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FSCI6370 - DNA > DNA Structure > Flashcards

DNA Structure Flashcards

1
Q

What is the central dogma of biology?

A
  • it deals with the detailed residue-by-residue transfer of sequential information
  • it states that such information cannot be transferred back from protein to either protein or nucleic acid
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2
Q

Draw out the DNA to RNA to protein flow chart?

A

DNA - DNA - replication
DNA - RNA - transcription
RNA - DNA - reverse transcription
RNA - RNA - replication
RNA - protein - translation

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3
Q

What are the three components of nucleic acids/DNA?

A
  • base pairs
  • phosphodiester / Phosphate Group
  • (deoxy)ribose / Sugar
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4
Q

What is DNA?

A

DNA is a polymer composed of two polynucleotide chains that coil around each other

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5
Q

What are the two forms of nucleobases?

A
  • pyrimidine
  • purine
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6
Q

What are the five base pairs?

Which ones are based from pyrimidines and which ones are based from purines?

A

pyrimidine:
- cytosine
- uracil
- thymine

purine:
- adenine
- guanine

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7
Q

Which base pairs pair up?

How many hydrogen bonds between each?

A

AT - adenine and thymine
- 2 hydrogen bonds DA/AD

CG - cytosine and guanine
- 3 hydrogen bonds ADD/DAA

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8
Q

What is ribose?

A
  • a sugar and has standard structure of sugar
  • it goes between planar and cyclic structure - there is an equilibrium which exists between the two
  • it is metabolically produced from glucose (reduction of glucose)
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9
Q

How is deoxyribose produced?

A
  • it is generated from ribose 5-phosphate by enzymes called ribonucleotide reductases which catalyse the deoxygenation process
  • nucleobase replaces the OH on the RHS
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10
Q

What is the main link between two nucleotides?

A
  • phosphodiester links 5’ to 3’
  • this asymmetric linkage gives DNA strands direction (gives it curved structure)
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11
Q

Define nucleobases, nucleoside and nucleotide?

A
  • nucleobase = base pairs
  • nucleoside = base pair + sugar
  • nucleotide = base pair + sugar + phosphate
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12
Q

What are the five nucleosides called and therefore what are the five nucleotides?

A
  • adenosine
  • cytidine
  • guanosine
  • thymidine
  • uridine
  • adenosine 5’-phosphate
  • cytidine 5’-phosphate
  • guanosine 5’-phosphate
  • thymidine 5’-phosphate
  • uridine 5’-phosphate
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13
Q

What is the antiparallel duplex?

A
  • one side of the DNA strand going from 5’-3’ down and the other side 5’-3’ up
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14
Q

What is the primary structure of DNA?

A
  • sequence of nucleotides
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15
Q

How is DNA duplex formed?

A
  • with strand of complementary sequence (complementary bases in opposite order)
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16
Q

What can be said about link between stability and G-C contetnt?

A
  • longer duplex with higher G-C content = more stable
  • more hydrogen bonds so more stable
17
Q

How do you find complementary sequence?

A
  • split strand into three base pairs
  • write down complementary bases
  • reverse the order to give strand in 5’ to 3’ format?
18
Q

What are main features of DNA double helix? (handed, turn, width, nucleotides per turn, grooves, base stacking distance)

A
  • right handed
  • 1 turn = 33A
  • width = 20A
  • 10.5 nucleotides per turn
  • major and minor groove
  • base stacking distance = 3.3A
19
Q

Why is DNA in a double helix?

A
  • negatively charged phosphate groups repel each other so when they are separated there is a reduced electrostatic repulsion
  • stacking of nucleobases through hydrophobic/van der Waals interactions compact duplex vertically - removal of water (as water would disrupt hydrogen bonding if bases closely packed) causing hydrophobic collapse and pi stacking
  • base pairs hydrogen bond
20
Q

What are three forms of double helix forms?

When do these usually occur

A
  • A-DNA - right handed - occurs under dehydrated conditions or in hybrid DNA-RNA
  • B-DNA (most common) - right-handed - found in cells under physiological conditions
  • Z-DNA - left-handed - after DNA has undergone methylation - common in some diseases (Alzheimer’s)
21
Q

What is triplex DNA?

A
  • where 3rd strand binds in major groove
22
Q

What is quadruplex DNA?

A
  • 4 strands of DNA around a metal ion
  • G-Quadruplex found in telomeres (end of chromosomes)
  • protects DNA ends and stop DNA repair systems from treating them as damaged
  • allows copying of ends which wouldn’t be possible with 3’ end
23
Q

What are some examples of tertiary structures of DNA?

A
  • hairpin (small loop)
  • stem-loop (large loop)
  • Holliday junction
24
Q

What are some differences between DNA and RNA structures? (sugar, base paid, single or double stranded, use, location)

A
  • DNA contains 2-deoxyribose
  • RNA contains ribose
  • DNA uses thymine
  • RNA uses uracil
  • DNA is usually double stranded
  • RNA is usually single stranded
  • DNA - stores genetic information
  • RNA - protein synthesis and gene regulation
  • DNA located in nucleus
  • RNA located in cytoplasm
25
Q

Why is ribose more easily hydrolysed than 2-deoxyribose

A
  • further possible hydrogen bonds patterns from extra OH so phosphodiester more easily hydrolysed
26
Q

What are some RNA structures?

A
  • hairpin
  • bulge
  • stem-loop
  • bubble/interior loop
27
Q

What is a nucleosome?

A
  • DNA coiled around proteins called histones to produce nucleosomes
  • 8 protein units required for each nucleosome
28
Q

What is a chromosome?

A
  • DNA coiled around proteins called histones to produce nucleosomes which are further packed to produce chromosomes
29
Q

How is nanotechnology used with DNA?

A
  • predictable sequence-specific hybridisation can be used to create 3D nanostructures for a wide variety of nanotechnological applications
30
Q

What are the functions of DNA?

A
  • DNA directs machinery of a cell to make specific proteins
  • stores the hereditary information of an individual
  • has the ability to mutate - allows for new characteristics (evolution)

FSCI6370 - DNA (16 decks)

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