6.2.1(Genetic Variation)

State the 2 factors which affect genetic variation

• Genetic factors

• Environmental factors

State the 2 genetic factors which can lead to genetic variation

• Sexual reproduction

• Mutagens

State some physical mutagens which can increase the rate of mutation

• X-rays

• Gamma rays

• UV light

State some chemical mutagens which can increase the rate of mutation

• Tobacco smoke

• Aromatic amines

• Reactive oxygen species

State some biological mutagents which can increase rate of mutation

• Food contaminations

• Alcohol

• Some virsuses

State the 2 different types of variation

• Continous

• Discontinuous

Describe the properties, give examples and state what continous variation is controlled by

• Properties:

  • No distinct categories

  • No limit on the value

  • Tends to be quantitative

• Examples:

  • Height

  • Weight

  • Heart rate

• Controlled by:

  • A lot of genes and the environment

Describe the properties, give examples and state what discontinuous variation is controlled by

• Properties:

  • Distinct categories

  • no in between categories

  • tends to be qualitative'

• examples:

  • tongue rolling

  • finger prints

  • eye colour

  • blood groups

• controlled by:

  • A few genes

Describe and explain how sexual reproduction can lead to genetic variation

• During meiosis, in prophase 1, crossing over occurs, which involves alleles from the 2 sister chromatids switching, which increases genetic variation in gametes

• During meiosis, in Metaphase 1 and 2, independent assortment occurs, which is where the chromatids and sister chromatids are randomly aligned at the equator of the cell, which causes them to go to random nuclei, this increases genetic variation in gametes

• Random fusion of gametes during fertilisation increases genetic variation

State 2 environmental factors which lead to genetic variation

• Etiolation in plants

• Diet in animals

Describe what is meant by etiolation

• Plants grow abnormally long and spindly as they are not getting enough light

Describe how other environmental factors can lead to variation

• Factors such as temperature can lead to the expression of certain genes which cause change in colour of fur or skin in the animal