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The two strands of a DNA molecule can be split denatured) by heating. If a scien

ID: 212320 • Letter: T

Question

The two strands of a DNA molecule can be split denatured) by heating. If a scientist is careful and slowly raises the temperature, the DNA molecule will reach a point where the bonds between the two strands fail and the strands separate 16. Thinking about species X and Y, can you predict which one would have DNA that separates at a LOWER temperature? EXPLAIN your answer. Think about how the species DNA differ. Some thought questions. 17. Summarize the evidence and techniques of procedures that Watson and Crick used to deduce the double helix structure of DNA? 18. Each group member should describe in turn, the role of each of the key enzymes and proteins that help direct DNA replication? DNA Polymerase Primase Helicase Topoisomerase DNA Ligase

Explanation / Answer

16 ) - the main determinant Shall be the size of DNA and the level of compaction of DNA , longer the DNA and more levels of compaction ( as prokaryotes versus Eukaryotes ) , higher shaSh be the temperature required to denature it , and vice- versa .

17) - the double helical model of DNA was envisaged by multiple evidences such as , anti - parellel strands , Chargaff's experiments , X-RAY diffraction model developed by roslind Franklin , and analysing , collating data from other researchers like Robert Corey , Linus Pauling etc. And also from Maurice Wilkins. Putting the available data in coherent and plausible way to explain the observed charechterics , led to the development of double helical DNA model.

18) DNA polymerase - brings about elongation of primed strands , and also proof reads the errors , removes Primer sequence and adds deoxyribonucleotides in their place

Primase - starts the replication of strands by adding Ribonucleotides

Helicase - Unwinds the strands by breaking hydrogen bonds

Topoisomerase - prevents supercoiling of unwound DNA to allow unhindered replication

DNA ligase - joins the Okazaki fragments on the lagging strand