18.2 - Variation In Phenotype Flashcards
True of false: ‘Within a population, all members have the same genes.’
True
What are the 3 sources of genetic variation
1) mutation — sudden change in gene/chromosomes. May be inherited by next generation
2) Meiosis — all gametes are different due to random assortment of homologous parts of chromosomes in prophase 1
3) Random fertilisation of gametes — new combination of alleles in offspring
How do sexually reproducing organisms, increase variation
- mutation
- meiosis
- random fertilisation of gametes
Describe the relationship between variation (traits) and the environments influence
- if the trait is caused by one gene = environment has very little influence
- BECAUSE: alleles for a gene represents discrete categories, e.g. green eyes, or blue eyes or brown eyes
- however….
- polygenetic variation (i.e. polygenes are when many genes influence a trait) = highly influenced by environment
- genetically you have a predetermined maximum height, however if you don’t have the right nutrients from your diet = you don’t reach your max height
If we measure the variation between individuals as a result of polygenes, what type of graph do we get
- normal distribution curve
Because in most cases variation is due to the combined effects of genetic differences and environmental influences, what do we need to be careful of?
Any conclusions that are drawn are usually tentative and should be treated with caution
State how genetic variation is increased in asexually reproducing organisms
Mutation only
In the following list of statements, determine whether each refers to variation due to genetic or environmental factors:
a) It can be represented by a line chart.
b) It is usually controlled by a single gene.
c) It can be represented as a bar chart.
d) A mean can be calculated.
e) An example is the length of the body in rats.
A) environmental
B) genetic
C) genetic
D) environmental
E) environmental
