DNA and RNA Flashcards

1
Q

What are the Purines

A

Adenine and Guanine
2 Rings

Pur Ag Rings

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2
Q

What are the pyrimidines?

A

Cytosine, Uracil, Thymine

1 Ring

CUT py pie is a ring

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3
Q

Nucleotide vs Nucleoside

A

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

Nucleoside is a Sugar and N-Base only

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4
Q

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

A

Furanose ring

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5
Q

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

A

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

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6
Q

What pairs together with DNA?

A

Purine always pairs with a pyrimidine

A-T
A-U
G-C

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7
Q

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

A

A-T, A-U = 2 hydrogen bonds

G-C = 3 hydrogen bonds

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8
Q

How are DNA monomers linked?

A

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.

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9
Q

What increases the Melting Point of DNA?

A

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

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10
Q

As DNA length increases what happens to the Melting Point

A

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

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11
Q

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

A

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.

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12
Q

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

A

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.

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13
Q

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

A

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.

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14
Q

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

A

It will have 30% adenine.

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

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15
Q

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

A

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.

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16
Q

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

A

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

17
Q

What is a nucleosome

A

DNA wrapped around histones make up the nucleosome

This is the basic unit of DNA packaging

18
Q

What unique characteristic of histones helps with DNA binding?

A

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.

19
Q

What is Euchromatin?

A

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

20
Q

What is Heterochromatin

A

Heterochromatin is wound up tightly and is not actively transcribing.

It is located mostly near the nuclear envelope

It stains dark in electron micrographs

21
Q

Hershey-Chase experiment

A

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.

22
Q

Fred - Griffith Transformation Experiment

A

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

23
Q

Avery - McCarty - Macleod experiment

A

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.

24
Q

What are things that can damage DNA?

A

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

Free radicals can also damage DNA

25
Q

What are the three major kinds of RNA?

A

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

26
Q

Is DNA or RNA more abundant in the cell?

A

RNA is 8x more abundant than DNA

27
Q

Ribosomal RNA

A

RNA used in the structure of the Ribosome.

The Ribosome is 60% RNA and 40% protein

This is the most abundant RNA

28
Q

Transfer RNA

A

Transports amino acids to ribosomes.

This is the smallest RNA with the lowest molecule weight

29
Q

Messenger RNA

A

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

It is short lived

30
Q

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

A

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

31
Q

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

A

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.