Properties of DNA Flashcards

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1
Q

DNA melting & hybridisation

A
  • Although the secondary structure of DNA is stable, it can denature by treating it by alkali/acid or by heating
  • Temperature of melting varies from 65-80 degrees depending on G=C content (since most H bonds, 3, are broken)
  • If cooled slowly, DNA renatures (hybridises)
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2
Q

The Dimensions Of DNA

A
  • Diameter of helix is 2 nm
  • Adjacent bases are separated by 0.34nm + related by a rotation of 36 degrees
  • Helical structure repeats every 10 residues, 3.4nm ( 1 complete twist = 10 base pairs)
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3
Q

How to determine length of DNA molecules

A

By multiplying the number of base pairs by 0.34nm

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4
Q

Base pairs in human genome

A

3 x 10 ^9 bp

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5
Q

Chromosome sizes

A

50 x 10^6 to 250 x 10^6 bp

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6
Q

How is DNA packaged?

A

Into chromosomes using histone proteins 5 types)
- 2 copies of each come together to form a histone ocular
- Which forms a nucleosome , a cylinder that DNA can wrap around

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7
Q

How Chromosomes are folded

A
  • Folds into 30 nm fiber then to 300 nm fiber - is highly compacted
  • To replicate/transcribe DNA in the cell, it is in an organised compacted form
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8
Q

Epigenetics

A
  • DNA and histones can be modified
    e.g. DNA methylation of C residues or histones modified by also acetylation (silenced sequences to specify the cell type - genes not required for cell is methylated)
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9
Q

The effect of epigenetics

A
  • Doesn’t change DNA sequence but can regulate gene transcription
  • Changes can be passed during cell division and to future generations (epigenetic inheritance)
  • Key roles: development, aging (from methylation), cancer, behaviour + addiction
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