Genetic Variation and its Control

Offspring resmeble their parents because they conain genetic information passed onto them by their parents.

Chromosomes and genes

• Chromosomes, found in the cell necleus contain many genes. 
• A gene is a section of DNA, which carries coding for a particular protien. 
• Different genes control the development of different characterisitcs of an organism. 
• Many genes are needed to carry all the genetic information for a whole organism.

Number of genes and chromosomes varies from species to species. Humans have 46 choromoes that carry around 30,000 genes in each cell. 

Genetic Factors

Although individuals of a species look similar, they are not usually idenitical these differences are calling variation. 

Inherited Variation

Variation due to genetic causes is inherited variation...

...For example, children usually look a little like their father, and a little like their mother. But will not look identical to either of their parents. As they get half of their inherited factors from each parent. 

• Eye colour 
• Hair colour
• Skin colour
• Lobe/Lobeless ear

Enviromental Factors

Characteristics of animal and plant species can be affected by such factors...

• Climate 
• Diet
• Accidents
• Culture 
• Lifestyle

E.g- Eat lots you will become heavier/Eat less skinnier, A plant in the shade will grow taller to get light

• Your language 
• Your religion
• Flower colour in hydrangeas (as these plants produce blue flowers in acidic soil and pink flowers in alkaline soil)

Combined genetic and enviromental factors

Some features vary due to a combination of the two factors.

E.g Identical twins inherit exactly the same genetic information from their parents. But if you take a pair of twins and twin A has eaten more than twin B, twin A is likely to end up heavier.