|
Sunday Science: Extracting DNA 提煉DNA
Welcome to Sunday Science! Every Sunday, we're going to guide you through some cool experiments that you can do at home. It's a good idea for you to keep a record of what you do in a Science Journal. That way you can record what you learn, compare results and maybe use them to design new experiments! Have a look at the Science Journal box for some ideas to get you started. Remember to always ask a grown-up's permission before trying out an experiment.
歡迎閱讀《週日科學版》！我們每週日都要為你介紹可以在家中進行的有趣科學實驗。你可以在《科學日誌》中記錄自己做了哪些活動，這樣就可以將所學的紀錄下來，比較這些結果，也許還可以利用它們來設計新的實驗！先看一下《科學日誌》的點子再開始吧。展開實驗之前，記得要獲得大人許可喔！
Sunday, Dec 30, 2007,Page 14
|
|
PHOTO: CATHERINE THOMAS, TAIPEI TIMES
照片: CATHERINE THOMAS
|
Have you heard of DNA? Every living organism has DNA. It is a little bit like an instruction manual which tells living things how to grow and even decides how they look. This week we're going to extract DNA from a kiwi fruit. Make sure that a grown-up helps you with this experiment.
What you will need:
Some tall narrow glasses
(champagne flutes work well)
to act as test tubes
Salt
Rubbing alcohol (you can buy this at a chemist)
Water
Dish detergent
A kiwi fruit
A coffee filter
A measuring jug
A kettle
Bamboo skewers
A bowl and a spoon (or a pestle and mortar)
A knife
Two jars
1.Put the rubbing alcohol in the freezer to chill it.
2.Peel the kiwi fruit. Chop it into small pieces.
3.Put the kiwi fruit into the bowl and mash it up until it is pulp.
4.In a jar place 100ml of tap water. Add half a teaspoon of salt and two-thirds a tablespoon of dish detergent. Stir very gently. You want to avoid making any bubbles. When the salt is dissolved you have made an extraction buffer.
5.Carefully add the extraction buffer to the kiwi and mash up the mixture. You want to extract as much DNA as possible, but you have to be careful not to make bubbles. The more you pulp the mixture, the more DNA you will get.
6.Pour the pulp into a jar.
7.Now comes the tricky part. You need to make an incubator. Boil some water. Ask a grown-up to help you put some of the boiling water into the measuring jug. Then ask him or her to add the same amount of tap water. You want the water to sit around the jar with the pulp in it, so how much you use will depend on the size of the jar. The water tempurature should be around 60°C.
8.Leave the pulp incubating for 15 minutes. You can use this time to wash up the spoon and bowl and tidy up your workspace.
9.Place a coffee filter in the neck of a clean, dry jar. Spoon a bit of the pulp into the filter. Slowly add all the pulp. You'll have to be patient as this can be a little slow. At the end you will have a jar of fluid and filter paper full of pulp. Throw the filter and the pulp away.
10.You should have enough fluid to make several samples. Pour some fluid into your "test tube" until it is a third full.
11.Ask a grown-up to help you with the ice-cold alcohol. Put about 100ml into the measuring cup. Very slowly pour the alcohol down the side of your test tube. You want the alcohol to sit on top of the fluid, making a second layer. Use about the same amount of alcohol as kiwi fluid.
12.Set the test tube down. Watch carefully. A white spongy substance should be forming above the kiwi fluid at the bottom of the alcohol layer. This is DNA!
13.After a few minutes you can use the bamboo skewer to spool in the DNA, but be very gentle. When you think you have enough you can pull it out of the tube. It's safe to play with it, but don't eat it!
(CATHERINE THOMAS, STAFF WRITER)
你聽過DNA（脫氧核糖核酸）嗎？所有生物都有DNA，它有點像是一本會指導生物如何成長，甚至決定他們外觀的使用說明書。本週我們要從奇異果中提煉DNA，務必請一位大人從旁協助你做這個實驗。
所需材料︰
數個細長的杯子（香檳杯效果最好）當作試管用
鹽巴
外用酒精（可在藥局買到）
水
洗碗精
一顆奇異果
一張咖啡濾紙
一個量杯
一個水壺
竹籤
一個碗和一支湯匙（或搗研缽和杵）
一把刀
兩個瓶子
1.將外用酒精放到冰庫冷凍。
2.將奇異果去皮，切成小塊。
3.將奇異果放入碗中搗成泥。
4.將一個瓶子裝入一百毫升的自來水，再加入半茶匙的鹽和三分之二湯匙的洗碗精，非常輕地攪拌，避免弄出任何泡泡。待鹽完全溶解後，「提取緩衝液」就完成了。
5.小心地將提取緩衝液加到奇異果中，並搗拌混合物，雖然希望提取愈多DNA愈好，但是要小心別搗出泡泡，你搗得愈細就會得到愈多DNA。
6.將搗好的混合物倒入一個瓶子中。
7.接下來的步驟比較難處理，你得做出一個「培養器」。煮沸一些水，然後請一個大人幫你將沸水裝入量杯中，再請她或他在量杯中倒入等量的自來水，因為裝有果泥的瓶子要置放在量杯的自來水中，所以可以以瓶子的大小來衡量所需的水量，水溫應在攝氏六十度左右。
8.將培養器靜置十五分鐘，你可以利用這段時間清洗碗和湯匙，並整理工作區域。
9.在一個乾淨的乾瓶子瓶口套上咖啡濾紙，用湯匙舀一點果泥至濾紙中，然後慢慢將所有果泥都加到濾紙中，這可能會花上一段時間，你得有點耐心。最後，你會得到一瓶液體，而果泥會留在濾紙上。將濾紙和果泥一起丟掉。
10.你得到的液體應該夠做幾個樣本。將一些液體倒入「試管」中至三分之一滿。
12.請大人幫你使用冰的酒精，先在量杯中倒入約一百毫升，然後非常緩慢地沿著試管邊緣注入酒精，讓酒精浮在液體上，形成兩層；酒精份量需要和奇異果液體差不多。
13.靜置試管，仔細觀察，在奇異果液體層上方的酒精層底部應形成一團白色海綿狀物質，這就是DNA！
14.數分鐘後，你可以將竹籤戳進DNA中纏繞，但是動作要非常輕柔，當你覺得夠多了，就可以將它拉出試管。你可以玩它，但千萬不可食用！
（翻譯︰袁星塵）
| What's the science? 科學原理 |
| DNA is stored in the nucleus of cells. To get to the nucleus, you must break through the outer layers of the cells. When you mash up the kiwi, you start to break down the outer wall of the cells. The dish detergent attracts the lipids and the proteins of the second layer of the cells. DNA has a negative charge, while salt has a positive charge, so the salt neutralizes the DNA, which makes the DNA easier to extract. When you incubate the pulp, it helps the cells to break down even more. Kiwi fruit naturally contains enzymes which further help the proteins to break down so that you can get to the DNA. When you pour the alcohol on top of the kiwi fluid, the alcohol stays on top because it's less dense. Denser parts of the cells will stay in the kiwi fluid, but the DNA floats to the top. It's more dense than alcohol, so it floats in the middle. DNA can't dissolve in alcohol, so you can actually see it.
DNA存在於細胞的細胞核內，為了取得細胞核，你必須突破細胞外層，當你攪碎奇異果時，你就在分解細胞外壁了；洗碗精吸引細胞第二層的脂質和蛋白質；DNA帶有負電荷，而鹽帶有正電荷，因此鹽中和了DNA，使得DNA更容易被提煉出來。培養果泥的過程，有助於細胞更加分解。奇異果本身蘊含酵素，讓蛋白質層更容易被分解，你才能取得DNA。當你將酒精倒入奇異果液體時，因為酒精的密度較小，會停留在上層；細胞中密度較大的部份會留在奇異果液體中，但DNA會漂到上層，DNA的密度大於酒精，因此會停留在中間；DNA不溶於酒精中，因此你可以清楚地看到它。 |
|
|
| Vocabulary 今日單字 |
|
1. DNA n.
脫氧核糖核酸 (tuo1 yang3 he2 tang2 he2 suan1)
2. organism n.
有機體 (you3 ji1 ti3)
3. extract v.t./v.i.
提煉 (ti2 lian4)
4. test tube n.
試管 (shi4 guan3)
5. rubbing alcohol n.
外用酒精 (wai4 yong4 jiu3 jing1)
6. mash v.t.
搗成糊狀 (dao3 cheng2 hu2 zhuang4)
7. pulp n.
糊狀物質 (hu2 zhuang4 wu4 zhi2)
8. extraction buffer n. phr.
提取緩衝液 (ti2 qu2 huan3 chong1 yi4)
9. incubator n.
培養器 (pei2 yang3 qi4)
10. spongy adj.
海綿狀的 (hai3 mian2 zhuang4 de5)
11. spool v.t.
纏繞 (chan2 rao4)
12. lipid n.
脂質 (zhi1 zhi2)
13. protein n.
蛋白質 (dan4 bai2 zhi2)
14. enzyme n.
酵素 (xiao4 su4) |
|
|
This story has been viewed 964 times.
|
Print
Mail