cherry7girl
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some populations of flies are becoming resistant to insecticides intended to kill them.
Scientists developed a method for finding out whether a fly was carrying a recessive allele, r, that gives resistance to an insecticide. The dominant allele, R, of this gene does not give resistance.
The scientists:
• crossed flies with genotype RR with flies with genotype rr
• obtained DNA samples from the parents and offspring
• used the same restriction endonuclease enzymes on each sample, to obtain DNA fragments.
Explain why the scientists used the same restriction endonuclease enzymes on each DNA sample.

answer:
Cut (DNA) at same (base) sequence / (recognition) sequence;
Accept: cut DNA at same place
(So) get (fragments with gene) R / required gene. Accept: ‘allele’ for ‘gene’ / same gene

i dont understand how the same enzyme can be used for all the dna samples as wouldn't each sample be different/not complimentary?
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Amarachi IB
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i think it would work because the substrate is the same (the DNA) but the DNA samples just have different base sequences. so they would be complimentary with the enzyme because the enzyme is complimentary to DNA not just DNA with a specific base code. if that makes sense
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cherry7girl
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(Original post by Amarachi IB)
i think it would work because the substrate is the same (the DNA) but the DNA samples just have different base sequences. so they would be complimentary with the enzyme because the enzyme is complimentary to DNA not just DNA with a specific base code. if that makes sense
aaa i dont rly get that because wouldn't the differing base sequence change the chemical properties of each dna sequence?
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Amarachi IB
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(Original post by onedance1)
aaa i dont rly get that because wouldn't the differing base sequence change the chemical properties of each dna sequence?
no i dont think different base sequences would change it. its like when the DNA helicase enzyme un-zips DNA, it dosen't matter what type of DNA it is it is always complimentary and can un-zip it no matter the base sequence.
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cherry7girl
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(Original post by Amarachi IB)
no i dont think different base sequences would change it. its like when the DNA helicase enzyme un-zips DNA, it dosen't matter what type of DNA it is it is always complimentary and can un-zip it no matter the base sequence.
ohh i see, so basically there's a designated recognition site for the where the recessive allele would be, and therefore the enzyme cuts in the same site for every sample?
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Amarachi IB
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(Original post by onedance1)
ohh i see, so basically there's a designated recognition site for the where the recessive allele would be, and therefore the enzyme cuts in the same site for every sample?
yea basically
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macpatgh-Sheldon
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Good morning and Hi (why only one dance? I suppose COVID-19 has affected your fitness !),

Ok a little more explanation for your Q.
The scientists are trying to see if a particular gene is present or not in some samples. When we use a restriction endonuclease to break the bond between adjacent base pairs, THIS RESTRICTION ENZYME WILL BE SPECIFIC FOR THE BOND BETWEEN TWO SPECIFIC BASES e.g. one restriction enzyme could break A-A, another could break C-T, etc. you ask "But the bonding is always A-T and C-G, isn't it?) Good Q, young lady - however, we are talking about bonds between bases in the same chain NOT THOSE BETWEEN COMPLIMENTARY base pairs in TWO chains, yeah?

Ok when we want to identify a gene, if we sequentially break bonds between SPECIFIC BASES, then we will be left with IDENTICAL fragments after a number of cleavages if two sections of DNA had been originally identical, with me?

In this way, we can determine the complete base pair sequence of any DNA or fragment. Happy with that? Yes, I can see a smile just sprouting!

Be safe!
M.
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cherry7girl
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(Original post by macpatgh-Sheldon)
Good morning and Hi (why only one dance? I suppose COVID-19 has affected your fitness !),

Ok a little more explanation for your Q.
The scientists are trying to see if a particular gene is present or not in some samples. When we use a restriction endonuclease to break the bond between adjacent base pairs, THIS RESTRICTION ENZYME WILL BE SPECIFIC FOR THE BOND BETWEEN TWO SPECIFIC BASES e.g. one restriction enzyme could break A-A, another could break C-T, etc. you ask "But the bonding is always A-T and C-G, isn't it?) Good Q, young lady - however, we are talking about bonds between bases in the same chain NOT THOSE BETWEEN COMPLIMENTARY base pairs in TWO chains, yeah?

Ok when we want to identify a gene, if we sequentially break bonds between SPECIFIC BASES, then we will be left with IDENTICAL fragments after a number of cleavages if two sections of DNA had been originally identical, with me?

In this way, we can determine the complete base pair sequence of any DNA or fragment. Happy with that? Yes, I can see a smile just sprouting!

Be safe!
M.
one dance is actually a song! hehe and thank you so so much, that makes so much more sense
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