DNA Question (T/F) - (Oct/19/2009 )

1. The problem statement, all variables and given/known data

Which of the following are true statements ?

a) DNA is composed of a series of necleotides, each of which is made up of a phosphoric acid unit, a sugar unit and a cyclic nitrogen base.

In DNA the base must be either alanine, threonine, glutamine, or cysteine.

c) In the three-dimensional Watson-Crick structure of DNA, two polynucleotide DNA strands wind around each other to form a double helix.

d) The DNA sequence of base pairs in the nucleus of a cell represents the genetic code that controls inherited characteristics.

e) Genes are the sequence of bases in DNA that are the code for the synthesis of a single protein within the body.

2. The attempt at a solution

NOT SURE BUT :
a) It can not be a because it should be phosphate group instead of cyclic nitrogen base
I thought it should be correct, since DNA bases are adenine (A), guanine (G), thymine (T), and cytosine ©
c) It's true that the two polynucleotide chains in DNA molecule.
d) the bases are unique, that tells the characteristics
e) I'm not sure, but I thought that it should be since genes are code for synthesis of proteins.

I tried bcde and bcd but it's incorrect. Please help, thank you!

a) is true, b) is false (those are amino acids), e) is false because some genes code for more than one protein.

strwberry on Oct 19 2009, 05:21 PM said:

I think a is true and b is false.

a: DNA is composed of dNTPs which are composed by a sugar (deoxyribose), a base (the cyclic nitrogen base: A, T, C or G) and a phosphate group (the phosphoric acid).

b: alanine, threonine, glutamine and cysteine are all aminoacids not bases. The DNA bases as you said are: Adenine, Thymine, Cytosine and Guanosine, so not sure why you thought b might be true.

c: true
d: true... although it could also be false (if being petty) as it does not include mitocondrial DNA which also codes for inherited characterisitcs
e: false. 1 gene is not always 1 protein as there can be splicing variants and things like that.

So my bet is that A and C are definitely true, B and E are definitely false... and I have my doubts about D.

Hope this helps

I tried c, ac, acd, cd they all are wrong =(
Thanks for helping though.

Should have tried acde...