AQA BIOLOGY B14 - VARIATION AND EVOLUTION

Nature

Nature is genetic variation, they are basic characteristics of genes inherited, genetics bring variation. 

Nurture

Nurture brings in environmental variation, the environment can chage how you look e.g. scars. Plants can be genetically identical and some of them can be deprived of divergent things like water or C02 so it wont be able to reach its genetic potential, therefore they will look different. 

Combined causes of variety: 

genetic+environmental, Genetically you could be fat but environmentally you do not eat enough.

Investigating variety:

Genetically identical plants can be put into different conditions to see how environment effects it. Identical twins come from the same fertilised egg, this can be investigated by observing different types of twins

Why do people choose selective breeding?

-To produce more animals which make more meat or milk

- To make plants which are resistant to diseases so food crops arent infected

- To make bright large scented flowers

- Domestic dogs and cats which have a gentle nature

Limitations of selective breeding:

It reduces the alleles in the population this reduces variation, if one dies due to climate change, they will all die. Theres also a problem in inbreeding, this can cause diseases and infections. 

How is it done?

1- Enzymes are used to isolate and 'cut out' the required gene from an organism

2- Gene inserted into a vector with more enzymes inside it. Vector is usually a plasmid or virus. 

3- Vector is then used to insert gene into required cells such as bacteria, fungi, plants or animals. 

4- Genes transferred to cells at an early stage so the organism develops with th new desired characteristics. 

5- In plants the desired characteristics are out into the meristems of the plant to produce identical clones. 

How is it done?

1- small tissue sample is taken from plants

2- tissue grown in agar with combination of nutrients and plant hormones (forms a big mass of tissue called a callus)

3- different mixture of hormones and nutrients resulting in divergent plantlets

4- Identical plants formed

How is it done?

1- Fertility hormones given to a top quality cow and produces eggs

2- fertilise the eggs with sperm from a good animal. Then it is washed out of the uterus gently. 

3- Early embryo of clustered identical cell divides embryo into severa individual cells

4- Each cell grows into an identical embryo

5- Transfer embryos to the host mothers which have been given hormones

6- Cloned animals are born but not biologically related to them. 

How is it done?

1- Nucleus is removed fro an unfertilised egg cell

2- Nucleus is taken from adult body cell, e.g skin cells of another individual of the species.

3- Nucleus from the adult cell is inseted into the empty egg cell

4- New egg cell is given an electric shock to start dividing to form embryo cells which contains some gentic info as original adult 

5- When embryo has developed in a ball of cells it is inserted back into womb of female to continue its development