Question

Question 16 How many of each of the following are in this double-standed piece of DNA? TTCCGCGCACCAAGTT AAGGCGCGTGGTTCAA Phosphodiester bonds: Purines: Hydrogen bonds: 3' hydroxyl (OH) groups: G/C ratio:

Answer 1

Ans 1: Phosphodiester bonds: In DNA, phosphodiester bond ate formed between the OH group of phosphoric acid and CH₂ OH group of deoxyribose sugar by the removal of water. This is called as 3' -->5' phosphodiester bond as it denotes the phosphodiester bond between 3' - OH  of 1st nucleotide and CH₂OH of 5th carbon of deoxy ribose sugar.

Thus, phosphodiester bond connects two subsequent nucleotides.As can be seen from this picture

Formation of phosphodiester bond - p = 0 p =0 3 г 9. Он н 0-P=O Phosphodiester + H2O bond another chemical bond SCHZ ОН Н Он н.

Here in this given question, 16 nucleotide are present in the single strand (upper), suggesting 15 phosphodiester bonds are present which are connecting these nucelotides.

Since, 2 strands are given in the question, 15 X 2 = 30.

Can be seen from this image,

Marked in orange are phosphodiester bonds Date Page T-T-C-C-GG G C AC! Ch A G 14 TT A AGG-C-GEC-GTTEGGE ET CZAA

Therefore, 30 phosphodiester bonds are present in the given question.

Ans 2. I have written all explanation in this image, with the answer.

Ans 3: As we know, in double stranded DNA, Adenine in one strand forms 2 hydrogen bond with Thymine in another strand whereas Guanine in one strand forms 3 hydrogen bond with cytosine in another strand. As can be seen in this picture.

Purines – Nitrogenous bases having 2 rings i one hexagon and one pentagon Examples of furine are 3 MA Adenine (1) Guanine (G) > Thymine (1) and Cytosine (C) ave pyrimidines. They consist of only one hexagon ring. They are Lalo nitrogenous I bases, that make up Desa Aus (2) No. of Purines in this are - 16 (Including All A_and G. )counting showed in orange coole. TICC G C Ğ C Å CC À TI A A G G C G C G T G G T T C A A CS$canned with CamScanner

Adenine-Thymine base pair H -= 0 N = 7 Adenine (A) Thymine (T) Guanine-cytosine base pair CH 0---H2H 1 NGH---N 6C-H =Ć - Guanine (G) NFH---O cytosine (cCi

Marked in red are hydrogen bonds.

Total AT pairs in the given question are: 7

And one pair contains 2 hydrogen bonds, therefore, total hydrogen bonds in AT pair are : 7 X 2 = 14 hydrogen bonds.

Total GC pairs in this given in this given question are: 9

Therefore, as we know Number of hydrogen bonds in one GC pair are 3. Eventually Number of hydrogen bonds in total 9 GC pairs will be 9 X 3 = 27.

As we know now, total number of hydrogen bonds in this given question are are 14 + 27 is equal to 41 hydrogen bonds.

Ans 4. In DNA, two strands are there, the upper one which has polarity 3' to 5' and the lower strand which has complimentary polarity that is 5' to 3'. Generally the 3' group has free group hydroxyl group (3' - OH).

One strand has  only one free 3' hydroxyl group.

will get more clear, one you will look this picture

NHC N

Therefore, both the stand will have 2 free 3' - OH hydroxyl group.

Ans 5: GC ratio is the percentage of guanine and cytosine deciduous present in the overall DNA strand. In this given DNA strand total number of nucleotides are 32, out of which number of guanine and cytosine residues are 18.

GC ratio = G + C count/ A+ T + G + C count, multiplied by 100

G+ C count = 18

A + T + G + C count = 32

= 18/32

= 0.56 X 100

= 56%

I hope, you will not have any doubt further, and these answers will help you.