Một phân tử ADN của một tế bào có hiệu số %G với nuclêôtit không bổ sung bằng 20%. Biết số nuclêôtit loại G của phân tử ADN trên bằng 14000 nuclêôtit. Khi ADN trên nhân đôi bốn lần, hãy xác định:

a. Số nuclêôtit mỗi loại môi trường cung cấp cho cả quá trình trên.

b. Số liên kết cộng hoá trị được hình thành trong quá trình.

c. Số liên kết hiđrô bị phá huỷ trong cả quá trình trên.

Một đoạn mạch đơn của phân tử ADN có trình tự sắp xếp như sau:

A-T-G-X-T-A-G-T-X

Xác định trình tụ các nucleotit trong đonạ gen đã tổng hợp ra đoạn mạch ẢN trên

ARN chia làm 3 loại căn cứ vào đâu?

Để xác định giống thuần chủng hay không thuần chủng cần phải thực hiện phép lai nào

1.xác định số lượng từng loại nu của gen:

gen 1 có 120 vòng xoắn,A=3G

Last weekend, I had a day trip to the countryside with some of my classmates. We went to visit a farm on (1)....................Perter's Uncle Tom works.

We left early in the morning and went the by bus. Uncle Tom and some workers met us at the bus stop and (2)...................us to the farm. On the way, Uncle Tom showed us (3) ...................of wheat, corn, and vegetables where some tractors were running up and down ,plowing and breaking soil, distribusting manune and (4).................seeds. After lunch, we all went for a walk round the farm. In the large yard of the farm we saw a lot of (5)......................... machinery. In the afternoon we went to the catter farm. A lot of horses, sheep and cows were (6)....................here. We saw a new-born (7)................... in the cowshed when we helped the farmers to feed the cows. After having some tea and cakes we said goodbye and went home. It was an (8) .................day!

I. Complete the sentences with the correct form of the words in brackets.
1. In order to keep our environment ............ , we shouldn’t drop litter in public places. (pollute)
2. Don’t pump ............ into seas and rivers or it will pollute them. (sew)
3. Don’t throw away ............ bottles, papers, and glass. Take them to recycling centres. (use)
4. If we keep on ............ the air, more people will suffer from respiratory diseases. (pollution)
5. The local authorities have received many letters of ............ about the industrial wastes from that factory. (complain)
II. Complete the sentences with the correct form of the words in brackets.
1. Ba was ............ ill right after eating those ............ mushrooms. (serious / poison)
2. ............ are interested in the protection of the environment. (conserve)
3. Without ............ , some people wouldn’t catch fish. (electric)
4. Shhh. Listen ............ to the conservationist teaching us how to protect the environment. (care)
5. What is responsible for the ............ problems in your city? (environment)
III. Complete the sentences with the correct form of the words in brackets.
1. Make sure the use of ............ is not harmful to farm workers’ health. (pest)
2. ............ ! You have successfully held the clean-up campaign. (congratulate)
3. Use public transport or we won’t ............ pollution. (minimum)
4. If ............ continues, there will be no forest left ten years from now. (forest)
5. The rising level of air pollution has caused concern among ............ . (environment)

1.Phong/tend/go/countryside/weekend/have/rest.

2.life/countryside/quite/peaceful.

3.It/interseting/walk along/paths/enjoy/fresh air/night/moonlight

4.People/countryside/friendly/hospitable/people/city.

5.Life/countryside/today/much/good/than/used/be/long time ago.

6.Remote villages/our country/completely/supplied/electricity/already.

7.Nowadays/people/countryside/have/lot/chance/pursue/interests.

8.Living/countryside/help/people/good health/greater/longevity