Science

Plants and animal cells have a few things in common:

Cell membrane- Separates the contents of the cell and its surroundings. It controls the movement of substances like oxygen, glucose and carbon dioxide into and out of the cell.    Cytoplasm- Where many of the chemical reactions needed to carry out life processes take. It also contains organelles (tiny structures that carry out specific jobs.                                       Nucleus- An organelle that contains DNA, which is the genetic material. The nucleus also contros all the activities of the cell.                                                                                                   Mitochondria- Organelles in which respiration occurs (oxygen and glucose react ro release energy by the cell). They are very tiny and cannot be seen easily through a light microscope at low magnification.

Plant cells also have some other structures:

Cell wall- made of tough cellulose to support the cell and allow it to keep its shape.

Large vacuale- a space in the cytoplasm that is filled with cell sap and helps to support the plant by keeping the cells rigid.

Chloroplasts- organelles that contain chlorophyll, a green substance that absorbs light energy used in photosynthesis.

There are two strandds in 2 strands in a molecule of DNA that are cioled together to form a spiral known as a double helix. The 2 strands are linked together at regular intervals by chemicals called bases.

The bases always pair up the same way because of the shapes of each of the molecules.

Adenine (A) pairs with Thymine (T), A=T

Cytosine (C) pairs with Guanine (G), C=G

These matches are known as Complementary base pairs. They are joined together by hydrogen bonds. The order of the bases in DNA

In London, Wilkins and Franklin were studying the structure of DNA using X-rays. Franklin directed beams of X-rays at purified DNA and used photo to record how the moldecule scatered the X-rays. From the patterns she could work out how the groups of atom in the DNA molecule were arranged.

In Cambridge, Watson and Crick were trying to build a 3D molecular model of DNA using the data from a number of other scientists. They used X-ray results from the London team including some of Franklin's best X-ray images that Wilkins had shown them without Franklin's permission.It was the detail in her images that gave watson and Crick the clues they needed to build their double helix model.

Scientists can remove a gene from one organism and insert it into the DNA of another organism.

Insulin used to be extracted by dead cattle and pigs but insuling from GM bacteria can be used by vegans. 

The insulin is removed from a human chromosome using a restriction enzyme and then is inserted into a plasmid using DNA ligase. The Plasmid is then put back into a bacterium to reproduce.

Advantages of GMOs (Genetically Modified Organisms)

• It means humans can get vital vitamins/ elements. e.g Golden rice is normal rice buy has 2 extra genes so that they also have beta-carotene in the grains. Beta-carotene is needed by humans to produce Vitamin A. Lack of Vitamin A can cause death.
• In the past insulin was reproduced from dead cows and pigs, but new genetically modified insulin means it can be reproduced from bacteria so vegans can now have this.
• Some plants can be made herbecide resistant. This reduces amount of crop spraying as a heavier herbecide can be used.

Disadvantages of GMOs

• The bacteria produce insulin that is slightly different. There are minute differences and it does not suit everyone.
• Some people are concerned that Golden rice will cross breed with wild rice and contaminate wild rice DNA.
• Some people think GMOs may harm people (no evidence)
• It can be expensive to buy and some may not produce fertile seeds so you woul have to keep buying new seeds each year.
• Herbecide resistant plants may crossbreed with weeds and so this may cause herbecide resistance weed.

1. parent cell
2. chromosomes make identical copies of themselves
3. they line up along the centre
4. they move apart
5. two daughter cells form with identical chromosomes to the parent cell

1. parent cell

2. chromosomes make identical copies of themselves

3. Similar chromosomes pair up

4. Sections of DNA get swapped

5. Pair of chromosome divide

6. Chromosomes divide.

Mitosis is simple cell division, ending up with two identical cells, each with both pairs of every gene.

Meiosis is cell division for gametes (sex cells). This is a two step process, and the four cells that remain each have half the normal cells, so that when the gametes fuse at conception, there will be a new organization of DNA, from both parents.

1a. Sheep A: A body cell is taken from sheep A, DNA is extracted

1b. Sheep B: Egg cell is taken from Sheep B, Nucleus is removed

2. DNA from Sheep A fused with egg cell from Sheep B

3. Fused cell develops into embryo which is placed in uterus of foster mother (Sheep C)

4. Lamp is clone of Sheep A

The nucleus of a bidy cell of the animal to be cloned is transferred into an enucleated egg cell(one that has had its original nucleus removed) .The cell is them stimulated to start dividing to form an embryo.This is implanted into the uterus (womb) of a surrogate mothereho is different individual to the parent. Here it will grow and develop into a new individual

The clones grow older much more quickly than normal and die young.

It is useful to make a genetically identical copy of an adult organism that has desirable characteristics. E.g. bulls whose sperm produces high quality calves are valuable so worth cloning. Cloning it also used to produce copied of individuals with a genetically engineered trait like cows engineered to produce human insulin in their milk because it means the offspring will also have these traits.