Biology - Variation, Reproduction and New Technology

We have charecteristics that are inherited by parents. This is through information being carried by genes which are passed onto you during fertilisation with the sex cells (gametes). The genes are in pairs, one gene from both the mum and dad.

The genteic information is carried through the nucleas which have chromosomes and each organism has a different amount (humans have 46). Chromosomes are made up of DNA, which is a special chamical.

The DNA is made up of two strands that twist together making a spiral. 

Each chromosome contains thousands of genes which are the units of inheritance. This will determine what an organism is like (size, shape, colour). They control the charecteristics by controlling all enzymes. 

Scientist think that there are from 20,000 to 25,000 genes in a human body.

Asexual reproduction is when there is no joining of sex cells or variety of offspring. The offspring is defined as the clone as it has the same genetic material to the parent. Some small plants and animals do it as well as the cells in bodies.

Sexual reproduction involves to parents, a male and female with two sex cells. The offspring will inherit both genes and will not look like wither of them, thy will be unique.

Sexual reproduction introduces variety which is a great advantage because it makes it likely that some of the offspring will survive difficult conditions using mutations.

The basic characteristics of an organism is determined by the genes inherited. However, some of the characteristics are completely due to the environment, such as scarring.

Identical twins brought up together will show smaller differences as adults than identical twins brought up apart, or non identical or non-twin siblings.

To clone a plant a farmer must take a few cuttings of the plant and keep it in the right conditions (a moist atmosphere), new roots and shoots form. 

By using this method you can produce plants quickly and cheaply. Many farmers will use hormone rooting powder to encourage the cuttings to grow.

Another way to clone a plant is through tissue culture. It is more expensive but allows you to make thousands of plants to one plant tissue.

The first step is to produce a small group of cells from the plant using hormones of a plant, then using the right hormones and conditions, each cell will form a tiny, new plant. 

This guarantees thousands of plants identical to the plant you want to clone.

Using embryo cloning your best cows can produce more top cows each year.

You firstly give a top cow lots of hormones so it produces lots of eggs and fertilise the eggs from a top bull. At this stage, all cells of the embryo can still form cells needed for a cow.

These cells are split so that they each form another embryo which are identical to one another. Then identical calves are born but are not biologically related to their mothers.

Even though this is expensive, a cow can produce 8-10 calves in her life time when she can normally only produce one or two.

Cloning a cell from an adult is easy but to get it to form an embryo, which is called adult cell cloning, is very difficult.

The steps involved are;

• The nucleus is removed from an unfertilised egg cell and a nucleus is removed from an adult body cell.
• The nucleus of the adult cell is transplanted into the empty egg cell.
• The new cell is given an electric shock to start the division which contain the same genetic information as the adult cell.
• When the embryo forms a ball of cells it is transplanted into a womb to carry on developing.

The advantages are that this method could save animals from extinction and to reproduce prized pets.

Cloning could also be abused and reduces variety in a population.

Genetic engineering is the changing of genetic material of an organism. You do this by taking a gene from one organism and putting it into the genetic information of a different organism.

The genes of one organism can be transferred to a plant or animal at an early stage so it develops with the new characteristics. 

Genetically engineered bacteria can make the proteins we need in the exact amounts and in a very pure form. We can use genetic engineering to improve growth rates of plants and animals, so there can be a much bigger yield.

They can also be designed to live in hot, cold, dry conditions and to produce their own pesticides. Genetic Engineering can help genetic diseases.

The disadvantages of genetic engineering are insects becoming pesticide-resistant because of a diet on pesticide forming plants. Also, GM crops can become infertile so you would have to buy new seeds and there could be a risk of eating GM foods.