To model the difference between linked and unlinked genes I used an activity I created that you should view here.
How it works:
By keeping some “alleles” linked and some “unlinked” we observe a difference in the inheritance pattern.
My initial instructions for this worksheet weren’t very clear but I think they are much better now. Ideally it will be printed so that the maternal genes are printed in one colour (let’s say pink, even though it’s a socially constructed convention. Let’s talk about that another time) and the paternal genes are a different colour. If I were to teach this again I would create a class set of laminated linked genes and laminated unlinked genes. The students spent far too long cutting them out themselves and I don’t think the actual process of cutting them adds anything to the learning experience.
Why is linkage important? The linkage of genes has huge implications for the inheritance of alleles. Genes which are on the same chromosome do not randomly segregated in meiosis. They physically cannot because they are on the same chromosome and so are inherited together.
Oh if only biology were so simple. NOT. That would be boooooooring! Evolution is way more sophisticated than that.
In fact, we have a process called crossing over that swaps a little bit of DNA between homologous chromosomes so your maternal and paternal DNA can be rearranged into each of your gametes. So if you can imagine, genes which are closer together are more likely to stay together. It would be very unlikely for a crossing over event to happen right at the exact spot where one gene ends and the other starts and so genes which are closer together tend to stay together.
This is quite a controversial and murky topic when it comes to science (which is something scientists are not always comfortable with let me assure you!). This is because, as you will see for yourself, it is really difficult to define health and disease. I tried to come up with a list of different conditions that might be difficult to classify as “healthy” or “not healthy” if we are to use the World Health Organization definition of health. That is a “complete state of physical, mental and social wellbeing and not merely the absence of disease or infirmity”.
Complete the poll to see what you think. Also, I’d love to make this list even longer, comment with suggestions as to other conditions, which may be difficult to classify. This form of assessment for learning allowed my students to engage critically with the syllabus requirements and is an integral part of my teaching practice (Quality teaching in NSW Public Schools, 2003). Scroll to the bottom if you want to download the lesson in Word format.
While teaching Year 12 students I noticed from their questions that many of them had not yet grasped the concept of DNA structure and organisation clearly. This was very surprising for me, mostly because (1) they were at a selective school so I naively thought that that must mean they would miraculously grasp concepts (2) we were in our 3rd term in the HSC, they should know it by now! To me, huge red flags started signalling and I approached my supervising teacher asking if she would allow me to deviate from the plan and take a lesson to revise key issues. Thankfully she agreed, although I know a little reluctantly, there is a lot of pressure to “get through” content. I couldn’t have these kids get to their final exams and not understand what a chromosome really is. After all, they were doing the core topic in biology – blueprint of life and they were also doing the genetics option. Effectively they could’ve been tested on this content twice. It was a huge gamble if I didn’t go through it.
So I prepared a series of questions aimed at pinpointing their issues. I projected these on the board and handed out laminated sheets of white paper – that I call mini-whiteboards – to each of the students and some markers and we had a quizzing and intervention session. I’d ask a question they’d respond and if it was clear that a few of them (I think I revised concepts if even 3 of them were unsure) weren’t clear we’d go through it.
From their questions it was clear that the concepts of DNA organisation was completely lost on them. They still weren’t clear on what an allele was, what a gene is and how chromosomes organise DNA or what their functions were.
It’s an abstract concept so I totally understand this confusion. If you’re teaching students about DNA, the following analogy I used might help.
All the DNA that we have in each somatic cell is a complete set called a genome. Let’s pretend this is the Encyclopaedia Britannica. You know how we have A-Z and each book has one section of the Encyclopaedia, well our DNA is organised into a similar mechanism. Each large of DNA is called a chromosome. Our chromosomes are different, just like an Encyclopaedia. The A entries are totally different form the G entries. But we need a complete set of A-Z for a complete encyclopaedia. Similarly, we need a complete set of chromosomes 1-23 for a complete genome. To add a little complexity to it, we don’t just have one set of DNA we have two. One from our mother and one from our father. So if we continue with the Encyclopaedia example this is like if we have a whole set of Britannica and another set of the World Book Encyclopaedia. We find the same entries in there, like you’ll find a definition for apple in each but they might be slightly different.
So let’s take it a step further. Each entry in the encyclopaedia is like a gene – it has a meaning and in cells that meaning is a protein. Each gene is made up of DNA in a combination of a series four bases (ATCG) these letters are what make up DNA. Similarly, definitions are made up of words.
So let’s recap.
Broken up into books, A-Z
Broken up into chromosomes 1-23
Come in different brands
Come in different alleles. We have one of each of mum’s alleles and one of dad’s.
Each book has different entries
Each chromosome has different genes
Entries are made up of words
Genes are made up of nucleotides
Words are made up of letters
Nucleotides are made of sugar, phosphate and bases. Each base is made of either an A, T, C or G.
What do you think? My kids loved this analogy and their relief was the most satisfying aspect of my first practicum. I want to know if you think it will work for you!
If I had a gun to my head and absolutely HAD to pick a favourite topic in biology, I would probably choose mitosis and meiosis. I can’t imagine that this would ever be the case, but you know, it paints a pretty picture. After 7 years of studying meiosis I still have to think about how to spell it – I don’t know what it is, I just find it so tricky. Anyway, mitosis. I taught this for my very first time on my first teaching practicum and the students absolutely ate it up.
Let me explain why.
So you know how when you’re really excited about something you become very animated about it and you can’t help but infect everyone with your excitement. Yeah that’s pretty much what happened. You can see the powerpoint I used to help in my presentation and you can pretty much feel the excitement leaping out at you.
I stole borrowed a lot of ideas from the one and only Hank Green of the VlogBrothers. They have an amazing YouTube series called Crash Course. Here, go watch it and come back.
Oh hai there. Welcome back!
So what I basically did was tell my students (half of whom were on an excursion anyway) put your books away. This is the most exciting story you will ever be told and I don’t want you to write anything I just want you to listen. In retrospect I probably should’ve “Checked for Understanding” but I was a novice. I might do it slightly different in future. I told them about how at a cellular level our bodies are incredible. We make over 300 billion cells per day. Just try to wrap your head around that for a second. There are 7 billion people on the planet. Gosh I love science.
So even on your laziest day where you watch 2 whole seasons of Orphan Black because your student may have told you that it’s a really good show to watch and you totally agree cause it’s about cloning. Even on those days you are freaking incredible. Then I said to them: When do we even need mitosis? What is it?
You cut your finger and your skin needs to repair itself.
You’re a newborn and you want to grow bigger and taller.
Your immune system wants to fight off disease.
Your stomach lining is eaten away by the cells they produce.
Are you noticing a pattern here? And half the class said BAM MITOSIS. It was a good moment.
So many of you will already be aware that there isn’t one scientific method. The one we usually learn and teach about however, goes a bit like this:
Looks familiar right? Now remember when I said there isn’t only one scientific method, let’s consider the field of epidemiology. In epidemiology which is a branch of biology we try to understand human diseases, how they originate, how they spread, what are some factors that predetermine the acquisition of disease and so on. Now it’s really frowned upon to do experiments on people. For example, we can’t PROVE that smoking causes lung cancer because we can’t say “Oi, you 30 people, come over here and smoke for the next 20 years of your life and we’ll see if you get lung cancer, and you 30 over there, you’re fine just don’t smoke”. I’m sure you can see how ridiculous that would be!
So how do we get around this problem? Well by a lot of observation. Epidemiology relies on life already carrying out the method and results, and epidemiologists just go out and try to observe people and find patterns. It’s a very complicated but extremely fascinating process that relies very much on statistics. I might do a post on the bell curve if I get a chance – it’s actually really cool.
So anyway, here is a template you can use with high school students to scaffold for them the (traditional) scientific method.
Can you think of another situation where the classical scientific method doesn’t hold true?
Patience: teachers need to give each student a fresh chance every single day. Teachers also have to be patient when explaining concepts to their students and try to explain it in different ways.
Organisation: There is nothing worse than a teacher who is unorganised, because it gets transferred to your students. Similarly,
Passionate: Teachers who are passionate transfer this passion to their students. They want to know why you think your subject is so amazing.
Are firm but fair: They are compassionate and try to understand their students but lay down the law when needed.
Have high expectations of their students: They will meet whatever expectations you set them.
Model a love of learning: They seek new ideas and ways of doing things and don’t do the same thing year in year out.
Good communicators: They build networks with other teachers, they ask and seek advice.
Ask the good questions: They help their students become critical, self sufficient thinkers.
Plan activities that meet students needs with FUN at the core of them.
Reflective: On their own teaching practices.
Engage their students: by making it relevant to them.
Have routines for what goes on in the classroom
Timing of lesson is well thought out.
Assess their students constantly and use this to inform (a) future teaching of this class (b) teaching the same topic to future classes. It’s not good enough to just teach the content. You need to know that your students know the content.
Fantastic pitcher: So that the questions or activities that you ask of your students are just beyond what they are capable of doing comfortably now. You want them just outside their comfort zone.
Approachable: You want your students to feel like they can ask you questions and not be ridiculed.
Clearly outlines the aims of the lesson: The worst question your student can have at the end of the lesson is “So…what were we supposed to learn then?”. Make it super clear.
Extremely passionate about education, my main drive is ensuring the spark of natural curiosity that we all have as children isn’t lost throughout schooling but encouraged and ignited. I want to foster a lifelong love of learning in my students and show them how enchanting science truly is. I intend to instill a sense of pride in students’ learning to constantly push them towards their personal best. With my support and guidance they will become critical thinkers, who engage with their learning and one another. We will achieve this through problem solving, meaningful assessments and collaborative small group work. As a great deal of effective student learning comes from organisation and routine, my ideal school will allow me to have my own classroom and focus on engaging students through the curriculum.