Year 12 Genetics and Evolution

Reminder: There are three key areas to this topic:

• The source of variation, including meiosis and mutations
• Dihybrid crosses and the inheritance of two traits at once
• Population genetics

 One of the best animations of meiosis I’ve seen!
Here is an extended version (with no narration) placing meiosis in the context of sexual reproduction. (It has a fantastic sequence on fertilisation and mitosis, although takes some artistic licence...)

Another great meiosis clip which covers how it results in variation too.

MEIOSIS AND MUTATIONS

• Stages of meiosis - Beautifully coloured animation with a quiz.
• Meiosis - Nice animation with stage names and controllable slider. Step-through or narrated.
• Mitosis and Meiosis Comparison 1 and Comparison 2 - Animation is the same for both, but quiz differs.
• BBC Biology: Meiosis - Revision bite on meiosis, including a step-through animation and a video which clearly shows crossing over. Test at the end.
• Special features of meiosis - Shows crossing over in closer detail as well as highlights the reduction division
• Crossing over interactive - Click through the stages to see how crossing over creates new combination of alleles (using colours, rather than letters, to represent alleles)
• Crossing Over Causes Genetic Variation - Simple animation showing how crossing over reshuffles alleles and results in unique gametes.
• Meiosis tutorial - Tutorial, diagrams, text, animations, quiz. Pretty long, I guess.
• Independent assortment - The importance of independent assortment in bringing about variation. Animation and text.
• Random orientation of chromosomes during meiosis - Another animation of independent assortment. A pretty one.
• Independent assortment and gamete diversity - An animated and narrated or step-through tutorial and a quiz. Good coverage.
• Independent Assortment Causes Genetic Variation - Simple animations to show how different assortments in each meiotic division of identical cells by meiosis can result in different sets of chromosomes in gametes.
• Evolution 101: Genetic variation - Click through the pages to review how variation comes about, including through mutations and meiosis.
• Genetics and adaptations - Mutations - Includes gene mutations,chromosome mutations, non-disjunction mutations, mutagens and polyploidy. Step-through interactives to help show you the different types.Too much depth for 2011’s Year 12, but still worth bearing in mind.

GENETICS CROSSES

• BBC Science: What is inheritance? - The revision bite that reminds you about inheritance and genetics, from inherited characteristics, through monohybrid crosses and the difference between expected and actual results to sex determination. Of course, there is a test bite at the end.
• BBC Biology: The dihybrid cross - The all-important dihybrid cross. One page overview, then a challenging test.
• Virtual Mouse – genetics - Time limited gizmo (5 minutes?) so work fast! Leads you through the thinking behind inheritance and alleles using a coin-toss model, how genotypes affect phenotypes, and you actually get to breed virtual mice! Also does dihybrid crosses using an online simulator.
• Drag-and-drop genetics cross practice problems - Practise a genetic cross on this interactive webpage. Just stick with this on page, then try the practice problems 1, 2 and 4 on this site.
• Genetics Practice Problems - An excellent way to check if you really know how to do those crosses. Do Monohybrid, Test cross and Dihybrid cross only. The rest can wait till next year.
• Mendelian genetics at The Biology Project - Monohybrid crosses, dihybrid crosses, and sex-linked inheritance. Do these when you are well and truly confident. You need to do your working on a separate sheet of paper.
• Dihybrid inheritance - How independent assortment results in 4 different phenotypes when looking at the inheritances of two traits at once. Uses round/wrinkled yellow/green peas. Interactive.
• Pedigree Problems - Notes on how to spot dominant or recessive conditions, (and whether something is X-linked or not). Not great, but there’s not a lot out there!

EVOLUTION & NATURAL SELECTION

• Genetic drift - Animated tutorial and quiz about drift in plants.
• Natural selection - Animated tutorial and quiz about selection of Darwin’s finches.
• Gene flow - Shows how migration can introduce new alleles to a population.
• Natural selection - Step-through or narrated animation of natural selection of butterflies includng (Batesian mimicry and) stabilising, directional and disruptive selection.
• BBC Science: Survival of the fittest - Evidence for and mechanisms of evolution.
• BBC Biology: Natural selection & speciation - Superb resource for this often difficult topic, including some thoughtful and highly relevant questions and answers. Supported by built-in video clips. (Speciation not needed at Y12 in 2011)
• Nowhere to Hide - Simple interactive where bugs come in two colours: green and orange, and get eaten by birds. You can change the colour of the background and see how that affects the proportion of the population that is each colour of bug
• Evolution in action - Interactive: Change the colour of the background and see what happens to a population of….things. Can keep going with this for ages. Experiment with rapid changes and slow changes to the background colour.
• Peppered moth simulation - Peppered moth simulation with a bluejay. Simulates lichen forest and sooty forest with stationary and moving moths. Can you, as the bluejay, find enough moth to not starve?
• Evolution 101: Natural selection - Click through the pages to review natural selection including how it leads to adaptation and clarifying misconceptions.
• Evolution 101: Genetic drift – Good notes and a model of sampling showing how drift can quickly result in the loss of variation from a population. Some mention of bottleneck and founder effect also.
• Mechanisms of Evolution - A maybe not so good animation depicting the effects of genetic drift, gene flow, mutations, non-random mating, and natural selection on allele frequences in a fish population.
• Founder effect or bottleneck? - Weird animation. The text and narration describe a bottleneck, but the animation is definitely showing founder effect.
• Simulation of genetic drift - What it says. Shows how alleles can be lost or fixed in small populations, but tend not to fluctuate so wildly in large ones. Comes with a short quiz to check understanding.

Science isn't personal: Evolution

I just watched this 10 min video from Qualia Soup about what evolution is, phrased particularly as an argument against people who don't accept it. It has good narration and clear animations to explain important mechanisms of evolution and misconceptions people have about them.

It reminded me that Qualia Soup also has some other good things to say that relate to perception and science:

• open-mindedness
• skewed views of science - how personal bias can get in the way of understanding

Bird brains - song, speech, and genes

Bird brains (Nova Science)
We can learn to talk - how? Studying bird brains can help us find out. This video covers the following.

• How complex is bird song?
  Recordings slowed down sound more musical than you think, and have inspired at least one famous composer.
• What parts of the brain do birds use when singing and listening to song?
  The same parts as we use to speak and listen to speech, as revealed by functional MRI.
• Do birds stutter?
  Yes, some do! And the difference in brain function (from normal singing birds) is similar to the differences human stutterers show.
• Finding a mutant FOXP2 gene (the language gene) involved in an inherited speech disorder by studying an affected family, and then finding FOXP2 in birds and how it relates to song learning.
• The search for other genes that might explan why we can speak, and birds can sing, but other species (e.g. chimps) can't.

The science of decay

AFTERLIFE: THE STRANGE SCIENCE OF DECAY
"Decay: it happens to everything and everyone..."

In this documentary, a biologist sets up a glass box within Edinburgh Zoo and puts lots of stuff in it to see it decay: cooked rice, chilli, cups of tea, a fish, cheese, a fruit bowl, a vegetable box, a raw chicken, sausages, hamburgers, a whole pig on a spit, a compost heap, a wood pile...even a dead rat!

The process of decomposition is observed over a period of 8 weeks using time-lapse cameras and specialist photography to capture the extraordinary way in which moulds, microbes and insects are able to break down everyday things and allow new life to emerge from old.

Highlights:

• Bacteria decomposing a chicken, including how they sense and communicate with each other, and coordinate. (2 minutes)
• How the US Army stops its food going off - extreme preservation! (6 minutes)
• Why we have coal  - plants evolved wood strengthened with lignin well before fungi evolved the ability to digest it and break it down. This meant dead trees ened up lying all over the place, not decaying, and instead vulnerable to burning (especially with all the extra atmospheric oxygen from photosynthesis outpacing respiration). Masses of undecomposed / burnt wood helped to form great deposits of coal. The high oxygen levels also assisted the evolution of large insects, which otherwise have too inefficient gas exchange systems to be able to survive today, and dinosaurs! The end of the age of dinosaurs coincided with a firestorm that probably burned about 25% of the world's forests, leaving less food, less oxygen in the air, and a cooler earth thanks to ash clouds.

Too many highlights! Just watch the whole thing!

The Unbroken Thread

Here is a song produced by Symphony of Science. They take footage of and quotes from prominent scientists and set them to music  using autotune. This video about cells and evolution is called The Unbroken Thread, and features Carl Sagan, David Attenborough and Jane Goodall.