BM: DNA & RNA

Question 1

Name two types of nucleic acid:

Answer 1

DNA and RNA

Question 2

What does DNA stand for?

Answer 2

Deoxyribonucleic acid

Question 3

What does RNA stand for?

Answer 3

Ribonucleic acid

Question 4

What is the function of DNA?

Answer 4

To store genetic information.

Question 5

What is the main function of RNA?

Answer 5

Transfers genetic information from DNA to the ribosomes.

Question 6

What do ribosomes do with the genetic information they receive from RNA?

Answer 6

They read the RNA to make polypeptides/proteins in a process called translation.

Question 7

What are ribosomes made of?

Answer 7

RNA and proteins

Question 8

What monomer makes up DNA and RNA?

Answer 8

Nucleotides

Question 9

What are nucleotides?

Answer 9

A type of biological molecule that is the monomer of nucleic acids.

Question 10

Draw a nucleotide and list its components:

Answer 10

• A pentose sugar
• A nitrogen-containing organic base
• A phosphate group

Question 11

What is a pentose sugar?

Answer 11

A sugar that contains 5 carbon atoms.

Question 12

How do they parts of a nucleotide join together?

Answer 12

Through condensation reactions to form a mononucleotide.

Question 13

How do two nucleotides join together?

Answer 13

Through a condensation reaction between the pentose sugar of one nucleotide and the phosphate group of another nucleotide.

Question 14

What bond forms between two nucleotides?

Answer 14

Phosphodiester bond.

(The bond is classed as the entirety of the phosphate group, and the two ester bonds on either side, joining the phosphate to the two pentose sugars).

Question 15

What is the pentose sugar in DNA?

Answer 15

Deoxyribose

Question 16

What are the four possible bases in DNA?

Answer 16

• Adenine
• Thymine
• Cytosine
• Guanine

Question 17

What pentose sugar does RNA have?

Answer 17

Ribose

Question 18

What are the four possible bases in RNA?

Answer 18

• Adenine
• Uracil
• Cytosine
• Guanine

Question 19

The chain of sugar and phosphates formed as a result of condensation reactions between nucleotides, is known as what?

Answer 19

Sugar-phosphate backbone.

Question 20

What structure does DNA have?

Answer 20

Double-helix

Question 21

What is a DNA molecule?

Answer 21

A double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.

Question 22

What is an RNA molecule?

Answer 22

A relatively short polynucleotide chain.

Question 23

How is the double-helix structure of DNA formed?

Answer 23

• Two DNA polynucleotide strands join together by hydrogen bonding between the bases - via complementary base pairing.
• The two antiparallel polynucleotide strands twist to form the double-helix.

Question 24

What is complementary base pairing?

Answer 24

Where bases only pair with one other type of base.

A & T (U)

G & C

Question 25

What does complementary base pairing mean for the amount of each base in a DNA molecule?

Answer 25

There will always be equal amounts of adenine and thymine and equal amounts of cytosine and guanine.

Question 26

How many hydrogen bonds form between adenine and thymine?

Answer 26

Two

Question 27

How many hydrogen bonds form between cytosine and guanine?

Answer 27

Three

Question 28

When was DNA first observed? ## Footnote *What did scientists first believe about it?*

Answer 28

The 1800s. ## Footnote *Scientists doubted it could carry genetic code because it has a relatively simple chemical composition. Some thought genetic info must be carried by proteins which are much more chemically varied.*

Question 29

When was it shown that DNA carried the genetic code? ## Footnote *What was also discovered at this time?*

Answer 29

1953. ## Footnote *Also the year that **Watson and Crick** determined the double-helix structure, which helps DNA to carry out its function.*

Question 30

Why is DNA a stable molecule?

Answer 30

* Phosphodiester backbone protects the more chemically reactive bases within the double helix. * Hydrogen bonds linking bases form bridges between backbones, offering stability - higher proportion of C & G pairings, the more stable the molecule (as this pairing has higher amount of bonds).

Question 31

How is DNA adapted to carry out its function?

Answer 31

* Very stable structure which passes from generation to generation unchanged - mutations are repaired, so persistent mutations are uncommon. * Two strands are joined with weak hydrogen bonds allowing for easy separation during replication and protein synthesis. * Extremely large molecule, so carries lots of genetic information. * Base pairs are within the helical cylinder of deoxyribose-phosphate backbone, so genetic info is somewhat protected from being corrupted by chemical or physical forces. * Base pairing leads to DNA being able to replicate and to transfer information as mRNA.

Question 32

What are the similarities and differences between RNA and DNA?

Answer 32