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DNA hybridisation is a molecular technique used to determine the evolutionary relationships between species - VCE - SSCE Biology - Question 6 - 2017 - Paper 1
Question 6
DNA hybridisation is a molecular technique used to determine the evolutionary relationships between species. DNA is extracted from each species and cut into fragment... show full transcript
Worked Solution & Example Answer:DNA hybridisation is a molecular technique used to determine the evolutionary relationships between species - VCE - SSCE Biology - Question 6 - 2017 - Paper 1
Step 1
Outline the steps involved in the DNA hybridisation technique following the extraction and cutting of DNA.
Answer
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Extracting DNA: Begin by obtaining samples of DNA from the species of interest. This is commonly done through cell lysis, where the cellular membrane is broken down to release the DNA.
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Cutting DNA into Fragments: Use restriction enzymes to cut the extracted DNA into smaller, manageable fragments. These enzymes recognize specific sequences and create double-stranded breaks, leading to uniform fragments.
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Denaturing DNA: Heat the cut DNA fragments to separate the two strands, creating single-stranded DNA. This process, known as denaturation, is crucial for hybridisation.
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Hybridisation: Mix the single-stranded DNA fragments from different species together. During this process, complementary strands will bind to each other, forming double-stranded hybrids.
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Cooling and Ligation: Gradually cool the mixture to allow for optimal binding of the DNA fragments. After hybridisation, ligation may occur, where the fragments are permanently joined.
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Analysis: Finally, analyze the extent of hybridisation through techniques such as gel electrophoresis or measuring fluorescence intensities, which will provide insights into the evolutionary relationships between the species.
Step 2
How does the technique of DNA hybridisation enable scientists to determine the evolutionary relationships between species?
Answer
DNA hybridisation allows scientists to assess the degree of genetic similarity between different species. By evaluating how well the DNA strands from different species bind together, researchers can determine the extent of complementary base pairing.
The temperature at which the hybridised DNA becomes single-stranded indicates the strength of the bond; a higher melting temperature implies greater similarity and, thus, a closer evolutionary relationship. This technique enables scientists to construct phylogenetic trees and understand evolutionary pathways.