2.1 Structure of RNA and DNA

Question 1

What are the 2 main types of nucleic acids?

Answer 1

1. DNA
2. RNA

Question 2

Both DNA and RNA are the polymer of ___ .

Answer 2

Nucleotides

Question 3

In other words, both DNA and RNA are ___ .

Answer 3

Polynucleotides

Question 4

What are made up of a nucleotide?

Answer 4

1. pentose sugar
2. phosphate
3. nitrogenous/nitrogen-containing base

Question 5

What are the 5 types of nitrogenous bases?

Answer 5

1. A - adenine
2. T - thymine
3. C - cytosine
4. G - guanine
5. U - uracil

Question 6

How are the pentose sugar, phosphate and organic base joined? What is formed?

Answer 6

By condensation. To form a single nucleotide.

Question 7

What is formed when two nucleotides are joined together by condensation?

Answer 7

Dinucleotide

Question 8

What is formed when many nucleotides are joined together by condensation?

Answer 8

Polynucleotide

Question 9

What bond is linked between two nucleotides?

Answer 9

Phosphodiester bond

Question 10

What is a DNA molecule?

Answer 10

A double helix with two polynucleotide chains

Question 11

What type of pentose sugar does a DNA nucleotide have?

Answer 11

Deoxyribose

Question 12

What are the 4 types of nitrogenous bases can a DNA nucleotide have?

Answer 12

1. A - adenine
2. T - thymine
3. C - cytosine
4. G - guanine

Question 13

What bond is linked between specific complementary nitrogenous base pairs?

Answer 13

Hydrogen bond

Question 14

How are the nitrogenous bases paired?

Answer 14

Adenine always pairs with thymine, guanine always pairs with cytosine.

Question 15

What are purines? Which 2 bases are purines?

Answer 15

Larger bases that contain two carbon ring structures. A and G are purines.

Question 16

What are pyrimidines? Which 2 bases are pyrimidines?

Answer 16

Smaller bases that contain one carbon ring structure. T and C are pyrimidines.

Question 17

How many hydrogen bonds are needed for adenine to pair with thymine?

Answer 17

2

Question 18

How many hydrogen bonds are needed for cytosine to pair with guanine?

Answer 18

3

Question 19

In what direction do the two strands of DNA run in?

Answer 19

Opposite direction/anti-parallel. One strand runs in the 5’ to 3’ direction and the other runs in the 3’ to 5’ direction.

Question 20

What is the function of DNA?

Answer 20

Holds genetic information

Question 21

Why is DNA a stable molecule?

Answer 21

1. the phosphodiester backbone protects the more chemically reactive nitrogenous bases inside the double helix
2. hydrogen bonds link nitrogenous base pairs forming bridges between phosphodiester uprights (立柱)
3. as there are 3 hydrogen bonds between cytosine and guanine, the higher the proportion of C-G pairings, the more stable the DNA molecule

Question 22

How is DNA adapted to carry out its function?

Answer 22

1. it is a stable molecule - so it is normally passed from generation to generation without significant change
2. its two separate strands are only bonded with hydrogen bonds - so it can be separated during DNA replication and protein synthesis
3. it is very large - so it carries a huge amount of genetic information
4. the bases are paired - so DNA can be replicated and tranfered as mRNA
5. the bases are within the helical cylinder of the deoxyribose-phosphate backbone - so the genetic information can be protected

Question 23

What is a RNA molecule?

Answer 23

A relatively short polynucleotide chain

Question 24

What type of pentose sugar does a RNA nucleotide have?

Answer 24

Ribose

Question 25

What are the 4 types of nitrogenous bases can a RNA nucleotide have?

Answer 25

1. A - adenine
2. C - cytosine
3. G - guanine
4. U - uracil

Question 26

What is the function of RNA?

Answer 26

Transfers genetic information from DNA to the ribosomes

Question 27

How are ribosomes formed?

Answer 27

From RNA and proteins