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NUT1004 > DNA structure and function > Flashcards

DNA structure and function Flashcards

1
Q

What is the Central Dogma of Biology

A

The two step process of transcription and translation where genetic information flows from DNA to a protein

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2
Q

What is the genome

A

The complete set of DNA in an organism

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3
Q

What is the DNA replication error rate

A

1 error per 10 to the power of 10 per division

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4
Q

Are nitrogenous bases hydrophobic or hydrophilic

A

Hydrophobic

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5
Q

What are the purines

A

Guanine and Adenine

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6
Q

What are the pyrimidines

A

Cytosine, thymine and uracil

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7
Q

How many rings do purines and pyrimidines have

A

Purines have 2, pyrimidines have 1

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8
Q

What is the difference between a ribose and deoxyribose sugar

A

Ribose has a hydroxyl group (OH) bonded to carbon 2’ while deoxyribose has no oxygen bound to carbon 2’ (H)

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9
Q

What type of bonds are phosphodiester bonds

A

Covalent

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10
Q

Where do covalent bonds form

A

Between atoms that share electrons (very strong bonds)

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11
Q

Where do phosphodiester bonds form between nucleotides

A

Between the 5’ carbon of one nucleotide and the 3’ carbon of the next nucleotide

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12
Q

What is the difference between nucleotides and nucleosides

A

Nucleosides are only the base and sugar, nucleotides are the base, sugar and phosphate

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13
Q

Where do hydrogen bonds form in DNA

A

Between nitrogenous bases due to an electrostatic attraction between a proton in one and an electronegative atom in the other

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14
Q

What is Chargaff’s rule

A

There is always an equal amount of A and T and C and G in DNA and the total of purines and pyrimidines is always equal

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15
Q

How many hydrogen bonds form between A and T

A

2

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16
Q

How many hydrogen bonds form between C and G

A

3

17
Q

Which complementary base pairs require more energy to separate and why

A

C-G as they have more hydrogen bonds between them

18
Q

Why are DNA strands antiparallel

A

Bases can only fit together in a specific orientation so the sugar phosphate backbone must be in opposite directions

19
Q

What direction does the sense strand (forward) run in

A

From 5’ to 3’, left to right

20
Q

What direction does the antisense (reverse) strand run in

A

5’ to 3’, right to left

21
Q

What direction are DNA sequences always written in

A

5’ to 3’

22
Q

What are the grooves in DNA

A

The major groove and minor groove are sections of DNA where base pairs are exposed and can be accessed and interact with other molecules

23
Q

Why are the bases inside the DNA structure

A

They are hydrophobic

24
Q

Why is the sugar phosphate backbone outside the DNA structure

A

As the negativity charged phosphate interacts with cations (positively charged ions) and cationic proteins to reduce electrostatic repulsion of the phosphate groups

25
Q

What are the advantages of the DNA structure

A
  • extremely stable backbone due to negatively charged phosphates on the outsides
  • thermodynamically more stable than separated strands
26
Q

What is the chromatin structure

A

The packaging of DNA with proteins

27
Q

How is DNA packaged

A

By association with histones and non-histone proteins

28
Q

What is heterochromatin

A

Densely packaged chromatin, inactive as less accessible for transcription, darker region when stained

29
Q

What is euchromatin

A

Less densely packed region of chromatin, active region for gene expression as more accessible for transcription

30
Q

What is the order of packaging in chromatin

A

DNA, nucleosomes, solenoid fibre( chromatin fibre), scaffold loop( section of chromosome ), chromatid, chromosome

31
Q

What are nucleosomes

A

Fundamental repeating subunits of eukaryotic chromatin, where DNA is wrapped around a octamer (made of 8 histones)

32
Q

What are the roles of histone proteins

A
  • Packaging of DNA molecules so DNA is compact (structural)
  • regulatory mechanisms as reduce gene expression as DNA becomes more compact, (functional)
  • interact with negative charge of phosphate in DNA as histones are positively charged
  • dynamic so enable interactions with other proteins
33
Q

What are the roles of non-histone proteins in chromatin

A
  • functional role of regulating gene expression and stimulating genetic activity in transcription
  • negatively charged so interact with positively charged histones to reduce DNA-histone interactions or directly interact with DNA sequences
34
Q

In a sample of DNA if 30% is thymine, what are the percentages of other bases

A

A- 30%
G- 20%
C-20%

NUT1004 (14 decks)

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