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My Packs: (UWO) (BIOCHEM 2280) > (Dr. Heinemann) (Unit C) Topic 14 > Flashcards

(Dr. Heinemann) (Unit C) Topic 14 Flashcards

1
Q

Purines

A
  • 2 rings
  • Adenine (A) and Guanine (G)
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2
Q

Pyrimidines

A
  • 1 ring
  • Cytosine (C), Thymine (T), Uracil (U)
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3
Q

What are purines and pyrimidines?

A

Nitrogenous bases

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4
Q

What are the two major categories of nitrogenous bases?

A
  1. Purines
  2. Pyrimidines
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5
Q

What shapes are nitrogenous bases?

A
  • Flat
  • Hydrogen bonding groups on the outside
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6
Q

What types of bonds links nitrogenous bases together?

A

N-Glycosidic Bonds

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7
Q

2 major types of nucleic acids in humans

A
  1. Ribonucleic
  2. Deoxyribonucleic
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8
Q

Function:

DNA

A
  • Holds genetic material
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9
Q

Function:

RNA

A
  • Template from which proteins are produced (mRNA)
  • Ribosome formation (rRNA)
  • Catalyzing protein synthesis (rRNA)
  • Carrying amino acids to growing peptide chain (tRNA)
  • Gene regulation
  • mRNA splicing
  • Telomere maintenance
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10
Q

What are ribonucleotide/deoxyribonucleotide monomers comprised of?

A
  • A monosaccharide
  • A nitrogenous base
  • A phosphate
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11
Q

What is the difference between Uracil and Thymine?

A

Uracil lacks a methyl group

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12
Q

Where are purines/pyrimidines joined to monosaccharides?

A

Joined to the anomeric (1’) carbon of ribose/deoxyribose
* Via N-Glycosidic Bond

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13
Q

Nucleoside

A

Nitrogenous base joined to a sugar

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14
Q

List:

The 5 common nucleosides

A
  • Adenosine
  • Guanosine
  • Cytidine
  • Thymidine
  • Uridine
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15
Q

Where do phosphates attach to on a nitrogenous base?

A

Attached to the 5’ position of ribose/deoxyribose

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16
Q

What is the bond between phosphate and nitrogenous bases known as?

A

Phosphoester linkage

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17
Q

Nucleotide

A

Has 3 groups:
* A nitrogenous base
* A sugar
* A phosphate group

18
Q

What is the notation of nucleotides?

A
  1. Nitrogenous base
  2. Number of phosphates

E.x. ADP (Adenosine Diphosphate)

  • Sometimes deoxyribonucleotides will begin with a “d” (e.x. dTTP)
19
Q

Polynucleotide structure

A

Phosphate group at 5’ carbon on one pentose, forms phosphoester bond with hydroxyl group at the 3’ position of another pentose

20
Q

How are 5’ and 3’ ends determined in a polynucleotide?

A
  • 5’ free carbon (not attached to anything) is 5’ end
  • 3’ free carbon (not attached to anything) is 3’ end
21
Q

How are polynucleotides conventionally written?

A

5’ to 3’

22
Q

Oligonucleotides

A

“Short” (up to 200 base pairs)

23
Q

True or False:

Double helices are usually right handed

A

True

24
Q

What types of interactions between bases stabilize the double helix?

A
  1. Base stacking
  2. Base pairing
25
Q

Base stacking

A

As bases are planar aromatic rings, they can stack on top of each other and tstasbilize via interactions (London forces)

26
Q

Base pairing

A

Hydrogen bonding between chemical groups on edges of ring structure

27
Q

What are the different types of base pairings?

A
  • C and G: 3 bonds
  • A and T: 2 bonds
28
Q

What form of double helices do DNA usually form?

A

B-DNA double helix

29
Q

What are certain features of B-DNA double helices?

A
  1. Narrow (2 nm or 20 angstroms wide)
  2. Long (1 human chromosome is 245 million base pairs)
  3. Distance between consecutive bases is around 0.34 nm
30
Q

What are the two grooves in the sugarphosphate backbones known as?

A
  • Major groove
  • Minor groove
31
Q

Major groove

A

The wider groove in B-DNA double helices

32
Q

Minor groove

A

The narrower groove in B-DNA double helices

33
Q

5 differences between RNA and DNA

A
  1. Ribose vs. Deoxyribose
  2. Uracil vs. Thymine
  3. Shorter (few thousand nucleotides, usually)
  4. Single stranded (folds into cocmplex 3D structures
  5. More likely to chemically modify nitrogenous bases
34
Q

What can modified bases in RNA do?

A

Influence the secondary and tertiary structure of RNA

35
Q

Tm

A

The melting temperature
* Temperature at which 50% of a specific dsDNA has become single stranded

36
Q

What types of factors determines the Tm?

A
  • Intrinsic factors
  • Extrinsic factors
37
Q

Intrinsic factors that affect Tm

A
  1. A:T / G:C ratio: More GC content, the higher Tm
  2. Length: Longer means higher Tm
  3. Degree of complementarity: Imperfect matches have lower Tm
38
Q

Extrinsic factors that affect Tm

A
  1. Salt concentration: Increasing salt concentration increases Tm
  2. Organic solent concentration: Lowers Tm (reduces base stacking interactions)
  3. Hydrogen bonding compounds: Urea decreases Tm
  4. pH: Extreme pH decreases the Tm

(these do not need to be memorized, except for pH)

39
Q

How is melting temperature approximated?

A
  • 2 degrees Celsius for every AT
  • 4 degrees Celsius for every GC
40
Q

Chromatin

A

Organizes and packages DNA

41
Q

Histones structure

A
  • Fewer than 200 amino acids
  • Many lysine and arginine residues
42
Q

Nucleosome core particle

A

Wrapped DNA and histone core proteins

My Packs: (UWO) (BIOCHEM 2280) (23 decks)

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