6.2 variation Flashcards
Define genotype.
The genetic makeup of an organism.
Define phenotype
The observable characteristics of an organism
What is a dominant allele?
An allele that will always be expressed.
What is a recessive allele?
An allele that will only be expressed if two copies are present.
What does homozygous mean?
The same alleles
What does heterozygous mean?
different alleles
What is continuous variation?
Variation that has no distinct categories and no limit to the value. It is mostly quantitative.
What are examples of continuous variation?
- Height
- weight
- heart rate
- finger length
- leaf length.
How can continuous variation be represented?
By a line graph.
What is discontinuous variation controlled by?
Few genes
What is continuous variation controlled by?
Multiple genes as well as the environment.
What is discontinuous variation?
Where there is a distinct categories with no in between values, the data tends to be qualitative.
Were examples of discontinuous variation?
- Tongue rolling
- eye colour
- fingerprints
- blood group.
How can discontinuous variation be represented
On a bar graph.
What does polygenic mean?
It is controlled by many genes.
What does monogenic mean?
It is controlled by one gene.
What are the causes of genetic variation?
- alleles
- mutations
- meiosis
- sexual reproduction
- chance
What is phenotypic variation affected by
The environment.
What is chlorosis?
When there is a lack of chlorophyll in a plant, it is caused by environmental factors such as a mineral deficiency, lack of light or viral infection.
What is etiolation?
Where plants grow abnormally long and spindly due to not enough light
How is genetic variation created in crossing over during meiosis?
The non sister chromatids twist around each other and swap allels. This means that they contain the same genes, but different alleles
How does independent assortment create variation in meiosis?
The chromosomes align along the metaphase plate randomly during metaphase. 1. from each pair is passed onto each daughter cell.
How is genetic variation created during random fertilisation?
Any sperm is able to fertilise any egg, which means each individual is unlikely to have the existed before or again.
What is monogenetic inheritance
Inheritance that it controlled by a single gene.