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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