Genetics Question Help Please!

[Strag]

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If a 28 base-pair segment of double-stranded DNA contains 10 adenine residues, how many guanine residues are there?

is it 7 or 10?

28 to 14 and each has 7. Or 10 adenine 10 guanine.

 

[JamesBourne]

If a 28 base-pair segment of double-stranded DNA contains 10 adenine residues, how many guanine residues are there?

is it 7 or 10?

28 to 14 and each has 7. Or 10 adenine 10 guanine.

I have seen a similiar question from the destroyer, and know that A+G = T+ C. Since the number of A and T are the same, we have 10 adenine residues, and 10 thymine residues, which leaves us with 8 remaining? I don't exactly understand the use of wording residues here, but If I am guessing right, guanine should be 4 because 8 remaining is equally divided between guanine and cysteine. Btw, where did you get this question?

 

[Kahr]

I'd also like to know where this is coming from.

My take:

28 base pairs; each pair is either a A-T or a G-C

If we assume saying adenine residue is the same as saying adenine, then having 10 adenine residues, we must have 10 thymine residues, and when they pair, 10 base pairs of A-T.

28 base pairs - 10 base pairs = 18 base pairs

So there must be 18 guanine and 18 cytosine to pair up to form our remaining 18 base pairs, no?

 

[amalgamgrillz]

I'd also like to know where this is coming from.

My take:

28 base pairs; each pair is either a A-T or a G-C

If we assume saying adenine residue is the same as saying adenine, then having 10 adenine residues, we must have 10 thymine residues, and when they pair, 10 base pairs of A-T.

28 base pairs - 10 base pairs = 18 base pairs

So there must be 18 guanine and 18 cytosine to pair up to form our remaining 18 base pairs, no?

Agreed.👍

 

[JamesBourne]

I'd also like to know where this is coming from.

My take:

28 base pairs; each pair is either a A-T or a G-C

If we assume saying adenine residue is the same as saying adenine, then having 10 adenine residues, we must have 10 thymine residues, and when they pair, 10 base pairs of A-T.

28 base pairs - 10 base pairs = 18 base pairs

So there must be 18 guanine and 18 cytosine to pair up to form our remaining 18 base pairs, no?

Thanks for better explanation, get it now =)

 

[AmpedUp]

Chargaff's Rule:

A + G = C + T

(I always think of it as A + G + C + T = # total number of base pairs or 1 if percentages are given)

A = 10, which means it's complementary residue, T, has 10 base pairs. Therefore, a total of 20 bases have been used between A and T, and you have 8 pairs between C and G (each with 4 base pairs).

Answer: 4 G base pairs.

 

[Kahr]

Chargaff's Rule:

A + G = C + T

(I always think of it as A + G + C + T = # total number of base pairs or 1 if percentages are given)

A = 10, which means it's complementary residue, T, has 10 base pairs. Therefore, a total of 20 bases have been used between A and T, and you have 8 pairs between C and G (each with 4 base pairs).

Answer: 4 G base pairs.

You just subtracted 20 bases from 28 base-pairs (28 base pairs = 56 bases), this wouldn't turn into 8 pairs remaining.

Then you say 8 pairs between C and G, which equals 16 bases (8 of each). How does 36 bases (16 + 20) = 28 base pairs?

Finally, you answer 4 G base pairs, but the question is about the number of G bases. Also, Chargaff's rule uses bases not base pairs.

 

[chance8]

I agree with Kahr.

28 base pair-10 A thus 10 T.

28-10=18 C-G basepairs, i.e. 18 G and 18 C.

 

[AmpedUp]

You just subtracted 20 bases from 28 base-pairs (28 base pairs = 56 bases), this wouldn't turn into 8 pairs remaining.

Then you say 8 pairs between C and G, which equals 16 bases (8 of each). How does 36 bases (16 + 20) = 28 base pairs?

Finally, you answer 4 G base pairs, but the question is about the number of G bases. Also, Chargaff's rule uses bases not base pairs.

oops! my bad.