Genetic variation in populations Flashcards
what is population genetics the study of?
Genetic variations in populations = Mendelian genetic variants
+
forces that act on this variation = Darwin’s theory of natural selection
Name 4 ways genetic variation can be studied
Quantitative traits e.g. height, weight
Visible polymorphisms
Protein polymorphisms
DNA variation
How are quantitative traits used to study genetic variation?
Effects of individual genes cannot be seen- as multiple genes and environmental factors are acting on one trait
Evidence e.g. plant height
- off-spring would have heights similar to the original parental plant height mean
- variation in height suggests not just a genetic influence
what is a protein polymorphism ?
+ how is it carried out?
= variation in amino acid sequence of a polypeptide between individuals in a population
- done via sequencing the alleles and then determining amino acids via genetic code
- early studies used electrophoresis
Define: allozyme
different form of an enzyme
Describe the process of starch gel electrophoresis
+ what does it involve
Involves separation of alleles of allozymes on the basis of their charge
1. Organism crushed and placed on gel
2. Current run through gel
3. Proteins move through gel based on size + charge
4. Proteins are then stained
What are 2 different types of allozymes and how are they different?
Slow + fast type:
depends on how fast they pass through the gel
What is a visible polymorphism ?
+ example
= alternative phenotype in a population of a species- 2 or more different alleles exist at 1 gene locus
e.g. snail shell pattern + colour
- This variation has been retained due to negative frequency dependent selection
= no predominant form as birds will predate on most common form until another form becomes more common
After the proteins have been stained during electrophoresis, what do the different band patterns mean?
one band = homozygous
two band = heterozygous
Describe how DNA variation is studied nowadays
and how has it changed ?
- Copies of genes were cloned on bacterial plasmids and the inserts were then sequenced
Nowadays: Polymerase Chain Reaction has specific primers that target specific sections of DNA
1. Primer on either side of DNA that target a gene amplified in the middle:
- X + Y chromosome + mitochondrial DNA = sequence PCR directly
- autosomal genes = clone DNA from PCR then it is sequenced
= Copies of DNA sequence from gene of interest
Name the 2 types of DNA changes and how are they different ?
Synonymous = base can change but resulting amino acid stays the same due to degenerate code
Non-synonymous = base change results in amino acid change
Name the 2 different categories of bases and which bases go in which category?
Purine = adenine, guanine
Pyrimidine = cytosine, thymine, uracil
Name 2 types of mutational effect + how are they different ?
Transitions = mutation that changes a purine to a purine e.g. A to G or a pyrimidine to a pyrimidine e.g. C to T = most common
Transversions = changes purine to a pyrimidine and vice versa
Name a measurement of diversity
Nucleotide Diversity
Which has higher levels of genetic variation:
Unicellular vs multicellular
Invertebrates vs vertebrates
Unicellular
Invertebrates + plants
