DLA #7: Structure and Function of Nucleic Acids

Question 1

DNA and RNA are considered

Answer 1

Nucleic Acids

Question 2

DNA/RNA are basically a series of ______ linked together by a ______

Answer 2

• Nucleotides
• Phosphodiester Bond

Question 3

A nucleotide is comprised of

Answer 3

• a phosphate
• a pentose sugar
• a nitogenous base

Question 4

Phosphates are linked at which carbon of the sugar base

Answer 4

The 5th carbon

Question 5

The phosphodiester bond links the ____ of one nucleotide to the____ of another

Answer 5

-5’ Phosphate to a 3’ OH

Question 6

Ribose is found in ______ and dRibose is found in ______

Answer 6

RNA, DNA

Question 7

What is the chemical difference b/w Ribose and dRibose

Answer 7

dRibose has a H at the 2’

Ribose has a OH at the 2’

Question 8

Name the two categories of nitrogenous bases

Answer 8

1) Purines
2) Pyrimidines

Question 9

Give a VERY general description of purine vs pyrimidines and list all that exist

Answer 9

Purines => Double ring structure

• ​Purine list is:
  
  • 1) Adenine
  • 2) Guanine
  • Mnemonic: “Pure As Gold

Pyrimidines => Single ring structure

• Pyrimidine list is:
  
  • ​1) Cytosine
  • 2) Thymine
  • 3) Uracil (only in RNA)
  • Mnemonic: “CUt The Pye”

Question 10

The nitrogenous base of a nucleotide is attached at which carbon of the pentose sugar

Answer 10

1’ Carbon

Question 11

Explain the big difference b/w DNA and RNA when it comes to nitrogenous bases

Answer 11

DNA:

A=T

RNA:

A=U

Question 12

The hydroxyl group of a nucleotide is found on the

Answer 12

3’ Carbon of the pentose sugar

Question 13

A nucleoside consists of

Answer 13

• A nitrogenous base
• A sugar group (Ribose/dRibose)

Question 14

Explain the difference b/w a nucleoside and a nucleotide

Answer 14

Nucleotide => Prescence of phosphate

Nucleoside => No phosphate

Question 15

Another way of expressing a nucleotide is by calling it

Answer 15

• Nucleoside monophosphate (1 Phosphate)
• Nucleoside diphosphate (2 Phosphate)
• Nucleoside triphosphate (3 Phosphate).

**** A NUCLEOTIDE = NUCLEOSIDE + PHOSPHATE.

**** Popular examples of nucleoside triphosphates include:

• ATP (Adenosine Triphosphate) => Energy
• GTP (Guanosine Triphosphate) => Protein synthesis
• UTP (Uridine Triphosphate) => carrier molecule

Question 16

Name two enzymes that can catalyse the formation of a phosphodiester bond b/w Nucleotides:

Answer 16

1) Polymerase (DNA/RNA)
2) Ligase (attaches the Okazaki together)

***Okazaki fragments are short segments of DNA

Question 17

DNA polymerase synthesizes the formation of phosphodiester bonds in what direction

Answer 17

5’ => 3’

Question 18

When nitogenous bases are being attaches together via a phospodiester linkage, what is the source of energy from this rxn

Answer 18

• Energy is from release of 2Pi (inorganic phosphate)
• Polymerase enzymes catalyzes the binding of nucleotides. Nucleoside triphosphates are brought in, 2 Pi leave, and we are left with a nucleoside mono phosphate.

Question 19

Topopisomerases/Gyrases have what two types of enzymatic activity

Answer 19

• Ligase activity (“Phosphodiester bond breaker”)
• Exonuclease activity (“Phosphodieser bond sealer”)

Question 20

What is the ratio of purines vs pyrimidines w/in the DNA:

Answer 20

50/50

Question 21

How are the two stands of DNA oriented.

Answer 21

Antiparallel

Question 22

What type of double helix does our DNA form

Answer 22

-right handed

Question 23

What type of bonding holds base bases together

Answer 23

-Hydrogen bonds

Question 24

Explain which nitrogenous bases bind to which. What are their relative strengths?

Answer 24

Question 25

What is the melting temperature (Tm) in regards to DNA

Answer 25

Temperature in which 50% of DNA becomes single stranded

Question 26

Describe re-annealing

Answer 26

Event in which seperated DNA stranded (seperated base pairs) reforms hydrogen bond.

Question 27

What is Chargaff’s Rule

Answer 27

• DNA from any cell of any organism should have a 1:1 stoichiometric ratio (base pair rule) of pyrimidine and purine bases
• means that amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.

Question 28

What is mRNA

Answer 28

• linear single stranded molecule
• carries codon information for translation
• post transcriptionally modified -
• 2% of total RNA

Question 29

what is tRNA

Answer 29

• folded stem loop structures formed by intramolecular H-bonding
• carries amino acid to ribosome
• 16% of total RNA

Question 30

What is rRNA

Answer 30

• linear single stranded, folded molecule
• complexes with protein to form ribosome
• rRNA => important for forming polypeptide bonds
• 82% of total RNA

Question 31

what is snRNA

Answer 31

• helps to mature pre-mRNA into mRNA.
• done via “splicing”

-Introns are removed (“introns in the trash”)

Question 32

What are introns and exons

Answer 32

• Introns => Non-proteins coding regions
• Exons => Protein coding regions
• We want exons to remain in the mRNA during splicing

Question 33

What are miRNAs

Answer 33

• miRNA regulate gene expression.
• Carry proteins complexes to the mRNA
• These proteins can inhibit translation in two different ways:
• 1) Block the ribosome form binding to mRNA
• 2) Degrade the mRNA