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molecular genetic > DNA and RNA > Flashcards

DNA and RNA Flashcards

1
Q

DNA and RNA is made up of …

A

Base>Scaffold>connector

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2
Q

Differences between DNA and RNA is

A
  • 2-deoxyribose (H instead of OH in position 2) vs ribose
  • Thymine vs Uracil
  • double stranded vs single stranded
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3
Q

Nitrogenous bases bind to sugar at carbon position ____

A

1

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4
Q

AT bp has __ bonds and GC bp has __ bonds

A

AT bp has 2 bonds and GC bp has 3 bonds (stronger)

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5
Q

Bonds between sugar molecule and phosphodiester are ____while the bonds between nucleic acid pairs are ___.

A

Bonds between sugar molecule and phosphodiester are flexible while the bonds between nucleic acid pairs are fixed.

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6
Q

Bases choose their position according to :

A
  • Formation of optimal hydrophobic interaction between neighboured bp
  • Avoiding contact with functional groups of the vincity bp
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7
Q

Right-handed double helix

A

A-Form DNA and B-Form DNA

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8
Q

Left handed double helix

A

Z- From DNA

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9
Q

A- form DNA (Rare)

A
  • right handed
  • flexible but rigid DNA structure due to dehydration
  • major and minor grooves can be observed in each turn
  • 11 bp/helix turn
  • angle between two bases: 33.1 D
  • angle between bases and helix axis: 71-77 D
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10
Q

B- Form DNA (common)

A
  • right handed
  • major and minor grooves present alternatively
  • 10.4 - 10.5 bp/helix
  • angle between two bases: 35.9 D
  • angle between bases and helix axis: 90 D
  • narrower than A DNA
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11
Q

Z- Form DNA

A
  • left handed
  • zigzag appearance
  • recognition for binding of regulator proteins
  • 12 bp/ helix turn
  • angle between two bases: 60 D
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12
Q

What is positive supercoiling?

A

Positive supercoiling is over- wounded DNA.

  • more than 10.4 bp/turn (increase in linking number)
  • More difficult to separate the DNA
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13
Q

What is negative supercoiling?

A

Negative supercoiling is under-wounded DNA

  • less than 10.4bp/turn (decrease in linking number)
  • easier to separate DNA
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14
Q

Topoisomerase I

A
  • break one DNA strand, pass other strand though gap and reseal the nick
  • ATP not required
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15
Q

Topoisomerase II

A
  • break both DNA strands
  • energy required (ATP or NADH)
  • Gyrase (in bacteria)
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16
Q

Gyrase

A

Gyrase is Top II in bacteria which introduce negative supercoil

17
Q

What is hyperchromicity?

A

Hyperchromicity is increase in UV light absorption (260nm) in single stranded DNA than double stranded DNA

  • H-bond limits the resonance of the aromatic ring and limit the absorbance
  • hypochromic effect depends on GC content of DNA
18
Q

What is Tm?

A

Tm is temp at which 50% of the DNA strand is separated

19
Q

How is DNA denatured?

A
  • separate H-bond by heating or base addition
20
Q

How is DNA renatured?

A
  1. Nucleation: paired nucleotide sequence sequence meet each other
  2. fast reestablishment of double strand
21
Q

Velocity of DNA renaturation/ reassociation depends on. __

A
  1. concentration of cations to mask the negative charges of the phosphorus-group
  2. temp (optimal ~25 D celcius)
  3. size and concentration of DNA
22
Q

How many bp in human genome?

A

3000 million bp

3* 10^9

23
Q

Louis Pasteur

A

Life only develops only out of life

24
Q

Gregor Mendel

A

the law of heredity

25
Q

Ernst Haeckel

A

the nucleus is responsible for heredity

26
Q

Friedrich Miescher

A

discover that DNA is nucleus

27
Q

Griffith Avery, MaCarty and MacLeod

A

DNA could transform one type of bacteria into another type of bacteria

28
Q

Chargaff

A

Analyzed the relative amount of A,C,G, T in cells

- found A=T, C=G

29
Q

Hershey and Chase

A

DNA, not protein is the infectious agent in viruses

- T2 phage , DNA is labeled with 32P and Protein is labeled with 35S

30
Q

Watson and Chase

A

X-ray diffraction photo of DNA, double helix discovery

31
Q

Meselson and Stahl

A

Semi-conservative model of DNA replication (one new strand pair with one old strand)
- bacteria cultured in heavy nitrogen (15N) medium then transferred to light nitrogen (14N)
then centrifuged DNA sample

32
Q

What are 3 possible DNA replication mechanism?

A

Conservative model
Dispersive model
Semiconservative model

33
Q

Conservative model

A

the parental strand remain intact and a second new double strand is made

34
Q

Dispersive model

A

daughter strand contains segments of parental strand and segments of newly synthesised strand

35
Q

Semiconservative model

A

daughter strand consist of one new strand and one parental strand (each parental strand is used as template)

36
Q

What are two ways to prove semi-conservative model?

A
  • culturing bacteria in heavy nitrogen medium and then transferring to light nitrogen medium and centrifuging the DNA sample
  • sister chromatid staining (sister chromatid exchange and BrdU)
37
Q

Sister chromatid exchange

A

the exchange of genetic material between two identical sister chromatids

molecular genetic (2 decks)

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