Nucleic Acids, Structure, Chemistry and DNA Sequences

Question 1

What is the direction of DNA and RNA?

Answer 1

5’ to 3’

Question 2

What are the TWO Purines?

Answer 2

1. Adenine
2. Guanine

Question 3

What are the THREE Pyrimidines?

Answer 3

1. Cytosine
2. Thymine (DNA)
3. Uracil (RNA)

Question 4

What is the structure of DNA?

Answer 4

• Nitrogenous base
• Phosphate
• Pentose sugar (deoxyribose)

Question 5

What is the structure of RNA?

Answer 5

• Nitrogenous base
• Phosphate
• Pentose sugar (ribose)

Question 6

What is the difference in structure of a Ribonucleotide and a Deoxyribonucleotide?

Answer 6

• Ribonucleotide has OH at 2’C
• Deoxyribonucleotide has H at 2’C

Question 7

What bonds link nucleotides?

Answer 7

Phosphodiester
* 5’ OH of one ribose is linked to the 3’ OH of the next ribose

Covalent backbone

Question 8

How many bonds does A-T have?

Answer 8

2

Question 9

How many bonds does G-C have?

Answer 9

3

Question 10

What is the structure of DNA?

Answer 10

Right handed double helix
* Complementary strands
* Anti-parallel
* Flexible

Question 11

What happens in DNA during deamination (loss of amino groups)?

Answer 11

Cytosine changed to Uracil

Question 12

How does loss of purines happen?

Answer 12

Due to hydrolysis of bond between base and pentose AP or apurinic site

Question 13

What does radiation damage do to nucleotides and nucleic acids?

Answer 13

• UV light: Cyclobutane pyrimidine dimers
• Ionising radiation: Ring opening, breaks in backbone

Question 14

What are some chemicals that cause mutations in nucleotides and nucleic acids?

Answer 14

• Deminating agents
• Alkylating agents

Question 15

What are some examples of oxidative damage to nucleotides and nucleic acids?

Answer 15

• Hydrogen peroxide
• Hydrogen radicals

Question 16

Where do Hairpin Loop structures occur?

Answer 16

In single DNA strand or RNA

Question 17

Where do Cruciform structures occur?

Answer 17

Double strands

Question 18

Why is DNA and RNA secondary structure important for function?

Answer 18

1. Sites for binding of regulatory proteins
2. Catalytic activity: removal of introns from DNA
3. Transfer RNA: an adapter molecule in protein synthesis

Question 19

What does the melting point of DNA depend on?

Answer 19

• pH
• Ionic strength
• Size
• Base composition

Question 20

What is HOMODUPLEX DNA?

Answer 20

Both strands are from the same species

Question 21

What is HETERODUPLEX DNA?

Answer 21

Strands from different species with some bases unpaired

Question 22

What is the technique for detecting identical or similar DNA from different species called?

Answer 22

Hybridisation

Question 23

What are some applications of Near-Complimentary Hybrids in DNA and RNA?

Answer 23

• Detection of a specific DNA molecule in complex mixture
• Amplification of specific DNA fragments
• Evolutionary relationships
• Antisense oligonucleotides

Question 24

What are Genes?

Answer 24

Segments of DNA that code for polypeptides and RNAs

Question 25

What is Sanger Sequencing?

Answer 25

• DNA polymerase used to introduce a labelled nucleotide complimentary to nucleotide in template DNA strand
• Introduces ddNTP analogs to interupt DNA synthesis
• Fragments then separated and nucleotide sequence is then read

Question 26

How many base pair fragments is “Next Gen” sequencing now able to sequence?

Answer 26

400-550