Lecture 13 RNA Biology

Question 1

Compare the relative stabilities of RNA and DNA

Answer 1

• DNA is more stable

- RNA is more unstable

Question 2

Why is RNA less stable than DNA

Answer 2

The ribose sugar in ribonucleic acid has an added hydroxl group
- The presence of this hydroxyl group makes the RNA more likely to undergo change and thus more labile.

Question 3

Why is RNA suitable for more short term functions as opposed to an ideal storage molecule (like DNA)

Answer 3

as RNA is less stable than DNA and more likely to undergo change.

Question 4

In a cell, would you find more DNA or more RNA

Answer 4

In a cell there is 10 x more RNA than DNA!

Question 5

Describe the chemical structure of RNA.

Answer 5

• Ribose sugar
• ## Ribose sugar contains two hydroxyl groups

Question 6

Describe the chemical structure of DNA

Answer 6

• The ribose (pentose) sugar in DNA lacks an oxygen, and thus lacks the 2nd hydoxyl group.
• DNA has a hydrodgen instead.
• This makes DNA more stable

Question 7

Which bases are pyrimidine

Answer 7

Adenine and Guanine.

Question 8

Which bases are purine bases

Answer 8

Cytosine and Thymine

Question 9

4 bases in RNA are…

Answer 9

Adenine, Guanine, Cytosine and Uracil

Question 10

How does Uracil differ chemically from Thymine

Answer 10

• Thymine has a methyl group as its R group
• Uracil lacks this methyl R group
• Uracil has a hydrogen as its R group

Question 11

The R group in the Uracil base is what….

Answer 11

A hydrogen

Question 12

The R group in the Thymine base is…

Answer 12

A methyl group

Question 13

Describe the two key functions of small nuclear RNA

Answer 13

• Small nuclear RNA catalyzes the removal of introns from pre MRNA.
• Small nuclear RNA processes and modifies ribosomal RNA.

Question 14

What are two features of catalytic RNA

Answer 14

• It has self splicing introns

- it has natural and artificial created ribozymes ??

Question 15

Roughly how much RNA is present within a single cell

Answer 15

10pg
This is equal to 10^-11 grams of RNA.
This is 10 x more than the amount of cellular DNA.

Question 16

Describe the relative compositions of the different types of RNA present in a cell

Answer 16

• 85 percent of total RNA is ribosomal RNA
• 10-15 percent is transfer RNA and small nuclear RNA (these are low molecular weight RNA’s)
• 1-5 percent of total RNA is messenger RNA.

Question 17

Which type of RNA comprises the greatest proportion of total cellular RNA

Answer 17

Ribosomal RNA constitutes 85 percent of total RNA in the cell

Question 18

Describe the physical features of RNA

Answer 18

• Single stranded polynucleotide chains typically
• tends to fold back on itself and complementary base pair with itself forming hair pin loop structures
• tend to bury themselves on the inside of water molecules,

Question 19

Why does RNA tend to fold back on itself

Answer 19

There is an entropy price to pay, due to an exposed end.

Question 20

Which type of nucleotide sequences are capable of forming a hair pin

Answer 20

Palindromic sequences

Question 21

List reasons why secondary structure of RNA is important

Answer 21

• Catalysis
• Organization
• Recognition

Question 22

State the ways in which the amount of RNA can be regulated within the cell

Answer 22

• synthesis
• Degradation of RNA via the transferrin receptor
• Proteins can control the use of certain RNA’s, eg the ferritin messenger RNA.