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BCM210 > Topic 7 - Nucleic Acids > Flashcards

Topic 7 - Nucleic Acids Flashcards

1
Q

List the functions of a nucleotide

A

Energy for metabolism (ATP) Enzyme cofactors (NAD+) Signal Transduction (cAMP)

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2
Q

List the functions of nucleic acid

A

Storage of genetic info (DNA) Transmission of genetic info (mRNA) Processing genetic info (ribozymes) Protein synthesis (tRNA & rRNA)

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3
Q

What is a gene?

A

segment of DNA that encodes a protein

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4
Q

Name the two types of nucleic acid

A

DNA (deoxyribonucleic acid) RNA (ribonucleic acid)

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5
Q

What is the function of DNA?

A

Storage and transmission of biological info

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6
Q

What is the function of mRNA?

A

Messenger RNA: intermediates, carry genetic info from genes to ribosomes

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7
Q

What is the function of tRNA?

A

Transfer RNA: adapter molecules, transfer specific aa’s to proteins at ribosomes

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8
Q

What is the function of rRNA?

A

Ribosomal RNA: protein synthesis

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9
Q

Name the 3 components of a nucleotide, and where some of these are attached

A

Nitrogenous base (N containing) attached at 1’

Pentose (5-membered sugar)

Phosphate attached at 5’

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10
Q

Describe the structural difference b/w DNA & RNA

A

If only H attached would be deoxyribose

If OH attached is ribose

Picture below shows a ribose

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11
Q

Phosphate group is negatively charged at a neutral pH, and are attached to the 5’ position.

T or F?

A

True

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12
Q

Name the nucleotides that make up DNA & RNA

A

Adenine triphosphate (ATP)

Guanine triphosphate (GTP)

**Thymine triphosphate (TTP)

Cytosine triphosphate (CTP)

**Uracil triphosphate (UTP)

**RNA does not have TTP. Has UTP instead, which binds w/ ATP.

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13
Q

Name the two types of pentose (5-membered sugar)

A

ribose (OH) group

deoxyribose (H) group

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14
Q

Name the two types of nitrogenous bases, what type of structure they are and their components

A

Purines (adenine & guanine) => lrg, bicyclic

Pyrimidines (cytosine, thymine & uracil) =>sml, monocyclic

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15
Q

Draw the basic structure of a purine

A
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16
Q

Draw the basic structure of a pyrimidine and give some info

A

All NH groups are attached to sugar

Amino group (HN) wants to give up its H

Carbonyl group (C=O) wants to H bond

17
Q

Just some general info to read on structure!

A
  • 5’-phosphate of one nucleotide is linked w/ 3’-hydroxyl group of next nucleotide
  • Back bone of nucleic acids consist of alternating phosphate & sugar
  • Bases are regarded as side groups, hydrophobic
  • Ribo-phosphate backbone is hydrophilic and -ve charged
18
Q

What direction are gene sequences written in?

A

5’ to 3’ direction

19
Q

If purine on one strand, other strand must have a pyrimidine & vice versa.

(view pic in answer)

A

broken line indicates H bonding

20
Q

Properties of nucleotide bases affect nucleic acid structure.
T or F?

A

True

21
Q

Describe Chargaff’s rule

A

ratio of pyrimidine to purine is 1:1

i.e. amount of guanine is equal to cytosine

amount of adenine is equal to thymine

22
Q

What is it about nitrogenous bases that allows them to absorb UV light?

A

aromatic nature (cyclic structure)

23
Q

Describe the structure of the double helix

A
  • two antiparallel complementary helical chains
  • hydrophilic backbone (sugar & phosphate) are on outside
  • purine and pyrimidine bases are stacked inside helix
  • Major & minor groove
  • Main forces that stabilise helix are: H bonding & base stacking
24
Q

DNA replication is semiconservative. Why?

A

Each DNA strand acts as a template for synthesis of a new strand

-progeny DNA consists of one parent and one newly synthesised strand

25
Q

Describe the basis of DNA replication

A

Always occurs in the 5’-3’ direction

  • one strand is complement of the other
  • separate two strands
  • synthesise completely new strand using existing strand as template
  • occurs are replication fork
  • leading and lagging strand
26
Q

Name the enzymes & their functions involved in DNA replication in E.Coli

A

DNA polymerase III => catalyses reaction, proof reading

DNA helicase => unwinds double stranded DNA to allow access by polymerase

**Topisomerases **=> relieve topological ‘super coal’ stress as helix is unwound

**Primase **=> synthesis short pieces of RNA to allow DNA Pol. to initiate replication

single stranded binding proteins (not enzymatic)

27
Q

Describe the central dogma of flow of info from DNA to translation

A

DNA=>(transcription)=>RNA=>(translation)=>PROTEIN

28
Q

describe process of DNA transcription and what it requires

A

very selective

RNA is synthesised by RNA polymerases, which require:

  • DNA template,
  • all 4 ribonucleotides (A,G,C,U)
  • Mg2+
  • Zn2+

Enzyme elongates RNA by adding ribonuc. to 3’ end

Each nucleotide inserted is selected by base pairing

  • Does not require a primer for initiation; init. occurs when RNA polymerase binds promotor region
  • DNA unwound to form bubble; involves only limited segments of DNA
  • RNA polymerase lacks proof reading ability
29
Q

3 nucleotides encode each aa. What are these 3 nucleotides called?

A

Codons

30
Q

Reading frames & genetic code

-see pic in answer

A
31
Q

Genetic code & degeneracy

-see pic in answer

A
32
Q

Genetic code and codon function

-see pic in answer

A

BCM210 (18 decks)

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