DNA structure. I need help with part 2: building a DNA strand For question 2 a,
ID: 209462 • Letter: D
Question
DNA structure. I need help with part 2: building a DNA strandFor question 2 a, b, b
Part 2. Building a DNA strand DNA nucleotides are connected together to build a DNA strand. A DNA strand has two ends. The 5' end has a free phosphate group; the 3' end has a free -OH group. Each new nucleotide has its phosphate group added to the -OH group on the 3' end of the DNA strand. Refer to the drawing of the DNA strand (to the right). a. On the drawing, label the 5' end. Label the 3' end. b. Label the nitrogenous bases with the appropriate letters (A, T 2. C, or G). On the drawing, add a thymine to make a 5-nucleotide strand. The sequence of this strand will be 5'-TGCAT-3'. b.
Explanation / Answer
a. The upper end in the drawing is 5' end and lower end is 3' end. The 5' end has a free phosphate (P) group while 3' end has a free hydroxyl (-OH) group. It is clear in the drwaing that phosphate group is free (not bonded with next nucleotide) at the upper end while hydroxyl group is free (not bonded with next nucleotide) at lower end.
b. The nitrogenous bases in the drwaing from upper to lower (5' to 3' end) are as follows: 5'-TGCA-3'
b. The thymine will be added at the lower end (3' end). The phosphate group of thymine will be added to the free hydroxyl group (-OH) of adenine. Thus the sequence of this strand will be 5'-TGCAT-3'.
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