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The Structure of DNA

The Structure of DNA

Welcome to the DNA Unit!

This unit called "The structure of DNA" is divided into three stages. In stage 1, you are going to practice your listening skills watching/listening to the video called "DNA structure and replication". Several activities will be proposed in order to work its content. In stage 2, you can deepen in the DNA structure making a 3D DNA model and researching about its main components. And in stage 3, you are going to practice your reading skills and writing skills working with a science article called “Can you tell your Ethnic identify from your DNA?” where you will be able to know the importance of DNA in the different ethnics. Finally, you can check the new contents learnt through the consolidation suggested activities.

In this unit, the teacher will evaluate all the proposed tasks. In addition, he/she will take into account the language knowledge and student´s behaviour. You can consult the evaluation criteria in the lesson plan of the unit.

After this presentation of the unit is time to work so pay attention to the instructions to follow the correct development of the activities.

Stage 1

Brainstorming activity

The first step is to gather some information about your previous knowledge so, it is time to think!. For this purpose, click on the button "First activities " and think about the suggested questions in Brainstorming activity. After a few minutes thinking, share your answers with the whole class by the guidance of the teacher.

Glossary activity

Now you have to focus on the Glossary, that you can find clicking the same button, where you are going to find a list with the specific vocabulary in English that you need to know to follow and understand the teacher´s explanations and the proposed activities. With the guidance of the teacher, a student has to read a word out loud and explain its meaning. Then the rest of the group have to repeat the word loud, all together, focusing on the pronunciation. In addition, each student has to write each word in his/her notebook focusing on the grammar.

Video from Khan academy resources (listening activity)

The following step is to watch and listen to the video called "DNA structure and replication" which is presented at the beginning of the unit. You will only watch/listen the first 5 minutes and 36 seconds to the video because the process called Replication will be learnt later. First of all, you have to watch/listen to the video without transcription and without taking notes, only listening to understand its content and focusing on the specific words that you have previously seen with the teacher. Once the first listening is done, the teacher will take the next few minutes to resolve doubts. Then you can watch and listen to the video a second time. This time you can support your listening with the transcription presented below in order to facilitate its meaning with the support of Wordlink tool. While you are watching and listening to the video you have to complete the text that you can find clicking the button "Video activity" with the information of the video. This activity has been designed to work in pairs (the teacher will make the pairs taken into account different aspects) and its purpose is to help you to get focused while you are watching/listening to the video.

Once the activity is completed, the teacher will guide a brief discussion with the whole class. Firstly to correct the activity and secondly to focus on determining the general structure of DNA and its importance to life.

In order to help you with the speaking, you can click on the button "Language support" where you can find useful expressions that will support your speaking.

Transcription of video

Hank: It's just beautiful, isn't it?

0:04
It's mesmerizing. It's double-helixciting.
0:09
Really can tell just by looking at it how, sort of, important and amazing it is.
0:13
It's pretty much the most complicated molecule that exists,
0:17
and potentially, the most important one.
0:20
It's so complex, that we didn't eve know for sure what it looked like
0:23
until about 60 years ago; and so multifariously awesome,
0:27
that if you took off it from just one of our cells and untangled it,
0:30
it would be taller than me.
0:32
Nowt considering that there are probably 50 trillion cells in my body,
0:36
right now, laid end to end, the DNA in those cells
0:39
would stretch to the sun, not once, but 600 times.
0:44
Mind blown yet? Hey, you wanna make one?
0:48
(upbeat music with whistling)
0:58
Of course you know, I'm talking about deoxyribonucleic acid,
1:00
known to its friends as DNA.
1:03
DNA is what stores our genetic instructions,
1:05
the information that programs all of our cells' activities.
1:08
It's a 6 billion letter code that provides
1:10
the assembly instructions for everything that you are.
1:13
And it does the same thing for pretty much every other living thing.
1:17
I'm gonna go out on a limb here, and assume that you are human,
1:19
in which case, everybody cell that you have, or somatic cell in you,
1:23
has 46 chromosomes, each containing 1 big DNA molecule.
1:28
These chromosomes are packed together tightly
1:30
with proteins in the nucleus of the cell.
1:32
DNA is nucleic acid, and so is its cousin,
1:35
which we'll also be talking about, ribonucleic acid, or RNA.
1:38
Now, if you can make your mind do this,
1:40
remember all the way back to episode 3, where we talked about
1:42
all of the important biological molecules,
1:45
carbohydrates, lipids and proteins. That ring a bell?
1:47
Well, nucleic acids are the 4th major group of biological molecules,
1:51
and for my money, they have the most complicated job of all.
1:55
Structurally, they're polymers, which means that each one
1:57
is made up of many small repeating molecular units.
2:00
In DNA, these small units are called nucleotides;
2:02
link them together and you have yourself polynucleotide.
2:05
Now, before we actually put these tiny parts together
2:07
to build a DNA molecule like some microscopic piece of IKEA furniture,
2:11
let's first take a look at what makes up each nucleotide.
2:14
We're gonna need 3 things:
2:15
1. A 5-carbon sugar molecule,
2:17
2. A phosphate group,
2:18
and 3. 1 of 4 nitrogen bases.
2:21
DNA gets the first part of its name from our first ingredient,
2:23
the sugar molecule, which is called deoxyribose;
2:26
but all the really significant stuff, the genetic coding that makes you,
2:30
is found among the 4 nitrogenous bases,
2:32
adenine, thymine, cytosine, and guanine.
2:35
It's important to note that in living organisms,
2:37
DNA doesn't exist as a single polynucleotide molecule,
2:39
but rather a pair of molecules that are held tightly together.
2:43
They're like an intertwined, microscopic, double-spiral staircase;
2:47
basically, just a ladder, but twisted.
2:49
The famous double-helix.
2:51
And like any good structure, we have to have main support.
2:53
In DNA, the sugars and phosphates bond together to form twin backbones.
2:58
These sugar-phosphate bonds run down each side of the helix,
3:00
but chemically, in opposite directions.
3:03
In other words, if you look at each of the sugar phosphate backbones,
3:05
you'll see that 1 appears to be upside down in relation to the other.
3:08
One strand begins at the top with the first phosphate
3:10
connected to the sugar molecule's 5th carbon,
3:12
and then ending where the next phosphate would go,
3:15
with a free end at the sugar's 3rd carbon.
3:17
This creates a pattern called 5-prime and 3-prime.
3:20
I've always thought of the deoxyribose with an arrow,
3:23
with the oxygen as a point; it always points from 3 prime to 5 prime.
3:27
Now, the other strand is exactly the opposite;
3:29
it begins up top with a free end at the sugar's 3rd carbon,
3:32
and the phosphates connect to the sugar's 5th carbons all the way down,
3:35
and ends at the bottom with a phosphate,
3:38
and you've probably figured this out already,
3:39
but this is called the 3-prime to 5 prime directions.
3:42
Now, it is time to make ourselves one of these famous double-helices.
3:46
These 2 long chains are linked together by the nitrogenous bases
3:50
via relatively weak hydrogen bonds.
3:52
But they can't just be any pair of nitrogenous bases.
3:55
Thankfully, when it comes to figuring out what part goes where,
3:57
all you have to do is remember that if 1 nucleotide has an adenine base,
4:01
only thymine can be its counterpart;
4:03
likewise, guanine can only bond with cytosine.
4:05
These bonded nitrogenous bases are called base pairs.
4:09
GC pairing has 3 hydrogen bonds, making it slightly stronger
4:12
than the AT base pair, which only has 2.
4:15
It's the order of these 4 nucleobases, or the base sequence,
4:18
that allows your DNA to create you.
4:21
So, AGGTCCATG means something completely different as a base sequence
4:26
than say, TTCAGTCG.
4:29
Human chromosome 1, the largest of all of our chromosomes,
4:31
contains a single molecule of DNA with 247 million base pairs.
4:36
If you printed all of the letters of chromosome 1 into a book,
4:40
it would be about 200,000 pages long, and each of your somatic cells
4:44
has 46 DNA molecules tightly packed into its nucleus;
4:48
that's 1 for each of your chromosomes.
4:51
Put all 46 molecules together, and we're talking about roughly
4:54
6 billion base pairs in every cell.
4:58
This is the longest book that I have ever read.
5:01
It's about 1,000 pages long. If we were to fill it with our DNA sequence,
5:04
we'd need about 10,000 of them to fit our entire genome.
5:09
Pop quiz! Let's test your skills using a very short strand of DNA.
5:14
I'll give you 1 base sequence, you give me the base sequence
5:17
that appears on the other strand.
5:18
Okay, here goes. So, we've got a 5-prime AGGTCCG to 3-prime.
5:23
And ...
5:25
Times up, the answer is 3-prime TCCAGGC 5-prime.
5:29
See how that works? It's not super complicated,
5:31
since each nitrogenous base only has 1 counterpart,
5:34
you can use 1 base sequence to predict
5:36
what its matching sequence is going to look like.

Concept map

Organizing your thoughts and visualizing the relationship between key concepts in a systematic way it is really important for the learning process. For this reason, now it is the time that you design with your pair a concept map which shows the relationship between DNA, genes and chromosomes. You have to click on the button "Video activity" where you will find several sticky notes that you will have to order in order to create a concept map with sense.

Interactive activity from Learn.Genetics resources

You are going to finish this session in a funny way because it is time to play. With your partner, you are going to review the structure of DNA with an interactive activity called “Build a DNA molecule” focusing on Chargaff´s rules about the complementary pair of bases.

You can start to play clicking the button "Interactive activity"

Even though it is a game, you should pay attention to the activity because it will help you to consolidate the new contents explained.

The teacher will go around the class evaluating this activity.

Finally, at the end of this session, you have to hand over your glossary to the teacher and send by Classroom tool the video activity (gap-filling test) and the concept map in order to be assessed by the teacher.

Stage 2

3D DNA model

You are going to start this session making handicrafts because your new goal will be to elaborate in detail a 3D DNA model. Keep calm! this task requires time so you are going to work it in groups of 3 or 4 (6 groups approximately). The teacher will make the groups taken into account different aspects and he/she will give you the materials needed.

Now click the button "DNA model" and follow the instructions of method 2 in order to elaborate successfully your DNA model.

Once the model has been completed, your group will have to deepen in the DNA structure looking for information about its components such as Carbon sugar Deoxyribose, phosphate group, nitrogenous bases (cytosine, guanine, thymine and adenine) and basic structure (twisted ladder/double helix). For this research you will have to consult the following links:

http://www.chemguide.co.uk/organicprops/aminoacids/dna1.html

http://www.news-medical.net/life-sciences/Structure-of-DNA.aspx

Finally, each group will share their research work with the rest of the classmates preparing a brief oral presentation with the support of a PowerPoint presentation.

In this case, the students will evaluate the oral presentations and PowerPoint presentations.

In order to support this task, clicking on the button "Language support" you can find useful material such as tips for preparing the oral presentation, useful sentences and vocabulary, tips for creating a PowerPoint presentation and the rubrics for the oral-PowerPoint evaluation and DNA model evaluation.

At the end of the session, your group will hand over the DNA model and you will send by Classroom tool the PowerPoint presentation to the teacher in order to be evaluated.

Stage 3

Reading science article and write a short review

Welcome to the last session where you are going to start reading a very interesting science article called “Can you tell your Ethnic identify from your DNA?”. You can access to the article clicking on the button "Science article". Remember that you can support your reading skills using Wordlink, a useful online reading tool which allows linking all the words in a given web page to the online dictionaries available from Multidict. After the reading task, it is time for practice your writing skills. Now you will have to write a short review about its content. In order to direct your reflexion, I suggest you some questions that you have to answer:

  • What is the main argument of the article?
  • What does evidence (datum, facts, studies…) the article contain to confirm its argument?
  • Are you in agreement with the conclusions proposed in the article? Explain your answer.
  • What do you think about the implications in the society of the subject set out in the article?
  • What implications does it have for you?

This activity is proposed as an individual task in order to practice your reading skills and writing skills.

Additionally, the teacher will acknowledge the cultural diversity of their student always encouraging cultural acceptance. For this reason, another goal of this task is that students are aware of the importance of DNA in the ethnic peculiarities and as a result of that to achieve an atmosphere of respect among people regardless of their ethnical membership. With this purpose and after the writing task, the teacher will manage a class discussion where you can share your opinion with your classmates. Remember that you can support your speaking skills and writing skills with useful expressions that you can find clicking on the button "Language support".

You will have to send by Classroom tool your review to the teacher in order to be evaluated.

Closure activities

Differences and similarities between DNA and RNA (Venn diagram) and DNA Crossword.

In order to finalize the lesson, you will have to work two activities to consolidate the new concepts learnt. Again, you will work it with your pair. Clicking on the button "Consolidation activities" you will find a worksheet with two tasks. The first one is a Venn diagram where you will have to research about differences and similarities between DNA and RNA and, the second one, is a DNA crossword where you will review in a funny way the new concepts learnt. This activity is suggested in order to help you retain and reinforce the new content. Remember that consolidation is a good opportunity to clarify and address any doubts.

By the end of the session, you and your pair will have to send the worksheet to the teacher in order to be evaluated.
 
At that point, you have reached the end of the unit. I hope you have got the proposed goals in a funny and effective way.
 
Clilstore First activityDNA modelInteractive activityScience articleLanguage supportConsolidation activitiesVideo activity

Short url:   https://clilstore.eu/cs/4967