DNA structure 2

Question 1

are the building blocks of nucleic acids

Answer 1

Nucleotides

Question 2

Nucleotides are the building blocks of nucleic acids and consists of 3 components:

Answer 2

a nitrogenous base, pentose sugar and a phosphate group.

Question 3

Two types of nitrogen bases are found

Answer 3

purines and pyrimidines

Question 4

Purines

Answer 4

Double ringed

adenine (A) and guanine (G)

Question 5

Pyrimidines

Answer 5

single ringed

cytosine (C), thymine (T) and uracil (U).

Question 6

The base T, however, is only ever found in

Answer 6

DNA, while RNA has U in its stead

Question 7

The pentose sugars from which DNA and RNA are made-up of are also different, resulting in their different names

Answer 7

RNA contains ribose, while DNA is made-up of deoxyriboses.

Question 8

Difference between ribose and 2-Deoxyribose?

Answer 8

Ribose has an OH on carbon 2 and deoxyribose only has an H

Question 9

Why 2-Deoxyribose

Answer 9

Carbon 2 has hydroxyl group replaced by a H atom

Question 10

Nucleoside

Answer 10

nitrogen base plus pentose sugar

Question 11

Nucleotide

Answer 11

Nucleoside + a phosphate group

Question 12

Depending on the amount of phosphate groups that are attached to the nucleoside (1,2 or 3 respectively), the molecule can be called a…

Answer 12

nucleoside monophosphate (NMP)
nucleoside diphosphate (NDP) 
nucleoside triphosphate (NTP).

Question 13

Polynucleotide

Answer 13

Nucleotides are joined to each other by a phosphate group linking the two sugars

The joining of two nucleotides forms a dinucleotide. Following the same logic trinucleotides, oligonucleotides (less than 30 nucleotides) and polynucleotides (more than 30) are formed.

Question 14

Link between two nucleotides (polynucleotide)

Answer 14

phosphodiester bond

Question 15

“Normal” DNA is made-up of extremely long

Answer 15

polynucleotide chains.

Question 16

Explain the specific bonding in nucleosides/nucleotides

Answer 16

1. The pentose sugar is always bonded to the base via carbon one.
2. This is then attached to N1 of pyrimidine bases or N9 on purine bases
3. Phosphate is always bonded to C5 of pentose sugar

Question 17

A nucleotide can also be called a

Answer 17

nucleoside mono-phosphate

Question 18

Question 19

What form of nucleotides act as precursors for nucleic acid synthesis ?

Answer 19

NTP - deoxynucleoside triphosphate

Question 20

ATP and GTP

Answer 20

Deoxyadenosine triphosphate

Deoxyguanine triphosphate

Question 21

why do ATP and GTP provide energy to the cell?

Answer 21

Due to the large amounts of energy involved in adding or removing the terminal phosphate from the molecule

Question 22

2 adjacent nucleotides are joined by a phosphodiester bond which is formed by:

Answer 22

The phosphoric acid moiety joining to 2 alcohols

- namely the 2 hydroxyl groups which were formally attached at positions C5 and C3 of the adjacent sugars

Question 23

what direction is a phosphodiester bond

Answer 23

3’ to 5’ phosphodiester bond

Question 24

Base composition studies performed by

Answer 24

Chargaff

Question 25

Base composition studies showed:

Answer 25

that DNA contained equal amounts of adenine and thymine molecules, while the amounts of cytosine and guanine correlated.
Additionally, the sum of the purines (A + G) are equal to the sum of the pyrimidines (C + T).
In contrast, the ratio (A + T)/(C + G) does not necessarily equal one.

This is is because A binds only to T and C binds only to G

Question 26

The final solution to understanding the DNA structure (double helix) was provided by X-ray diffraction…

Answer 26

Rosland franklin

Question 27

How does RNA structure differ from DNA?

Answer 27

Ribose instead of deoxyribose
Uracil instead of thymine
Single stranded, linear molecule
Three types of RNA - with different functions

Question 28

Three types of RNA

Answer 28

ribosomal RNA (rRNA), 
messenger RNA (mRNA) 
transfer RNA (tRNA)