'Science has been used to solve problems in the investigation of evolutionary
relationships between humans and other primates, and so has provided information of interest to society.'
Justify this statement in terms of the scientific knowledge behind DNA-DNA hybridisation AND karyotype analysis. (7 marks)
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→ Using comparative morphologies limits our ability in determining relationships between humans and other primates. Sometimes morphologies seem very different, yet the changes or modifications required to achieve those differences might be small in number or too simple.
→ Using genetic evidence gives a much more accurate picture.
DNA-DNA Hybridisation
→ Can be used to show how genetically similar two species are.
→ DNA from a human and a chimpanzee (other primate) can be tested for melting point. Then it can be melted into single strands. The single strands are combined into hybrid DNA, in which some hydrogen bonding between base pairs does not happen because they are not complementary.
→ The lower the hybrid DNA M.P. is compared to the original DNA is a measure of how similar the original DNA was.
→ When the DNA is similar the two species are seen to be close in evolutionary terms.
Karyotype Analysis
→ Involves using a chemical to kill a cell during cell division when the chromosomes can be seen individually.
→ Photos are taken and the chromosome pictures arranged in pairs of increasing size. This picture of all the chromosomes in the genome is a karyotype.
→ Comparing the number, size, shape and banding pattern of chromosomes allows scientists to observe differences between species.
→ The fewer differences between karyotypes, the closer the species are in evolutionary terms.
→ People are interested to study our closest living relatives, as it helps us to understand where we have come from. It helps us to understand ourselves as a species when we can identify our closest living relatives and see our unique or common features and behaviours. DNA-DNA hybridisation and karyotype analysis help scientists to accurately achieve this knowledge.
→ Using comparative morphologies limits our ability in determining relationships between humans and other primates. Sometimes morphologies seem very different, yet the changes or modifications required to achieve those differences might be small in number or too simple.
→ Using genetic evidence gives a much more accurate picture.
DNA-DNA Hybridisation
→ Can be used to show how genetically similar two species are.
→ DNA from a human and a chimpanzee (other primate) can be tested for melting point. Then it can be melted into single strands. The single strands are combined into hybrid DNA, in which some hydrogen bonding between base pairs does not happen because they are not complementary.
→ The lower the hybrid DNA M.P. is compared to the original DNA is a measure of how similar the original DNA was.
→ When the DNA is similar the two species are seen to be close in evolutionary terms.
Karyotype Analysis
→ Involves using a chemical to kill a cell during cell division when the chromosomes can be seen individually.
→ Photos are taken and the chromosome pictures arranged in pairs of increasing size. This picture of all the chromosomes in the genome is a karyotype.
→ Comparing the number, size, shape and banding pattern of chromosomes allows scientists to observe differences between species.
→ The fewer differences between karyotypes, the closer the species are in evolutionary terms.
→ People are interested to study our closest living relatives, as it helps us to understand where we have come from. It helps us to understand ourselves as a species when we can identify our closest living relatives and see our unique or common features and behaviours. DNA-DNA hybridisation and karyotype analysis help scientists to accurately achieve this knowledge.