Evolution- 4.2- Comparative Genomics Flashcards
2.1- Comparative Genomics, 2.2- Phylogenetic Trees, 2.3- Mutation Rate
Describe the technique of DNA Hybridisation
- 2 sequences to be compared are isolated using a gene probe and enzymes.
- 2 strands are heated to separate strands.
- DNA is cut into smaller segments using restriction enzymes.
- The DNA from the two species is mixed and cooled, causing DNA to complementary base pair to form hybrid DNA.
- Strands reheated to determine ‘melting point’.
The higher a melting point the more closely related the two species are as more bonds between the nucleotide sequence of the two strands form.
What can the sequencing of common proteins, like cytochromes, reveal about species relationships?
The sequence of amino acids in proteins is determined by the DNA sequence. Greater differences in amino acid sequences indicate more differences in DNA, meaning species are less closely related. Fewer differences suggest the species are more closely related.
How does DNA–DNA hybridisation provide evidence of different species?
DNA–DNA hybridisation shows evidence of species differences when DNA samples from different groups only partially hybridise, indicating they are not fully complementary.
How is DNA sequencing, including rRNA gene sequencing in prokaryotes, used to compare species?
DNA sequencing can show distinctly different base sequences in DNA or rRNA at the same location, providing evidence of genetic differences between species.
What does a greater difference in amino acid sequences suggest about the relationship between species?
A greater difference in amino acid sequences suggests that the DNA sequences are more different, indicating that the species are less closely related.
What does partial hybridisation in a DNA–DNA hybridisation experiment suggest about two species?
Partial hybridisation suggests that the DNA sequences are not fully complementary, indicating that the species are genetically different.
In a phylogenetic tree, what does it mean if two species share a more recent common ancestor?
If two species share a more recent common ancestor, they have fewer genetic differences, indicating that they are more closely related.
How is mutation rate used as a ‘clock’ in evolutionary biology?
Since mutations accumulate at a relatively constant rate over time, knowing the mutation rate allows scientists to estimate the time since species diverged, acting as a molecular clock.
What does the accumulation of mutations over time indicate in terms of species relationships?
More closely related species will have fewer differences in their DNA sequences, as they have separated more recently from a common ancestor compared to distantly related species.
