fruit flies, and there was even a fruit fly Nobel awarded in 1995 for studies in embryonic development. This links neatly to the assessment statements regarding the differentiation of cells through expression of different genes.
Fruit fly cells are relatively easily observed, and Drosophila makes for an ideal model organism for Mendelian genetics as it has a short life cycle, reproduces quickly and is easily phenotyped.
Drosophila buscki from Journal of Endocrinology
Fruit fly graphic and DrosophiLab banner from DrosophiLab