DNA and RNA

Question 1

What are the Purines

Answer 1

Adenine and Guanine
2 Rings

Pur Ag Rings

Question 2

What are the pyrimidines?

Answer 2

Cytosine, Uracil, Thymine

1 Ring

CUT py pie is a ring

Question 3

Nucleotide vs Nucleoside

Answer 3

Nucleotide has a phosphate on the 5’ OH of the Sugar

Nucleoside is a Sugar and N-Base only

Question 4

What is the five carbon ring of RNA and DNA called?

Answer 4

Furanose ring

Question 5

What is the difference between the furanose ring of RNA vs DNA?

Answer 5

The furanose ring of RNA has an OH on the 2’ Carbon. In DNA there is an H at the 2’ Carbon

Question 6

What pairs together with DNA?

Answer 6

Purine always pairs with a pyrimidine

A-T
A-U
G-C

Question 7

How many bonds form between the bases of A-T, A-U, G-C?

Answer 7

A-T, A-U = 2 hydrogen bonds

G-C = 3 hydrogen bonds

Question 8

How are DNA monomers linked?

Answer 8

They are linked by phosphodiester bonds of the 3’ and 5’ carbons of the furanose rings. By convention, they are usually written in a 5’ to 3’ direction.

Question 9

What increases the Melting Point of DNA?

Answer 9

The more G-C bonds there are, the higher the MP due to more hydrogen bonds. 3 hydrogen bonds vs 2 with A-T

Question 10

As DNA length increases what happens to the Melting Point

Answer 10

The melting point also increases due to more hydrogen bonds between N-Bases

Question 11

As NaCl concentration increases what happens to the melting point of DNA?

Answer 11

DNA melting point increases.

DNA is highly negatively charged and the phosphodiester linkages normally repel each other, weakening the interaction between the strands. NA+ will actually for cation shields around the linkages that then strengthen the bonds of the helix.

Question 12

What happens to renaturation of single strands to double strands as DNA concentration of single strands increases?

Answer 12

The renaturation of single strands to double strands increase as well.

Like any chemical reaction, the molecules need to be oriented in the right direction for an interaction to occur. When you increase the concentration of reactans, in this case DNA, you also increase the likelihood that the reactants will meet in the proper orientation. The rate therefore increases.

Question 13

What happens to the Tm (melting point) of DNA as Urea is added to the solution?

Answer 13

Melting point decreases as Urea is added to the solution.

Urea is a polar molecule that is capable of being a hydrogen bond donor and acceptor:

H2N-CO-NH2

This disrupts the hydrogen bonds of DNA and weakens the double helix.

Question 14

If DNA has 20% cytosine, what percentage of Adenine does it have?

Answer 14

It will have 30% adenine.

20% cytosine means 20% guanine, leaving 60% for adenine and thymine combined.

Question 15

What is the water solubility of the phosphate groups, the ribosyl group, and the nitrogen bases?

Answer 15

Phosphate is negatively charged, so it will be hydrophilic. The hydrogen dipoles will surround the charged parts of the phosphate group

The Ribosyl group is polar with it’s oxygen right before the 1’ Carbon. It will be hydrophilic as well.

The N base is mostly hydrophobic so it groups to the middle.

Question 16

What biology or histology technique is used to identify chromosomal material or DNA?

Answer 16

We use the Feulgen stain. DNA stains reddish in color. Mild acid hydrolysis cleaves the molecule and a reaction reveals the red color.

Question 17

What is a nucleosome

Answer 17

DNA wrapped around histones make up the nucleosome

This is the basic unit of DNA packaging

Question 18

What unique characteristic of histones helps with DNA binding?

Answer 18

Histones are rich in the positively charged amino acids lysine and arginine. These amino acids are able to bind tightly to the negatively charged phosphate groups of DNA.

Question 19

What is Euchromatin?

Answer 19

Euchromatin is the DNA that is actively transcribing. It is used to form YOU.

True chromatin

It stains lightly and is more dispersed and less compact

Question 20

What is Heterochromatin

Answer 20

Heterochromatin is wound up tightly and is not actively transcribing.

It is located mostly near the nuclear envelope

It stains dark in electron micrographs

Question 21

Hershey-Chase experiment

Answer 21

Concluded that DNA and not protein is the actual genetic information

They used radioactive phosphorous and sulfur on bacteriophages to see whether protein (radioactive sulfur) or DNA (radioactive phosphorous) entered the bacterial cell. They found that it was the DNA.

Question 22

Fred - Griffith Transformation Experiment

Answer 22

Dr. Griffith had two strains of bacteria.

A. Pathogenic (disease causing)
B. Nonpathogenic

When he killed A with heat and mixed the cell remains with living B, nonpathogenic bacteria, some of the harmless B strain became pathogenic. All further progeny were also pathogenic.

This showed that something from the pathogenic bacteria had been passed to the other bacteria giving them those traits. That something, DNA

Question 23

Avery - McCarty - Macleod experiment

Answer 23

They took the griffith experiment further by systematically adding lipases, proteases, and ribonucleases (breaks down RNA) to be left with DNA that would be passed on to the bacteria to make it pathogenic.

Question 24

What are things that can damage DNA?

Answer 24

Radiation can damage DNA by modifying bases, cleaving strands, and other structural damage.

Free radicals can also damage DNA

Question 25

What are the three major kinds of RNA?

Answer 25

Ribosomal RNA (rRNA): provides physical makeup of the ribosome

Messenger RNA (mRNA): carries DNA information to the ribosomes.

Transfer RNA (tRNA): transports amino acids to ribosomes

Question 26

Is DNA or RNA more abundant in the cell?

Answer 26

RNA is 8x more abundant than DNA

Question 27

Ribosomal RNA

Answer 27

RNA used in the structure of the Ribosome.

The Ribosome is 60% RNA and 40% protein

This is the most abundant RNA

Question 28

Transfer RNA

Answer 28

Transports amino acids to ribosomes.

This is the smallest RNA with the lowest molecule weight

Question 29

Messenger RNA

Answer 29

This carries DNA information to the Ribosomes in a process called transcription

It is short lived

Question 30

Why do alkaline conditions partially denature (unwind DNA in certain areas) the helix?

Answer 30

Alkaline conditions promote ionization of the nitrogenous bases and phosphate groups, increasing the amount of negatively charged ions. This results in more negative repulsion and thus unwinds the helix.

A-T regions would unwind more readily than areas rich in G-C bonds

Question 31

Which would be more sensitive to a base? DNA or RNA?

Answer 31

RNA is more sensitive to a base.

The exposed 2’ OH on the ribose (absent from DNA) can be attacked by an OH- group. This attack pulls an H from the group causing the O to bond with the phosphate group. This causes the Phosphate group to lose the O on the phosphodiester bond at the 5’ carbon, thus cleaving the RNA molecule, leaving a nucleoside and a strange nucleotide with phosphate bound to the 2’ and 3’ oxygens.